THE PLANT DISEASE REPORTER Issued By THE PLANT DISEASE SURVEY Division of Mycology and Disease Survey BUREAU OF PLANT INDUSTRY, SOILS, AND AGRICULTURAL ENGINEERING AGRICULTURAL RESEARCH ADMINISTRATION UNITED STAreS DEPARTMENT OF AGRICULTURE — VS. Number 2 Volume 36 February 15, 1952 The Plant Disease Reporter is issued as * service to plant pathologists throughout the United States. It contains reports, summaries, observations, and comments submitted voluntarily by qualified observers. These reports often are in the form of suggestions, queries, and opinions, frequently purely tentative, offered for consideration or discussion rather than as matters of established fect. In accepting and publishing this material the Division of Mycology and Disease Survey serves merely as an informational clearing house. It does not assume responsibility for the subject matter. THE NF Dt SE. A REPORTER Issued by THE PLANT DISEASE SURVEY DIVISION OF MYCOLOGY AND DISEASE SURVEY Plant Industry Station Beltsville, Maryland Volume 36 February 15, 1952 Number 2 IN THIS ISSUE Eric G. Sharvelle reviews and discusses British investigations on systemic fungicides, page 35. Establishment of many important bean diseases since commercial production began on newly irrigated lands in the Columbia Basin area of central Washington emphasizes the importance of disease-free seed and of initiation of a system of rotation before the new land can become contaminated, according to J. D. Menzies, page 44. Experimental evidence on the relation of two viruses to symptom expression in gladiolus is reported by Philip Brierley, page 48. D. C. Torgeson reports occurrence of Verticillium on geranium in Oregon, page 51. William W. Diehl identifies the powdery mildew attacking kenaf, a potentially valuable new fiber crop for Florida, page 52. Occurrence of Thielaviopsis root rot of cotton in Upper Rio Grande Valley of Texas supports the conclusion that the causal fungus is indigenous to the soils of the arid Southwest, according to Philip J. Leyendecker, Jr., page 53, A. L. Taylor reports experimental infection of tomato roots with a Heterodera indistinguish- able from the potato golden-nematode, obtained from tobacco roots and from soil from a tobac- co field in Connecticut, page 54. William W. Diehl lists additions and corrections to his previous report on Balansia and the Balansiae, page 55. Definite indications of protection against rodents afforded by corn seed treatment with Arasan are reported by Jack F. Welch and Millard Graham, page 57, Incidence of legume and grass diseases in North Carolina in 1950 and 1951 is reported by J. Lewis Allison, et al., page 60. Infection of flowers of alfalfa, sweetclover, and red clover by Botrytis is reported by Fred Reuel Jones, page 61. Swellings on pine twigs associated with Cucurbitaria pithyophila actually are due to a scale insect on which the fungus develops, according to J. S. Boyce, page 62. George H. Hepting et al. send a further note on perithecial production in the oak wilt fungus, page 64, Accidental spraying of horsechestnut with 2, 4-D resulted in viruslike symptoms described by F. P. Hubert, et al., page 65. The "unknown disease" of coconut palms in the West Indies actually is due to toxic compounds in the soil, even though at times it gives every indication of virulent infectious spread, according to Henning P. Hansen, who suggests an explanation for the apparent spreading nature of the dis- ease, page 66. Unusual records and other brief notes, page 68, contain reports on the oak wilt survey in Kansas, by Ivan J. Shields; control of bacterial leaf spot of peach with mercury sprays, by R. S. Kirby; occurrence of tomato spotted wilt in Maryland, by John J. Smoot; incidence of foliage diseases of cucurbits in the Lower Rio Grande Valley in 1951, by G. H. Godfrey; occurrence of oat diseases in Minnesota in 1951, by S. Goto and M. B. Moore, A correction, page 70. December weather, page 71. gicic lizec sabc tary tiall The: (e.g necr appl infec grov luxu: farm for t the r the s in A chea A. thu: Erv siol Am plat Sinc phy fort met will che: wly Vol, 36, No, 2--PLANT DISEASE REPORTER--Feb, 15, 1952 35 SYSTEMIC FUNGICIDES IN 1951: BRITISH INVESTIGATIONS Eric G. Sharvelle The growth of the profession of plant pathology as an autonymous science dates in the U. S. A. from the establishment of the Division of Vegetable Patnology and Plant Physiology by the U. S. Department of Agriculture in 1885, From this beginning, pioneered by the foresight and en- thusiasm of American fathers of phytopathology such as B. T. Galloway, Walter T. Swingle, Erwin F. Smith, and others, phytopathology in 1952 has become a recognized and skilled profes- sion entrusted with the responsibility of contributing its share to the security and well-being of America's vast agricultural industry. In the early days pioneers in phytopathology of necessity mostly confined their efforts to the task of trying to discover "Why do plants get sick?" The etiological approach to the study of plant diseases dominated American phytopathology for the first two decades of the 20th century. Since that time, having been provided with a foundation of basic principles by this early work, phytopathologists have devoted more and more of their efforts to the task of growing healthy crops. Dating from approximately 1934, when organic fungicides became fashionable, strenuous ef- forts have been made by sciences and industry to develop more effective and more economical methods of reducing crop losses caused by plant diseases, That plant disease control in 1952 will be "big business" is evidenced by the "guesstimates" of the annual consumption of fungicidal chemicals in the United States, summarized in Table l. Table 1. Summary of fungicidal chemicals used annually in the United States. Material Pounds consumed Sulphur (all forms) 180, 000, 000 Copper (all forms) 21, 000, 000 Copper sulfate 84, 000, 000 Mercury (as metallic) 152, 000 Organic mercurials 85, 000 Bichloride of mercury 59, 000 Quinonea 2, 000, 000 Heterocyclic nitrogen compounds 1, 000, 000 Carbamates 8, 000, 000 212, 152, 000 It is doubtless a safe conservative estimate that the annual United States consumption of fun- gicidal chemicals is in excess of 200 million pounds of chemicals. All of these materials are uti- lized by America's agricultural industry in the form of insurance against the ravages of the crop saboteurs constituted by the diseases of growing plants. The strange sounding names of proprie- tary fungicides with their long handled chemical formulations used in 1951 were at best only par- tially effective and not entirely economical weapons in our arsenal of defense against crop enemies. There still remain several plant diseases for which there is no known practical fungicidal remedy (e.g., fireblight of apples, carnation Fusarium wilt, bacterial leaf spot of stone fruits, phloem necrosis, oak wilt, etc.) Most of the currently popular fungicidal chemicals are protective in nature, requiring their application in advance of the disease and constant renewal of the protective blanket throughout the infection periods for the disease in question. In 1952 there will be many peach, apple, and potato growers, and other specialized agriculturists who will be asking "Can we continue to afford the luxury of 'complete spray schedules'?", so long as prices for agricultural commodities on the farm continue to lag behind cost of living indices. Protective fungicides are expensive remedies for the ills of growing plants. Furthermore, the effectiveness of these materials is predicated by the necessity for proper timing, efficient coverage and constant renewal of the protective film, and the selection of the most effective material for the problem concerned. Economic considerations in American agriculture in 1952 are, as they should be, influencing phytopathologists to look for cheaper ways of effectively controlling plant disease losses. 4 ish- isan d us, 1 inds ing - e 36 Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 Systemic plant protection is a new and intriguing approach to the perplexing problem of limiting plant disease losses. It is not unlikely that 1952 may be recorded in the annals of phytopathology as the year in which "systemic plant disease control" became popular. Before reviewing the British investigations on systemic fungicides it is justifiable to con- sider briefly the methods at present employed for the limitation of economic plant diseases. The current methods of controlling plant diseases have been erected on the foundation laid by pioneer workers on their nature and cause. Plant disease control is effectuated by the appli- cation of four principles or by combinations of these major categories (Figure 1). Growing crops may be kept healthy by protecting them with chemical specifics which can be applied ex- ternally or internally. Recent research has also suggested that certain chemicals may be in- troduced into the plant system, resulting in immunization against certain phytopathogens. Im- munization by "gene juggling" to produce resistant crop varieties is a major, and in some cases sole, method of combatting plant diseases practicably. Eradication of plant diseases by elimi- nation of alternate hosts, primary sources of inoculum, initial infections, or roguing out of sick individuals is recognized by every phytopathologist as a basic principle of plant disease con- trol. Finally, legislation or regulatory measures designed to keep out or limit plant diseases have been adopted by most States of the Union and is currently being considered as a possible weapon in national defense. PLANT DISEASE CONTROL ERADICATION LEGISLATION GENETICAL FIGURE 1. The principles of Plant Disease Control. Chemical plant protection is the major interest of this discussion. Chemicals capable of inactivating, inhibiting, or otherwise discouraging phytopathogens may be applied to the surface of plant parts susceptible to infection, or they may be introduced or absorbed into the plant cells or the transpiration stream to serve as systemic protectants (Figure 2). CHEMICAL PLANT PROTECTION SURFACE SYSTEMIC PROTECTION PROTECTION FIGURE 2. The nature of Chemical Plant Disease Protection. Surface protectants are constituted by the many furgicidal, non-phytotoxic chemicals that are employed as seed protectants (Figure 3). These are the modern fungicides of 1952 that comprise the 200 million pounds of chemicals used by the American agricultural industry. SURFACE PLANT PROTECTION SEED FOLIAGE FRUIT PROTECTION PROTECTION PROTECTION FIGURE 3, The nature of Surface Plant Disease Protection. ul P tre fe: to it lis m la re m qu cl in st ha pe ci thi ab ro = to ch su co cu IN lls ire Sse Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 37 Few developments in the application of research to agricultural practice have had a greater appeal to the popular imagination than the systemic fungicides about which we are now beginning to hear. The idea that by applying a chemical to the roots or some aerial part or by injecting it into the tissues of a crop plant, it is possible to induce resistance to or to eliminate estab- lished phytopathogens without harming the plant itself or affecting the usability of its products, must perforce conjure up visions of almost boundless applications in the future. This is the layman's reaction to the topic of systemic plant protection. Systemic plant protection in some respects is the parallel in the realm of plant hygiene to some of the almost miraculous develop- ments which have occurred in human and animal pathology; as examples may be cited the use of quinine, atabrin, and more recently paludrin in malarial prophylaxis and treatment. The mira- cle drugs, Streptomycin, Aureomycin, Clavicin, and Penicillin are examples of modern progress in combatting bacterial pathogens in animals and human beings. In both cases the protective substance is translocated within the individual, in the case of vertebrate animals in the blood stream and in the case of plants in the sap stream. One might be justified in wondering why such advances in the realm of plant intents have lagged so far behind those in animal physiology. There are, however, a number of im- portant differences in systemic protection in plants and animals; for one thing, the blood stream circulates rapidly in healthy animals by virtue of the heart's action, and the relatively high and uniform temperature of the blood stream is conducive to rapid, extended, and uniform action on the infected material. In the case of plants, however, movements of the sap stream are brought about mostly by osmosis and are much slower, and the temperature varies with that of the sur- rounding environment. Systemic plant disease protection refers to the use of chemical agencies applied to plants to immunize them against disease or to cure them of troubles already established (Figure 4). Artificial immunization or chemical prophylaxis refers to the introduction of translocatable chemicals into the healthy plant system prior to entrance of the parasite into the host with re- sultant immunity to subsequent infection. SYSTEMIC PLANT PROTECTION CHEMICAL PROPHYLAXIS CHEMOTHERAPY NUTRITIONAL ANTIPARASITIC ANTIPATHOGENIC FIGURE 4, The nature of systemic Plant Disease Protection. C. G. Zentmeyer (1942) demonstrated that the severity of Dutch elm disease (Ceratostomella ulmi) could be limited or reduced by pre-inoculation injections of hydraquinone, benzoic acid, or P-nitrophenol, Similarly, Dimock (1944) reported control of foliar nematodes by pre-inoculation treatment of soil with sodium selenate,. Chemical prophylaxis could theoretically be effectuated by: 1. Foliage application and leaf absorption. 2. Soil treatments and root absorption. 3. Injection and translocation. Chemotherapy as contrasted with chemical prophylaxis refers to the cure of plant diseases already established by means of internal chemical treatments. The term appears to have been coined by Ehrlich in 1913 in his classical researches on organic compounds of arsenic for the cure of human syphilis. Chemotherapy in its present state of phytopathological immaturity of- fers promise for the cure of three types of plant disorders. 1. The cure of physiological disorders initiated by nutritional deficiencies. . a. Zinc deficiency in citrus trees. b. Manganese deficiency in soybeans. c. Oak tree chlorosis caused by iron deficiency. d. Foliage sprays for the correction of copper, boron, and other minor element deficiencies. 38 Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb, 15, 1952 2. Antiparasitic chemotherapy, in which a selective fungicide or highly specific chemical agency is introduced into an infected plant system with the purpose of curing the trouble without damage to the host plant or its products. a. The use of natriphene (sodium salt of ortho-hydroxydiphenyl) for the control and cure of Rhizoctonia damping-off. b. Inactivation of peach 'X" disease virus by the use of emanate derivatives, 3. Antipathogenic chemotherapy, in which chemicals are introduced to neutralize or anti- dote toxins responsible for plant disease symptoms. a. Curing of bleeding canker of maple (Phytophthora cactorum ) by the use of diamino. azobenzene dihydrochloride. b. Antidoting the toxins of Dutch elm disease (Ceratostomella ulmi) by injections of oxyquinoline-benzoate, c. Inactivation of carnation Fusarium wilt (Fusarium oxysporum f, dianthi ) by soil applications of carbamates. British Investigations in Systemic Plant Disease Protection It is recognized that American workers have pioneered the field of systemic plant disease protection, It is the purpose of this discussion to summarize briefly the contributions of British workers in this new and intriguing phase of plant disease prevention. The British work in systemic plant disease protection is considered by the workers them- selves as essentially preliminary in nature and has been directed mainly towards demonstrating that certain translocatable chemical compounds are potentially useful as systemic fungicides, and towards developing a technique for investigating this activity. The British work has been stimulated by five workers in four separate institutions: R. W. Marsh and Steven H. Crowdy at the University of Bristol Agricultural Research Station; R. L. Wain, at Wye Agricultural College, near Ashford, Kent; W. G. Keyworth, at East Malling Fruit Research Station, East Malling, Kent; and P. W. Brian, of the Imperial Chemical Industries Ltd., Butterwick Research Laboratories, Welwyn Garden City, Herts. The British work on systemic fungicides has from the outset been based on the following premise: "There are two obvious starting points in a search for a systemic fungicide: (a) To sur- vey known fungicides for systemic properties. (b) To examine the effect on fungi of compounds known to be translocated in higher plants.'"' The second line of approach is the attack that has been adopted by the British workers. Plant Growth Substances as Systemic Fungicides In 1948 Steven Crowdy reported on the effects of plant growth substances on the growth in culture of the apple canker fungus Nectria galligena Bres. (1) In this early work, Crowdy studied the daily rate of growth of this fungus by comparing the dry weight of cultures grown in nutrient selections containing varying concentrations of several growth substances, Since the toxicity of substances such as these increases with acidity, the culture media were buffered to a constant pH (Table 2). None of these growth substances were strongly fungicidal, and although the more toxic produced a marked reduction in growth in relatively small concentrations, growth was not completely inhibited at much higher concentrations. For this reason, in liquid culture the toxic concentration was considered to be the quantity of chemical required to reduce growth to less than 5 percent of the controls. The chemicals used in this preliminary work are known as aryloxyali- phatic acids, which are known to be translocatable in plants, From these preliminary results, it is apparent that certain aryloxyaliphatic acids do possess fungicidal value. The results further suggested that the napthoxy acids were, in general, more fungicidal than the phenoxy acids and that increasing chlorine substitution in the nucleus resulted in greater toxicity, In 1950, Crowdy and Wain (2) reported on future studies on the systemic fungicidal value of aryloxyaliphatic acids. In their work, they were concerned with the possible value of aryloxyali- phatic acids as inhibitors of Botrytis cinerea, the causal organism of the chocolate-spot disease of broad bean (Vicia faba). Preliminary laboratory tests indicated that the aryloxyaliphatic acids were also toxic to Botrytis cinerea. Most of the trials with these materials as systemic fungicides reported by Crowdy and Wain in 1950 were carried out on young bean seedlings grown for two to three weeks with their roots immersed in solutions containing 10 p.p.m. of the acids: in addition the stems of larger potted plants of Vicia faba were injected with solutions of the same strength. After treatment the plants were sprayed with a heavy suspension of spores of Botrytis cinerea and were kept in a saturated atmosphere until chocolate-spot symptoms developed, in approximate- r a A d N b a V Pp tl a tl Ww te Ww gi tr le 1ino: sh ur- lied Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb, 15, 1952 39 ly three days; the disease damage to each leaf was then assessed by using an arbitrary disease- rating scale. Table 2, The effect of plant-growth substances on the growth of Nectria galligena. Substance Growth rate Toxic concentration (used at rate of 100 ppm) (mm, per day) on 2% in ppm in liquid cul- malt agar-pH, 4.8 ture pH. 3.8 2, 4, 6-Trichlorophenoxyacetic acid 1.22 + 0.07 40 1-Chloro-2-naphthoxyacetic acid 1.07 + 0.02 40 alpha-Naphthaleneacetic acid 1.40+ 0.05 20 beta-Indolbutyric acid 2.374 0.11 60 beta-Indolylacetic acid 2.594 0.04 100 beta- Naphthoxyacetic acid 2.67 + 0.16 60 2, 4-Dichlorophenoxyacetic acid 2.20+ 0.09 80 Control 3.01 + 0,09 -- These experiments demonstrated that 2, 4,6-Trichlorophenoxyacetic acid gave a consistent reduction in disease development. In five separate trials with bean seedlings the mean percent- age disease reduction recorded with this chemical was 36. It appeared that the effect of the treat. ment was to check the spread of the individual lesions rather than to prevent lesion formation, A number of other acids were also studied and found to be capable of inhibiting chocolate-spot disease in bean seedlings whose roots had been immersed for two weeks in 10 p.p.m. of the acids concerned. Significant reduction in disease development was obtained with the following acids in preliminary trials: Pentachlorophenoxyacetic acid Pentachlorophenoxyisobutyric acid alpha (2-Naphthoxy)-phenylacetic acid None of the above acids caused damage at the concentrations used. 2, 4, 5-Trichlorophenoxyiso- butyric acid reduced the extent of disease somewhat when injected into the stem, but caused damage when roots of seedlings were immersed in 10 p.p.m. of this acid for two ‘weeks, and the seedlings treated in this manner showed no reduction in disease development. In 1951 Crowdy and Wain (3) published the de.ailed results of their preliminary work on aryloxyalkylcarboxylic acids as systemic fungicides for the inhibition of Botrytis cinerea on Vicia faba. The results of these studies confirmed and amplified the preliminary studies re- ported in 1950. The authors describe in detail a method for assessing the systemic activity of compounds for the suppression of foliage diseases, including an excellent technic for recording the extent of disease development. In this work, also, the roots of broad bean seedlings were allowed to stand in a solution containing 10 p.p.m. of the chemical for two to three weeks. As in the previous work, treated seedlings were inoculated by spraying both surfaces of the leaves with a spore suspension of B. cinerea in a 1% dextrose solution until they were thoroughly wet- ted or dripping. All of the plants in any one trial were sprayed with the same spore suspension, which combined with the thorough soaking provided a uniform inoculation within the trial. A number of compounds were found to be ineffective, including: 2-Chlorophenoxyacetic acid 2, 6-Dichlorophenoxyacetic acid 2, 4, 6-Tribromophenoxyacetic acid ** 1, 4-Dichloro-2-naphthoxyacetic acid alpha-Phenoxyphenylacetic acid ** beta (1-Naphthoxy) propionic acid 3-Chloro-4-iodo-5-Bromobenzoic acid ** ** caused damage to the plants The performance of the successful compounds is summarized in Table 3. The disease reduction given by these three materials was statistically highly significant and they were harmless to the treated plants, In one trial the same three acids gave reduction of 45, 22, and 22 percent re- spectively when applied at only 1 p.p.m. of ig 1it t of e ic than li- her 1 f li- ids tides on iate- 40 Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb, 15, 1952 Table 3. Reduction in chocolate-spot disease following root treatment with acids at a con- centration of 10 ppm. Compound used : Percentage disease reduction : Number of trials : Mean : Max. : Min. 2, 4, 6-Trichlorophenoxyacetic acid 15 37 62 11 2, 3,4, 5, 6-Pentachlorophenoxyacetic acid 7 33 46 20 2,3, 4, 5, 6-Pentachlorophenoxyisobutyric acid ei 27 54 7 Since these materials were effective when used as root treatments their effect when applied to the soil was also studied. Bean seedlings were grown in pots of sterilized soil and were watered with solutions of the acids at a concentration of 50 p.p.m. instead of water for three weeks prior to inoculations. The results are given in Table 4. The effect of the treatments was to build up a concentration of approximately 100 p.p.m. by weight of the acid in the soil. The disease reductions obtained with phenoxy acids in Table 4 were all statistically significant with the exception of 2, 4, 5-Tri- chlorophenoxyisobutyric acid, in which case the weakening effect on the plants following root damage probably offset any beneficial effects of the treatment. Additional work indicated that the rate of uptake of compounds such as trichlorophenoxyacetic acid from the soil was very rapid, since soil applications one day before inoculation resulted in 63 percent disease control. Further- more there appeared to be no noticeable tendency for the materials to accumulate in the plant tissues. Studies of the persistence of these compounds in the soil demonstrated that they remain active for considerable periods of time. An application of 100 p.p.m. of 2, 4, 6-Trichlorophenoxy- acetic acid 140 days before seedlings were planted and inoculated with _B. cinerea still gave a significant reduction in disease assessment. Table 4, The effect of adding phenoxy acids to the soil on the development of Botrytis cinerea on Vicia faba. Compound used Disease assessment Percentage control 2, 4, 6-Trichlorophenoxyacetic acid 55 2, 4, 5-Trichlorophenoxyisobutyric acid 83 Pentachlorophenoxyacetic acid 49 Pentachlorophenoxyisobutyric acid 51 1-Phenyl-3, 5-Dimethyl-4-nitrosopyrazole 79 ** Caused damage to plants Crowdy and Wain also investigated the possibility of induced chemical prophylaxis for the inhibition of chocolate spot of broad beans by means of spray applications of phenoxy acids to the foliage. If single stems only of double-stemmed plants are sprayed and a significant re- duction in disease development results on the unsprayed half of such a plant, it is logical to suggest that a systemic effect is established. A negative result, on the other hand, does not necessarily mean that the compound has not been absorbed but may simply mean a failure in translocation, With this in mind, a number of double-stemmed plants were sprayed with 500 p.p.m. of 2, 4, 6-Trichlorophenoxyaceticacid with a 0.5 percent wetting agent added. A cor- responding number of controls were sprayed at the same time with the wetting agent alone, The plants were inoculated four days after spraying and the disease assessments were made three days after inoculation. The results of this trial are given in Table 5. These results indicated that there was no significant difference of any magnitude in the num- ber of lesions although the numerical difference suggested a possible protective effect from the spraying. The lesion measurements, however, show definite evidence of a systemic effect. Lim- ited field trials in which a number of plants were sprayed with 500 p.p.m. of 2, 4, 6-Trichloro- sh ¢ ph vid Br col He mi als ac. prt car cor tio: is | in Gr val of Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb., 15, 1952 41 phenoxyacetic acid gave a significant reduction of 41 percent in the number of inflorescences shed as a result of chocolate spot disease. Table 5. Effect of spraying Vicia faba with 2, 4, 6-Trichlorophenoxyacetic acid on the development of Botrytis cinerea, using double-stemmed plants. Treatment Number of lesions Mean diameter of lesions 2, 4, 6-Trichlorophenoxyacetic acid A. Sprayed side 9.4 21,1 B. Unsprayed side 17.8 23.4 0.5 percent wetting agent alone A. Sprayed side 15.1 26.1 B. Unsprayed side 25.5 26.3 Sign. diff. at P=0.05 Lesion count 8.3 Lesion diameter 1.38 Antibiotics as Systemic Fungicides Another fascinating approach to the problem of systemic plant disease protection is pro- vided by the work of P. W. Brian and his associates of the Imperial Chemical Industries Ltd. Brian is recognized internationally for his outstanding contributions to the field of knowledge concerning antifungal substances produced by fungi and other microorganisms (antibiotics). He has also contributed much to microbiologists' knowledge of the production of antibiotics by microorganisms in relation to biological equilibria in the soil. Brian and his associates have also made noteworthy additions to our knowledge of antibiotics such as Frequentin, Gladiolic acid, Alternaric acid, Glutinosin, Viridin, and Griseofulvin. Very recently Brian has reported preliminary results on the systemic value of Griseofulvin as a preventative for tomato foliage diseases. Griseofulvin is the antifungal compound produced by Penicillium nigricans (Bainier) Thom (=_P. janczewski Zal) as well as by the less common P. griseo-fulvum Dierckx. Griseofulvin (C,7H;70,gCl) has the postulated structure: 6 OCH, OCHs | | Cc C=O Experiments with lettuce, oats, and tomato seedlings have demonstrated that this compound can be absorbed through the roots or leaves and is readily translocated throughout the plant. The compound is stable in aqueous solutions and can easily be detected specifically in low concentra- tions by a bioassay based on its unique effect on tne morphogenesis of some plants, Griseofulvin is known to have marked fungistatic properties although it has never been thought to be fungicidal in the strict sense of the word. In 1951 Brian published the results of his preliminary work on the systemic properties of Griseofulvin as a preventative for Alternaria solani on tomatoes (4). Potted tomato plants of the variety "Best of All" were grown in sand culture. Treated plants were watered daily with 50 ml of a 100 ugm/ml of griseofulvin in 2% aqueous acetone, A similar series of potted plants received 42 Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb. 15, 1952 similar treatments with tap water. Both series were also given an additional daily watering with 50 ml of culture solution. On the fifth day all of the plants were inoculated by aptaging with an aqueous suspension of spores of Alternaria solani, using a spore load of 25 x 10° spores per milliliter, The plants were then kept in a humidity cabinet at 98 to 100 percent relative humidity for 24 hours before being returned to the greenhouse. The number of lesions pro- duced on the 25 main leaflets of the lower five leaves of each plant were then counted two days later. The result of one of these trials is given in Table 6, Table 6. The value of Griseofulvin as a systemic fungicide for the prevention of Alternaria solani on potted tomato plants. Treatment : Replicate lesion counts ; Total : Disease: Disease : Bp : Cc : lesions: percent : control (percent) Griseofulvin 127 486 133 764 26 74 Control T¥9 880 1289 2944 100 0 From the results of these experiments Brian concluded that griseofulvin showed undoubted activity as a systemic fungicide. In recent correspondence Dr. Brian stated, '"We have only published a preliminary account of the systemic fungicidal activity of Griseofulvin, although we demonstrated it to a meeting of the Association of Applied Biologists, held at our laboratories on June 1, 1951. Since our preliminary results were published we have confirmed many times over the control of Alternaria solani on tomato by the technic described, and using 0.05 per- cent griseofulvin in the nutrient solution obtain almost perfect prevention of A. solani attack, We have also had reports of equally good control of mildew of barley (Erysiphe graminis) and of Botrytis fabae on broad beans. A small sample of griseofulvin has been passed on to Hors- fall by Wain so that the results of American tests should soon be available. Please quote any of this information. "We are getting more workers on to the systemic fungicide problem and the next time you are here we should have a lot more to show." Summary 1. Systemic plant disease protection is the use of chemical agencies which are applied to plants to immunize them against disease or to cure them of diseases already established. 2. The British work in this field has been confined to the effect on fungi of compounds known to be translocated in higher plants. The British workers themselves consider their ef- forts entirely preliminary and are currently primarily interested in developing suitable technics for investigating the potential use as systemic fungicides of certain translocatable chemical compounds, 3. Crowdy and Wain have demonstrated that certain aryloxyaliphatic acids will inhibit the development of chocolate spot disease (Botrytis cinerea) when applied to potted plants as root treatments, soil applications, or in the form of foliage sprays. 4, Brian has demonstrated that the antifungal compound "Griseofulvin" will prevent the development of Alternaria solani when applied as a foliage spray or as a watering material for potted tomato plants. 5. We have as yet but peeked through the keyhole of the door of systemic plant disease pro- tection. Much remains to be done before this door to fascinating possibility is thrust open for the practical agriculturists. 6. Biologists at present are seeking for suitable tools to "jimmy" open this door to systemic plant protection, and preliminary findings would suggest that the view behind the closed door is well worth the seeking. It is to be hoped indeed that 1952 will be the year in which phytopatholo- gists and workers in related fields will be able to offer to American agriculture "pink pills for pale plants."' Further, it is but logical and progressive to conclude that the greatest progress in this field will accrue only from wholehearted cooperation between American workers in this field and those who strive for the same end across the seas. Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb, 15, 1952 43 "Wars have come and gone but the world of fascinating romance, the romance of chemical compounds and reactions is still luring men's minds and leading the curious on into still vaster and more incredible things. Fungicides are indeed those remedies without which our horti- culture would never have become what it now is, the source of that element which Plato declared was the most important of them all in the building of a state - FOOD," David Fairchild. Literature Cited 1. Crowdy, S. H. Treatment of apple canker lesions with plant-growth substances, Nature 161: 320. 1948. 2. and R. L. Wain. Aryloxyaliphatic acids as systemic fungicides, Nature 165: 937. 1950. 3. . Studies on systemic fungicides I, Fungicidal proper- ties of the aryloxyalkylcarboxylic acids. Annals. App. Biol. 38: 318-333. 1951. 4, Brian, P. W., Joyce M. Wright, J. Stubbs, and Audry M. May. Uptake of antibiotic metabolites of soil organisms by plants. Nature 167: 347, 1951. PURDUE UNIVERSITY, LAFAYETTE, INDIANA 4 = c 44 Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 OBSERVATIONS ON THE INTRODUCTION AND SPREAD OF BEAN DISEASES INTO NEWLY IRRIGATED AREAS OF THE COLUMBIA BASIN 1 J. D. Menzies When large areas of new land are made available for irrigated farming by new reclamation projects, freedom from plant diseases is an advantage that may be expected. How long this in- itial disease-free state can be maintained is of great importance. The following observations on newly irrigated lands of the Columbia Basin area of Washington show, in the case of field beans, how quickly major diseases can become established. Field beans were not grown commercially in irrigated central Washington prior to 1947 following the opening of new lands of the Roza Project in the Yakima Valley. In the last five years bean acreage has increased rapidly on both new and old land, reaching an estimated 15,000 acres in 1951. Thus, beans are not only new to the recently developed irrigation pro- jects but new to the surrounding older projects. The parasitic diseases appearing in sucha crop are either due to introduced pathogens or to the transfer of established pathogens onto a new host, In the latter case the pathogens may be native on the wild vegetation or previously introduced on other crops in the older irrigated areas. In the first five years of the dry bean industry of newly irrigated areas of Washington the following diseases have made their appearance: Disease Cause Fusarium root rot Fusarium sp. Sclerotinia rot Sclerotinia sclerotiorum Rhizoctonia root rot Rhizoctonia solani Pythium wilt Pythium butleri Common bacterial blight Xanthomonas phaseoli Halo blight Pseudomonas phaseolicola Bacterial wilt Corynebacterium flaccumfaciens Rust Uromyces phaseoli var. typica Botrytis rot Botrytis sp. Yellow Mosaic Virus Common bean mosaic Virus New York 15 mosaic Virus Curly top Virus Identifications have been made or confirmed by Dr. W. J. Zaumeyer and Dr. H. R. Thomas who have also collaborated in many of the observations noted below. Fusarium Root Rot. This disease behaves as though the pathogen were native in the area. The pattern of development is the same whether on old land or on new land that may even be iso- lated and irrigated from deep wells. Root rot typically increases from a trace the first year to serious damage the third year when beans are grown continuously. Very few instances of healthy beans in the third consecutive year have been seen. When root rot begins to cause dam- age ina crop, growers adopt the practice of continuous irrigation. This stimulates new root production and in most cases brings the crop through with a reasonable yield. Sclerotinia Rot. The pathogen Sclerotinia sclerotiorum had not been reported in the Yakima Valley prior to 1947, That summer a few infected bean plants were found in a single field on the Roza Project. The next year minor damage was noted on many other fields while serious dam- age occurred in the field where the disease was found the year before. Sclerotinia rot is favored by heavy vine growth. The usual type of damage is rotting of vines and pods in contact with the ground. A more serious type of damage, where entire plants are killed in circular areas in the field, has recently been noted, Since the beans are dried in the field and combined, the sclerotia, infected plant parts, and damaged seeds are broadcast thoroughly over the field as inoculum for next year. This disease is now well established in the Yakima Valley, the Pasco project, and to a lesser extent in the Moses Lake area of the Columbia Basin, Rhizoctonia Root Rot, This disease has so far attracted little attention, being much less T Pathologist, Division of Soil Management and Irrigation, U.S. Department of Agriculture, Irrigation Experiment Station, Prosser, Washington, de | pz be e1 m bl ur to nc is oc in ay In E Cz ti si sé Pp! ti o! in pe th r le be of cl gi ut fu li bi kr rere fr m T be m Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 45 prevalent than the two listed above. Its significance in the bean disease picture is not yet determined, Pythium Wilt. This disease is caused by Pythium butleri, which may be another native pathogen. It is usually found affecting only scattered plants and may be just as prevalent in beans on new soil the first year as it is in succeeding bean crops. This disease is not consid- ered to be of economic importance now but it has potential dangers. Bacterial Blight and Halo Blight. These two diseases can be considered together, They made their first appearance in Central Washington during the wet season of 1947. Common blight can now be found each year in trace amounts, but only, it should be stressed, on beans under sprinkler irrigation. The usual season in this climate is too dry to allow bacterial blight to spread when the crop is furrow-irrigated. Even the artificial rainfall from sprinklers has not been sufficient to cause an early build-up of blight. The typical blight picture under sprinklers is late-season leaf infection becoming general close to harvest time. Very few pod infections occur. Halo blight is of minor importance because of the arid climate and because of resistance in the major varieties now grown. Bacterial Wilt. This disease was first recorded in central Washington in 1951, From the available records of seed sources it seems probable that some seed fields were infected in 1950, In furrow-irrigated fields where this disease was seen, only single isolated plants were involved. Evidently these plants originated from infected seed and no secondary infections occurred. One case of this disease under sprinkler irrigation was observed and here a more serious situa- tion existed. Secondary infections were common on leaves, stems, and pods, Sometimes con- siderable pod infection could be found with little evidence of leaf infection. Such cases might easily be overlooked in inspecting seed fields or the secondary infection could occur late in the season after field inspection. Rust. A single case of rust infection was found in 1951 in sprinkled beans on the Pasco project. This is the first record of bean rust in central Washington. The details of this oc- currence are of interest in speculating on the source of inoculum. The field, in fact the en- tire farm, was plowed out of sage brush in late spring of 1951. The farm was isolated on the southern edge of the project. The operator used new equipment and no other beans were grown on the farm. When rust was first discovered in this field it was found to radiate from a single infection center near the middle of the field. These circumstances suggest that infected plant parts may have come in with the seed. The build-up of secondary infections occurred so late that there was no serious loss, Prior to this observation it was generally assumed that bean rust would never be a problem in the Columbia Basin area. It may still prove to be no prob- lem on furrow-irrigated beans but this occurrence illustrates a danger from rust in sprinkled beans. Botrytis Rot. Rots due to Botrytis sp. are not new to this area nor is the damage on beans of much importance, The injury is confined to stems and pods in cases where heavy foliage lies close to the ground. Botrytis infection seems to occur under these conditions, whether on new ground or on land cropped to beans for several years. It seems to be a case of a widely distrib- uted but not very aggressive pathogen. Virus Diseases. The bean viruses present a situation quite different from the bacterial and fungus diseases since insect vectors are of major importance in their spread. There is less likelihood of finding freedom from these diseases associated with new land because of the mo- bility of the insects involved. There is, however, the source of virus to consider. As far as is known now the only bean viruses present in this area that may transmit through the seed are common mosaic and its variant, New York 15 mosaic. The others listed below must originate from other hosts. Yellow bean mosaics have been noted in varying severity every year. Sweetclover, a com- mon roadside weed throughout the area, and red clover are probably the sources of the virus. The disease is of economic importance in many cases but no control measures are yet available. The variant or New York 15 strain of common bean mosaic is very widely distributed in the bean crops throughout the Columbia Basin, being more than usually prevalent in 1951. Since this virus is seed borne and no other hosts are known, the seed used is believed to be the pri- mary source of infection. Secondary spread occurs through the feeding activities of several 46 Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb., 15, 1952 species of aphids and perhaps by mechanical transmission. Secondary infections are often much more prevalent at the ends of the rows than farther into the field. This zone of heavy infection may be only 15 or 20 feet wide. The reason for this border effect is not clear. Aphids may be more prevalent at the field borders and also there is likely to be more mechanical contact be- tween plants and tillage equipment in turning at the ends of the rows. The type strain of common bean mosaic has been found on snap bean varieties susceptible to it. Curly top is a good example of an indigenous disease. Not only is the virus established in the sage brush areas on native hosts, but the leafhopper vector overwinters and builds up spring generations on the wild vegetation. No freedom from curly-top can therefore be expected in new- ly irrigated areas. In fact, the damage is likely to be more serious in the development years of new projects because of the proximity of native breeding areas of the insect vector. Unless wide- spread control of the leafhopper by insecticides becomes feasible, the only resort is curly-top- resistant varieties. Fortunately such varieties of beans are available and have made the bean in- dustry of this area possible. Discussion The incidence of new bean diseases in the newly irrigated areas of the Columbia Basin il- lustrates several important features of plant disease control. It provides data for predicting what can be expected in the normal course of new project development as to the speed of intro- duction and spread of the diseases and the possibilities of slowing down this process. The source of seed is perhaps of first importance. From the observations listed above it is probable that infected or contaminated seed was the original source of Sclerotinia rot, bac- terial blight, halo blight, bacterial wilt, rust and New York 15 mosaic. As far as is known, all the original seed stocks brought into the State at the start of the Washington bean industry were certified. It is discouraging to find, therefore, such a quick build-up of diseases previously un- known in the area. If disease-free seed is to be recommended as a means of excluding certain diseases from new land it will probably be necessary to go beyond the usual "certified" standards. In the case of the Columbia Basin area it is still not too late todo this. The best seed available could be in- creased in isolation on new land, without sprinkler irrigation and under strict inspection. The resulting crop could then be used as foundation stock for certified seed production on new ground within the area. The number of years of disease freedom which might be gained in this way could be increased by some kind of a quarantine restriction for the seed-producing area. Where exclusionary measures break down, or are not applicable, the next step in disease con trol is crop rotation. The results of the few years of bean growing described above have demon- strated the need for rotation in controlling Sclerotinia and Fusarium root rots. Three years of beans on the same ground have generally been enough to cause a serious disease problem. There are few farms on which rotation of the bean fields is not possible, yet most farmers have failed to start a rotation system at the outset. Convincing experimental evidence for the value of rotations in disease control is difficult to obtain. It is easy to demonstrate the effectiveness of rotating the bean plantings to fields which have never grown beans. But what will happen when the cycle has to be repeated remains to be seen, Some benefit from a decrease in “disease potential" can reasonably be expected but its magnitude can hardly be predicted. Even carefully controlled rotation experiments would yield only partial answers because of the endless possibilities of crop combinations, sequences, and time factors. Irrigation by sprinklers has been found to favor the spread of the bacterial diseases, and only case of bean rust so far seen in the area was in a sprinkled field. In years of average rain- fall none of the bacterial diseases has been found in furrow-irrigated beans. Where beans are to be grown under sprinklers disease-free seed will be of greater importance than where the crop is to be furrow-irrigated. Similarly, seed producing fields that are furrow-irrigated should be easier to keep free from these diseases than sprinkled fields where late pod infections are likely to occur. Even though economic damage from bean blights under sprinklers has been rare so far, there have been several border-line situations. A slight shift in the weather at a critical time might be enough to bring about a serious blight problem. Adapted disease-resistant varieties remain among the best of disease control measures. In the case of field beans such varieties are available only against curly-top, one strain of common mosaic, and halo blight. Any new variety for this area must have curly-top resistance and prefer- ably resistance to the known strains of common mosaic. These restrictions will complicate breed: ing programs for resistance to other diseases. Ce cc wi a m ot ow di al D II n much ction ay be ommon ed in spring in new- ars of ss wide- 7-top- bean in- 2 case | be in- The ground ay could ease con iemon- irs of . There failed to which to be its yield and and rain- are to crop ild be likely > so far, time es. In »mmon d prefer- te breed Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 47 Summary In the five years since commercial bean production began on newly irrigated lands in the Columbia Basin area of Central Washington, many of the important bean diseases have be- come established. The list of diseases includes Fusarium root rot, Sclerotinia root rot, Rhizoctonia, Pythium wilt, common bacterial blight, halo blight, bacterial wilt, rust, Botrytis rot, yellow bean mosaic, a strain of common bean mosaic, and curly top. The importance of these diseases and their probable origin is discussed. Many of them have ' most probably been introduced in or with the seed, some have transferred from other crops, and others may be native soil-inhabiting pathogens. The use of sprinkler irrigation has been found to favor the spread of the bacterial diseases, which are normally absent in furrow-irrigated fields. It is suggested that fields for seed pro- duction be furrow-irrigated. Experience with this new crop on new land emphasizes the importance of disease-free seed and the need for a system of rotation started before the land is generally contaminated. DIVISION OF SOIL MANAGEMENT AND IRRIGATION, U. S. DEPARTMENT OF AGRICULTURE, IRRIGATION EXPERIMENT STATION, PROSSER, WASHINGTON n il- ntro- ve it bac- m, all were sly un- rom 48 Vol, 36, No, 2--PLANT DISEASE REPORTER--Feb. 15, 1952 EVIDENCE ON THE SIGNIFICANCE OF CUCUMBER MOSAIC AND TOBACCO RINGSPOT VIRUSES IN GLADIOLUS Philip Brierley! A number of diseases apparently of virus etiology are known in gladiolus, but causal viruses have been determined for few of these. The mild mosaic of gladiolus described by Smith and Brierley (5) is known (3) to be caused by bean yellow mosaic virus, which was first isolated from gladiolus by McWhorter et al. (4). This virus is common in gladiolus, producing the familiar angular light and dark green mottling in leaves and a "pencil stripe" flower break, which in most varieties does not detract seriously from the attractiveness of the flower, The more damaging white break disease (3) spreads in the field, but the causal agent and its vector are unknown, Other diseases characterized by stunting, by ring markings or by white to brown streaking in leaves are undetermined. Therefore, when Berkeley (1) and Bridgmon (2) simultaneously re- ported isolation of cucumber mosaic and tobacco ringspot viruses from gladiolus, it became of interest to determine whether either of these viruses might be responsible for production of some of the unexplained symptoms in gladiolus. This paper reports isolation of cucumber mosaic vir- us (Cuc), tobacco ringspot virus (TRsp) or bean yellow mosaic virus (BYM) from greenhouse grown gladiolus of several varieties received from several States and with several different symptoms, and the effect of Cuc and TRsp on a seedling test variety. Isolations Three series of index inoculations from gladiolus to tobacco (Nicotiana tabacum L, var. Sam- sun), snapdragon (Antirrhinum majus L. var. Cheriot Maid Supreme), and bean (Phaseolus vul- garis L, var. Topcrop) were made on April 6, May 3, and July 6, 1951. Three to 10 plants, usu- ally five, of each test species were inoculated in each trial by dusting with carborundum and then wiping with cloth saturated with the sap of the gladiolus under test. In the first series gladiolus source plants were 60 to 80 cm. tall; in the second plants of the same group were approaching bloom; in the third plants of a different group ranged from 20 to 90 cm., chiefly 45 to 65 cm., in height. The younger, basal portions of growing gladiolus leaves furnished the inoculum. Of 14 gladiolus plants indexed in April, four yielded TRsp, three BYM, and seven no virus. In May, of eight plants of the same group, then approaching flowering, five yielded TRsp, three BYM, two of these yielding both viruses, and two plants no virus, Of 12 plants of a different group indexed in July, five yielded TRsp, six Cuc, two BYM, and two no virus. All three viruses were recovered from one of these plants, TRsp and BYM from two plants, and Cuc and BYM from one plant. Tobacco ringspot virus’ was isolated from seven varieties (Elizabeth the Queen, Greta Garbo, High Finance, Lady Luck, Picardy, Red Lightning, and an unidentified sort) from California, Florida, Indiana, or New Jersey. Cucumber mosaic virus was recovered from six varieties (Casablanca, Cover Girl, Genghis Khan, High Finance, Martha Deane, and Susannah) from Florida or New Jersey. Bean yellow mosaic virus was isolated from six varieties (Frei- schutz, High Finance, Ivy Robertson, Maid of Orleans, Martha Deane, and Picardy) from Flori- da, Indiana, New Jersey, or Ohio. In view of the free interstate movement of gladiolus, no par- ticular importance can be attached te the state of origin of a collection, but all three viruses seem widely distributed in gladiolus. The gladiolus source plants that yielded TRsp showed no uniformity of symptoms, but ex- pressed white break, stunt, or white streaking. Plants that yielded Cuc all showed white streak- ing in leaves, but other plants with similar leaf symptoms failec to yield Cuc. Gladiolus that yielded BYM expressed mottling, but this virus was not demonstrated in others that showed simi- lar mottling. The index procedure used seemed inefficient in detecting BYM, especially in the presence of TRsp, which induced necrosis of the shoot tip and leaf fall in beans. Detection cf TRsp and Cuc was more efficient, as judged by the ease with which these viruses were recovered from inocula- ted gladiolus. Snapdragons and beans sometimes detected TRsp when tobacco failed to do so. All isolations of TRsp were closely similar. Isolations of Cuc showed minor differences, only one isolate infecting snapdragon and none infecting bean. The-Cuc strain isolated from Casablanca gladiolus protected zinnia (Z. elegans Jacq. var. Golden Gem) against reinfection by Price's tester strain of this virus. The TRsp isolate protected tobacco against reinfection by the type strain of this virus supplied by H. H. McKinney. =e. Senior pathologist, Bureau of Plant Industry, Soils, and Agricultural Engineering, United States Department of Agriculture, Beltsville, Maryland. fe) b s tl b 1 fi ss Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 49 Inoculations Tobacco ringspot virus was established in young plants of cucumber (Cucumis sativus L. var. A&C), bean, snapdragon, and tobacco. On June 18, when all of these source plants were expressing well-defined symptoms, inoculations were made from each to 10 plants of one gladiolus seedling clon (G8) and to three plants of another (G5). Both seedling clons had been produced and increased in a greenhouse and were virus free when inoculated. The gladi- olus were 9 to 20 cm. tall when inoculated with TRsp by wiping all exposed leaf surface, pre- viously dusted with carborundum. On July 6 subinoculations were made from each of the eight sets of inoculated gladiolus to beans, snapdragons, and tobacco, At the time of subinoculation these plants were 50 to 65 cm. tall and the inoculum was taken from the lower half of the young- est leaf on each plant, tissue that had developed after the original inoculation was made. To- bacco ringspot was recovered from six of the eight sets of seedlings inoculated. Thirty-three of the 48 plants flowered without producing symptoms in leaves or blooms, and the remaining 15 plants had normal leaves but failed to flower. Tobacco ringspot virus isolated from gladi- olus in this series of experiments caused no symptoms in two gladiolus seedling varieties in a full season of growth. On September 4 Cuc isolated from Casablanca, Cover Girl, and Susannah, and TXsp reiso- lated from gladiolus in the experiment just described were each inoculated from cucumber to five plants of the gladiolus seedling G8 and five plants of the variety Picardy. The seedlings were 30 to 45 cm. tall and were inoculated in the soft base of the fourth leaf; Picardy gladiolus were 15 to 35 cm. tall and were inoculated in the firmer basal leaves. After 20 days yellow- ish flecks and gray lines appeared in young leaves of three of five plants of the seedling varie- ty G8 inoculated with Cuc from Casablanca. These leaf symptoms persisted and became well defined but never as prominent as the white streaking shown in many of the gladiolus plants in- dexed. On flowering November 20 to 28, the same three plants expressed conspicuous flower breaks (Fig. 1) with heavy grayish streaks extending outward from the base of the petal, visi- ble from both surfaces, and depressing development and keeping quality of the bloom. The Cuc strains from Cover Girl and Susannah failed to cause symptoms and could not be reiso- lated from the inoculated gladiolus. TRsp was readily reisolated from the seedling variety FIGURE 1. Symptoms of» cucumber mosaic in flower of gladiolus seedling clon G8, with a normal flower of the same clon, Photograph by Mead. “uses d from ar most ing in e- of some e -Sam- vul- usu- then oOlus ng rus. t iruses : six = “NG ei- par- j reak- ) Cuc cula- ». All one inca as j 50 Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb. 15, 1952 and less readily from Picardy, but it caused no symptoms that could be detected in either. Cuc derived from Casablanca was recovered with difficulty from Picardy, but no symptoms were detected in this variety. Discussion Cucumber mosaic virus was apparently first reported in gladiolus by White (8) and Wade (7) in Tasmania. These writers considered this the only virus present in gladiolus in that country and stated that it caused a pale green mottling in leaves with brown streaks in se- vere cases and pale or even white streaks in the flowers. K. M. Smith (6) listed gladiolus among plants frequently infected by Cuc in England and mentioned white or pale flecking and pencilling in flowers as characeristic symptoms. Berkeley (1) and Bridgmon (2) were the first to detect TRsp in gladiolus. These workers presented no information on the role of TRsp or Cuc in symptom expression in gladiolus. In the experiments reported here, Cuc induced white necrotic streaks in flowers and white to yellowish streaking in leaves of the test seedling clon G8, but TRsp was carried without symptoms by this clon. Symptoms produced experimentally by BYM and those of white break expressed in plants exposed to natural infection in the field clearly differ from those caused by Cuc in this clon. It seems likely that Cuc may be responsi- ble for at least some of the white streaking seen in gladiolus leaves and for some of the more damaging flower breaks. Although TRsp did not cause symptoms in clon G8, it may of course cause them in other gladiolus varieties. The occurrence of BYM, Cuc, and TRsp together in the variety High Finance without marked stunting or crippling of the flower indicates that these viruses have no primary causal relation to the more damaging unidentified diseases of gladi- olus. Gladiolus is an important reservoir of all three viruses as indicated by Bridgmon (2). Literature Cited 1. Berkeley, G. H. Gladiolus viruses. Phytopath. 41: 3-4. 1951. (Abstract) 2. Bridgmon, G. H. Gladiolus asa virus reservoir, Phytopath. 41: 5. 1951. (Abstract) 3. Brierley, Philip, and Floyd F, Smith. Carnation and gladiolus virus diseases pose serious problems. Florists' Review 99 (2567): 31-33, 1947, 4. McWhorter, F. P., Lytton Boyle, and B. F. Dana. Production of yellow bean mosaic in beans by virus from mottled gladiolus. Science 105: 177-178. 1947. 5. Smith, Floyd F. and Philip Brierley. Preliminary report on some mosaic diseases of iridaceous plants. Phytopath, 34: 593-598, 1944, 6. Smith, Kenneth M. Viruses and virus diseases. Jour. Royal Hort. Soc. 74: 482-491, 521-528. 1949. 7. Wade, G. C. Gladiolus diseases. Tasmanian Jour, Agric. 19: 36-40. 1948. 8. White, N. H. Plant disease survey of Tasmania for the three-year period, 1943, 1944, 1945, 30 pp. Tasmanian Dept. of Agric, 1946 (?) Mimeographed. (Cited by Wade). DIVISION OF ORNAMENTAL PLANT CROPS AND DISEASES we we the we er (1) Ge st th ag ch sy er D h t) e). Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 51 OBSERVATIONS OF VERTICILLIUM WILT OF GERANIUM IN OREGON C. Torgeson In August, 1950, diseased geranium plants (Pelargonium hortorum) with wilt symptoms were received from a home planting at Hillsboro, Oregon. Many of the leaves on the plants were wilted and a number of them were withered and dried. There was no discoloration of the vascular area. Isolations from the plants yielded a species of Verticillium. The isolates were determined to be Verticillium albo-atrum Reinke and Berthold, as the species is consid- ered by Rudolph (3). Verticillium has been reported as occurring on geranium in California (1) and New York (2), but has not previously been reported on this particular plant in Oregon. The pathogenicity of three of the isolates from geranium was tested in the greenhouse, Geranium plants of the Meteor variety were inoculated by making an incision at the base of the stem, placing a bit of inoculum growing on potato-dextrose-agar in the incision, and wrapping the wound with a cheesecloth strip. The check plants received only sterile potato-dextrose- agar. Lots of five plants were inoculated with the different isolates and five others served as check plants. Two weeks after inoculation several of the inoculated plants had developed wilt symptoms and within four weeks all of them showed wilt sumptoms. Verticillium was recov- ered from all fifteen of the inoculated plants. Isolates of V. albo-atrum from raspberry and peppermint were also found to be pathogenic to geranium. The peppermint isolate appeared to be more virulent than those from geranium. Literature Cited 1. Baker, K. F., W. C. Snyder, and H. N. Nansen. Some hosts of_Verticillium in Cali- fornia. Plant Dis. Reptr. 24: 424-425. 1940. 2. Dimock, A. W. Importance of Verticillium as a pathogen of ornamental plants. Phy- topathology 30: 1054-1055. 1940. 3. Rudolph, B. A. Verticillium hadromycosis. Hilgardia 5: 201-351. 1931. DEPARTMENT OF BOTANY AND PLANT PATHOLOGY, OREGON AGRICULTURAL EXPERI- MENT STATION, CORVALLIS, OREGON st A i- 4, 52 Vol. 36, No. 2 --PLANT DISEASE REPORTER--Feb, 15, 1952 POWDERY MILDEW OF KENAF IN FLORIDA William W. Diehl There are a few reports of powdery mildews attacking kenaf (Hibiscus cannabinus L.) in Asia and Africa, but there appear to be no records of their presence on this valuable fi- ber plant in the United States. Since these parasites reduce the yield of any crop, the recent finding of mildewed kenaf leaves at Belle Glade, Florida (November 17) by Warren N. Ston- er suggests a new hazard in the production of kenaf in the United States. The potential im- portance of this finding warrants special effort to determine its technical identity although only the conidial (oidial) stage of the fungus is present in the specimen. Ordinarily powdery mildews lacking the cleistothecial stage present almost insuper- able taxonomic difficulties. In this case, however, the conidia and mycelium are distinc- tive. Except for species of the genera Phyllactinia and Leveillula the powdery mildews are characterized by mycelium that does not penetrate the leaf tissues deeper than the epidermis. Since in the specimen under consideration the mycelium is found ramifying in the mesophyll, the fungus belongs to a species of one of these two genera; and since the conidia are character- istic of Leveillula rather than Phyllactinia its generic position is definite. The measurements of the conidia and the peculiar roughness of the epispore compare favorably with those re- ported by J. A. Stevenson (Plant Dis Reptr. 29 (no. 8): 214-215) for L. taurica (Lev.) Arn. as found on mesquite in the United States and agrees also with those described by N. G. Zap- rometov (Uzbekistan Exp. Sta. for Plant Protect. Publ. no. 11: p. 14, 1928) for his L. tau- rica forma hibisci found on Hibiscus trionum L.in Tashkent in Central Asia. Later, however, Zaprometov (Za Novae Volokno [= Journal concerning new fiber plants, Moscow ] 2 (no. 8/9): p. 62, 1931) discussed his "forma hibisci' as a pathogen of considerable importance on ken- af in Tashkent. Whether this "forma" is restricted to Hibiscus and is an introduction or is ubiquitous and long established on other hosts in Florida cannot, of course, be determined except by further evidence including experimental infection studies. DIVISION OF MYCOLOGY AND DISEASE SURVEY h g fe t a s Ol 7 (1 1 (: it is s Pp s d 1 c s i h Vol, 36, No, 2--PLANT DISEASE REPORTER--Feb, 15, 1952 53 ROOT ROT OF COTTON CAUSED BY THIELAVIOPSIS BASICOLA DISCOVERED IN THE UPPER RIO GRANDE VALLEY OF TEXAS Philip J. Leyendecker, Jr. Thielaviopsis basicola (Berk. & Br.) Ferraris was isolated from Pima 32 cotton collected on August 27, 1951, in two different fields located about five miles south of Canutillo, Texas. This pathogen was first reported on cotton under field conditions in 1939 by King and Barker (1) in Arizona. A detailed study (2) of the disease on cotton by King and Presley followed in 1942. No further report has been made of the disease on cotton in the United States, but Bazan (3) discovered it on cotton in Peru in 1949, This is a report, therefore, of the second field occurrence of the disease in the Southwest. The occurrence of the disease in this area extends its knowr range some 200 miles east and lends further evidence to the thesis that the pathogen is indigenous to the soils of the arid Southwest. Plants in the infested areas exhibited the droughty, sudden, leaf-collapse symptoms de- scribed by King and Presley. The author is in full accord with their observations that the above-ground symptoms may be easily mistaken for Phymatotrichum root rot. However, the typical cortical collapse of cotton root rot is not found on the roots infected by Thielaviopsis. Only a small number of the infected plants showed the typical swollen crown and extensive purple-brown vascular discoloration, It was more common to find plants which exhibited a scattered browning or purpling of the central root cylinder. Regardless of the extent of root discoloration, the above-ground portions exhibited severe wilting and subsequently died. In one field, the typical above-ground symptoms extended over an area of approximately 11/2 acres. In some rows, as many as 15 or 20 consecutive plants exhibited extreme above- ground symptoms. Thielaviopsis root rot was first noted following an irrigation in which ex- cess water had accumulated and drained very slowly. Following the death of the above-ground stem, numerous plants produced new basal shoots. No mention was made of plant recovery in the field observations in Arizona, but regrowth of infected plants was recorded in the green- house tests. As the soil dried out in these fields, certain environmental changes could occur which would depress the activity of the fungus and stimulate regrowth of the host. The second field was about one mile from the first one, and the infested spot here was one- half acre in size. Disease symptoms were identical in both fields. Short staple cotton had been grown in each field for five preceding years. Pima 32, a long staple cotton, was the first crop of this variety to be grown on these fields. King and Presley reported that the American Egyp- tian varieties are more susceptible than the Upland varieties and this probably accounts for the appearance of the disease in these fields. With the contemplated increase in acreage of long staple cotton in this region, additional reports of Thielaviopsis root rot may be expected. Literature Cited 1. King, C. J. and Barker, H. D. An internal collar rot on cotton. Phytopath. 29: 751. 1939, 2. and Presley, J. T. A root-rot of cotton caused by Thielaviopsis basi- cola. Phytopath. 32: 752-761. 1942. 3. Bazan, C. de Segura. Podredumbre radicular del algodoner. Centro Nacional de In- vestigation y Experimentacion Agricola. (Lima, Peru). Bul. 37. 1949, DEPARTMENT OF BIOLOGY, NEW MEXICO AGRICULTURAL EXPERIMENT STATION, STATE COLLEGE Ss. er- nts ad or, nd or i 4 54 Vol, 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 INFECTION OF TOMATO BY HETERODERA FROM TOBACCO SOIL A. L. Taylor On September 11, 1951, a tobacco root and a small quantity of soil were received from Dr. B. F. Lownsbery of the Connecticut Agricultural Experiment Station, these having been collected in a tobacco field near Hazardville, Connecticut, which has been planted to tobacco each year for the past ten years. On the roots of the tobacco plant and in the soil were found a considerable number of cysts of a nematode of the genus Heterodera Schmidt, 1871. The soil and cysts washed from it were used to inoculate sterilized potting soil. Tobacco and toma- to plants and pieces of potato tuber were planted on September 12. On October 3, white female nematodes of the genus Heterodera were found on the roots of the tobacco plants and numerous males of this genus found in the soil in which the tobacco grew. On November 9, similar fe- males and males were found on the roots of the tomato plants and in the tomato soil. Some of these females contained eggs in various stages of development, including eggs with second stage larvae. At the same time, brown cysts were found on the tobacco roots. The first planting of potatoes failed to grow and were replanted on October 1. Potato roots have been examined at intervals since that date, but no sign of infection by Heterodera was found as late as January 2. Cysts from the soil received from Connecticut were placed in leachings from a potato plant and other cysts placed in distilled water at the same time. Ten cysts were used in each group, being selected at random from the same lot of material. Ten days later, 785 larvae had emerged from the ten cysts in potato root leachings, while only 12 had emerged from the cysts placed in distilled water. The females, males, cysts, larvae and eggs of the nematodes found in the original material, in the pots and on the roots of the test plants have been carefully examined and compared with specimens of the golden nematode of potatoes (Heterodera rostochiensis Wollenweber, 1923) from Long Island, New York, and from other parts of the world. No morphological differences have been found which would indicate that the Heterodera from tobacco is not this species, even though it has not previously been reported as a parasite of tobacco. Tomato has long been known as a host of H. rostochiensis. DIVISION OF NEMATOLOGY INVESTIGATIONS soctlo Sm B s b ti g te B B B B Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb, 15, 1952 55 BALANSIA AND THE BALANSIAE IN AMERICA ADDITIONS AND CORRECTIONS William W. Diehl Since the publication of Agriculture Monograph no, 4 (Diehl, W. W. Balansia and the Balansiae in America. pp. 82 ill. Dec. 1950) I have been enabled to examine additional specimens of American Balansiae, especially those to be found in certain Europena herbaria, thus permitting someamplification of the record, Although most of these specimens were given but a cursory examination owing to the limited time then available, the species are so dis- tinctive macroscopically that the determinations for these additions to the record may be re- 5 garded as adequate; they do not, however, include reference to the many duplicates of previous- ly (loc. cit.) cited specimens which are fairly frequent in European herbaria. The corrections here noted are for errors thus far noted; where additional errata are de- tected I shall be grateful if they are brought to my attention. ; The recent publication by R. E. D. Baker and W. T. Dale (Fungi of Trinidad and Tobago. Mycological Papers, Kew no. 33: pp. 123, ill. 1951) includes observations on host identities hase that are especially valuable in clarifying certain hitherto significant but doubtful records. An account by A. Chaves Batista (Un pugilo de fungos -- Bol. Sec. de Agr., Industria e Comercio 16 (no. 3 e 4): 203-211, (1949) 1950) describes (pp. 204-205, f. 6-10) a new species, Dothi- me chloe insidiosa, found at Recife in Brazil on Scleria bracteata, type -- A. C. Batista no. 945; * - this would appear from the illustrations to be similar to the Venezuelan specimens cited by ng Diehl (1950) as Balansia cyperacearum, but distinguished from them by the small, discoid stro- - mata, paralleling the condition characterestic of the graminicolous B. strangulans f, discoidea. » ADDITIONS = The herbaria where the particular specimens are to be found are cited as follows: B_ -- Herbier Barbey-Boissier, Universite de Genéve, Switzerland. _— Br -- The Herbarium, British Museum, London, G -- Herbiers, Conservatoire et Jardin Botanique, Geneve, Switzerland. IK -- Herbarium, the Commonwealth Mycological Institute, Kew, Surrey, England. K -- Herbarium, Royal Botanic Gardens, Kew, Surrey, England. P -- Herbier Cryptogamique, Musée d'Histoire Naturelle, Paris, France. S -- Herbarium, Riksmuseet, Stockholm, Sweden, W -- Mycological Collections, Plant Industry Station, Beltsville, Maryland, U. S. A. BALANSIA CLAVICEPS on Setaria poiretiana (Schult.) Kunth -- Piraya, Paraguay 1879 -- Balansa extype (G, K, P, ) (This host determination by C. E. Hubbard is attested by a notation in the specimen at Kew (K). Coupled with the recent observations of Baker and Dale (loc. cit.) this fur- nishes a most satisfactory solution to the question of the correct identification of the host for the types of Spegazzini's and Massee's species. ); Trinidad 1949 R. E. D. Baker no. 17936 (IK), M. A. Brett (IK). on Gramineae indet. -- Chile, type of Claviceps philippii Rehm in herb. Rehm (S): Mexico 1865-6 M. Bougereau no. 2644 (P). BALANSIA PALLIDA Parts of the type in Rab. Fungi Europaei no, 3549 (B, Br, K, L,S). BALANSIA STRANGULANS on Panicum zizanioides H. B. K, (Ina part of the type at Kew the host is so determined by C. E. Hubbard) (K, P). This agrees with the findings in Trinidad by Baker and Dale (loc. cit). on_P. sp. 1884 Balansa Pl. du Paraguay no, 4337 (P); Brazil 1890 E. Ule no. 1334 (S), no. 2482 (S). BALANSIA STRANGULANS f. DISCOIDEA on Chloris sp. Brazil 1903 E. Ule (S). on Lasiacis divaricata (L.) Hitch. Sado Francisco, Brazil 1885 E. Ule no. 426 (S). 56 Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb, 15, 1952 BALANSIA HENNINGSIANA on Gramineae indet. Balansa Pl. du Paraguay no. 432 (P); Santa Catharina, Brazil 1884 E. Ule (S). BALANSIA CYPERACEARUM on Cyperaceae indet. Brazil 1897 E. Ule no. 2480 (S). BALANSIA AMBIENS on Olyra micrantha H. B. K, Itajahy, Brazil 1886 E, Ule no. 1198 (S); Apiahy, Brazil 1888 E, Ule no. 127-B (S). BALANSIA LINEARIS on Chusquea sp. Brazil 1894 E. Ule no. 2105 (S). ATKINSONELLA HYPOXYLON on Gramineae indet. Nova Scotia 1883 J. Macoun (K); Serra Geral, Brazil 1891 E. Ule -- as Balansia discoidea (S); Rio Ouro Preto, Brazil 1892 (E. Ule ?) no. 856 (S). ATKINSONELLA HYPOXYLON v. TEXENSIS on Stipa leucotricha Trin. Texas 1906 W. H. Long no, 54 (S); (New Mexico ?) 1950 M. P, Mauldin (W). BALANSIOPSIS GADUAE on Bambuseae indet. Santa Catharina, Brazil A. Mdéller ( -- possibly part of type of Ophiodothis gaduae Rehm) (S). BALANSIOPSIS ASCLEROTIACA on Orthoclada laxa (L. Rich.) Beauv. Peru 1911 E. Ule no. 3139 (S). CORRECTIONS p. 35. sub "I, pallens Munro 1916 F. L. Stevens" change to "1913". p. 55., sub "Guadua sp!" change "Porto Bello" to Campo Bello". p. 65. Table 2 -- eliminate "Epichloé typhina''. (Despite various published intimations that E, typhina may be seed-borne no definite proof of it appears to be forthcoming, hence this phase of Table 2 is erroneous as has been very kindly brought to my attention in a recent communication by Dr. J. H. Western.) p. 79. After "Olyra micrantha H. B. K.;.. . B. linearis" add "B, ambiens". Plate 4, fig. D. -- Change "X 6.5" to "X 2", a Plate 8, fig. E. -- Change "B. hemicrypta" to "B. ambiens", DIVISION OF MYCOLOGY AND DISEASE SURVEY tr dc 8 cc m fo to lis th fr cc m pl cc th (F It ay ay pc nu T: fe of 1ence Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb. 15, 1952 57 RODENT REPELLENT STUDIES WITH "ARASAN"-TREATED SEED CORN Jack F., Welch and Millard Graham During the summer of 1951 studies were undertaken to determine the degree of rodent pro- tection afforded seed by Arasan (tetramethyl thiuram disulfide) when applied in varying concen- trations. Observations reported from the field and tests conducted in this laboratory had indi- cated repellent action when this material was used as a seed disinfectant but no information was available as to the extent of protection resulting from specific rates of application. For the tests seed corn treated with different rates of Arasan SF! based on the normal dosage of 1/2 ounce per bushel (56 pounds) was prepared by the DuPont Company. Identification of these follows: Sample No. 1 -- Untreated corn Sample No, 2 -- Five times normal (2-1/2 ounces per bushel) Sample No, 3 -- Ten times normal (5 ounces per bushel) Sample No. 4 -- Twenty times normal (10 ounces per bushel) Sample No. 5 -- Forty times normal (20 ounces per bushel) The Arasan was stuck on the seed with a 5% methocel sticker. The quantity necessary was 3 percent by weight of the corn for samples Nos. 2 to 4, and 5 percent by weight for the highest concentration. Application was made by first applying the sticker and then the Arasan. Laboratory Tests Preliminary evaluation of the seed was carried out in the laboratory on captive white-footed mice (Peromyscus). This was accomplished by presenting individually caged animals 10 kernels of treated and untreated corn daily fora 4-day period,the consumption of each being recorded at 24-hour intervals. Five animals were used at each level of treatment. During the test no other food was given. The results of these tests are given in Table 1. Efforts were also made to appraise these seeds on meadow mice (Microtus). This test had to be abandoned, however, because of losses, due to unknown causes, among the animals. The limited information obtained indicated the treatments were of the same order of repellency to these animals as they were to Peromyscus. Fortunately the meadow mouse does not venture far from cover and for this reason is less of a factor in field depredations than are other mice. Simulated Field Tests Appraisal of the repellent action of these treated seeds when planted was carried out under controlled conditions with a known number of mice. For the test 50 kernels of corn of each treat- ment were planted in individual flats in systematic order to facilitate record keeping. Before placing the newly planted flats in the enclosure the desired number of mice were allowed to be- come established. During this period the animals were given mixed grain including corn, When the test began grain was made accessible but it contained no corn, In the first test carried out a mixed colony of animals consisting of 30 white-footed mice (Peromyscus), 10 meadow mice (Microtus), and 10 harvest mice (Reithrodontomys) were used. It soon became apparent, however, that this number of animals was too large and varied for best appraisal of the treated seed. Therefore, a second test was run in which conditions more nearly approximated those found in the field. In this test 10 white-footed mice (Peromyscus) were used. In both tests daily observations were made and the fate of each seed recorded as nearly as possible. In the test the effectiveness of the repellent treatment was measured in terms of the number of seeds which sprouted and were undamaged. The results of the two tests are given in Table 2. 'This isa 75% tetramethyl] thiuramdisulfide product formulated as a wettable powder. It is to be dif- ferentiated from Arasan Seed Disinfectant, which is a 50% non-wettable product used in dust treatment ofseeds, In this paper wherever Arasan is mentioned it has reference to the Arasan SF product, 58 Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 Table 1. Acceptance of Arasan-treated and untreated seed corn by caged white-footed mice (Peromyscus). tic Number seeds taken tir Average each day Total 4- sh : : Type : (5 animals) : day period At Sample _: Concentration : bait* : 1 : 2: 3 : 4 : (average) te: th 2 Arasan T 8+ 7 5+ 5+ 24+ ta: 5 times U 9+ 10 10 10 39+ normal th se 3 Arasan T 7+ 6+ 5+ 6+ 25+ we 10 times U 10 10 10 10 40 pe normal on of 4 Arasan a 3+ i+ 1+ 1 8+ wh 20 times U 10 10 10 10 40 normal Arasan 8+ 2+ 1+ 1+ 13+ 40 times U 9+ 7+ 8+ 8+ 33+ a normal * T denotes treated ‘ U denotes untreated ** Repellent film flaked badly Ps Table 2. Appraisal of the repellency of Arasan treated seed corn to captive mice under ? simulated field conditions. be ; Fate of 50 seeds planted in each flat during 15-day test period* 1% : : : : : : Percent : seed : 3 : : : Number : sprouted g : : Number: Number : Percent : Number : sprouts : and un- F Flat No, : Treatment : taken: Uncovered : Disturbed : sprouted : cut : damaged Test 1** 1 Untreated 25 12 74 23 19 8 be 2 Arasan21/20z. 40 3 86 7 7 0 per bushel 3 Arasan5o0z. per 22 11 66 22 11 22 ; bushel vie 4Arasan 10 per 32 3 70 16 7 18 bushel 5 Arasan 20 oz. per 23 10 66 22 4 a ae bushel wi Test 2*** 1 Untreated 20 1 42 19 7 24 2 Arasan 2 1/2 oz. 31 0 62 14 2 24 tiv per bushel pli 3 Arasan 5 oz. per 7 1 16 38 2 72 the bushel for 4 Arasan 10 0z. per 10 0 20 40 2 76 bushel 5 Arasan 200z. per 5 0 10 45 0 90 WI bushel MI * In some flats individual seeds were neither distributed nor didthey germinate, These are not accounted for in this tabulation. **x In this test seeds were exposed to a mixed colony of animals consisting of 30 white-footed mice (Peromyscus), 10 meadow mice (Microtus), and 10 harvest mice (Reithrodontomys). *** In this test seeds were exposed to 10 white-footed mice (Peromyscus). ed s). Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 59 Discussion As shown in Tables 1 and 2,seed corn treated with Arasan was afforded considerable protec- tion from depredations by mice in tests carried out in the laboratory and in enclosures simula- ting field conditions. In the laboratory test (Table 1), caged white-footed mice (Peromyscus) showed greatest aversion to seed treated at the rate of 10 ounces of Arasan per bushel of corn, At the higher concentration (20 ounces per bushel) the repellent coating had a tendency to shat- ter off which undoubtedly contributed to the lower repellency of this sample of treated corn. At the two lower concentrations (2 1/2 and 5 ounces per bushel) acceptance of treated seed was re- tarded but to a lesser degree. In the tests with planted seed (Table 2) it was possible to appraise the rodent repellency of the Arasan treatments more adequately. Although little benefits resulted in the two tests with seed treated at the rate of 2 1/2 ounces per bushel, at levels above this promising protection was afforded. As shown in this table the effectiveness increased as the concentration of the re- pellent was increased. This was particularly striking in the second test (Test 2, Table 2) where only white-footed mice had access to the planted corn, At the termination of this test 90 percent i of the seed treated at the rate of 20 ounces of Arasan per bushel had sprouted and was undamaged, whereas only 24 percent of the untreated corn survived (Figure 1). FIGURE 1. Illustration show- ing the relative resistance of Ara- san treated seed corn to mouse Peromyscus) attack. Photograph taken on the eleventh day of ex- posure. Identification of flats and number of plants undamaged in each follows: U -- Untreated (2); 5X -- 2 1/2 ounces Arasan per bushel (10); 10X -- 5 ounces Ara- san per bushel (33); 20X -- 10 ounces Arasan per bushel (33); 40X -- 20 ounces Arasan per bushel (37). The results of these tests indicate relatively high concentrations of Arasan are needed to pro- vide planted seed optimum protection against mouse damage. Whether or not such concentrations would be necessary under actual field conditions is not known. This is yet to be determined. It is of interest to note, however, that in experiments conducted by the writers the 50% Arasan prod- uct when dusted on seed corn and placed in storage proved to be very effective as a repellent for wild rats and house mice in a concentration of approximately 2 ounces per bushel. With planted seeds, soil adsorption, leaching, and other processes undoubtedly exert an influence on the effec- tiveness of the material. The sticker used to bind the repellent on the seed and its method of ap- plication may also have a bearing on the activity of the compound. It is believed, however, that the results obtained in these studies are significant since the test constituted optimum conditions for rodent attacks. WILDLIFE RESEARCH LABORATORY, U. S. FISH AND WILDLIFE SERVICE, U. S. DEPART- MENT OF THE INTERIOR, DENVER FEDERAL CENTER, DENVER, COLORADO } ¥ ged re 60 Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb, 15, 1952 PASTURE AND FORAGE LEGUME AND GRASS DISEASES IN NORTH CAROLINA IN 1950 AND 1951 J. Lewis Allison, J. C. Wells and Homer D. Wells This supplements the original report which appeared in Plant Disease Reporter 34: 205. 1950, Economic damage to pasture and forage legumes and grasses was caused by the following diseases in 1950 and 1951. The causal pathogen was identified in each case, Alfalfa wilt (Corynebacterium insidiosum), first found and identified in one locality in west- ern North Carolina in 1949, was found in several additional localities in 1950 and again and more widespread in 1951. It has now been positively identified in alfalfa fields in several of the west- ern counties, Crown and stem rot (Sclerotinia trifoliorum), which was especially destructive to alfalfa and clovers (crimson, medium red, and Ladino) during the winter of 1949, was not nearly so de- structive to any of these legumes during either the winter of 1950 or that of 1951. The winter months of both years were much drier than normal, and although the disease was present in fields of all the above legumes it did not develop and spread owing to the unfavorable environ- mental conditions. Summer blight (Rhizoctonia solani) was omnipresent throughout the Piedmont and Coastal Plain regions of the State during the summer seasons of both 1950 and 1951. The normal hot, humid weather of this season favored the development and spread of Rhizoctonia foliage blight. Big trefoil, Ladino clover, alfalfa, annual lespedeza, tall fescue grass, orchard grass, and ber- muda grass were all susceptible and established stands of these legumes and grasses were fre- quently weakened and sometimes lost following severe attacks of the disease. Southern blight (Sclerotium rolfsii) was also omnipresent throughout the Piedmont and Coastal Plain region of North Carolina during the summer seasons of both 1950 and 1951. Periods of hot, humid weather favored the development of this disease. Ladino clover, annual lespedeza and alfalfa were most severely damaged. Ladino clover fields frequently had plants, in areas several feet in diameter, killed by blight. However, because of its stoloniferous habit of growth clover would grow back into these areas in the fall of the year after blight had been arrested by dry, cool weather, Leaf and stem diseases were found throughout the State and caused defoliation and stem dam- age on susceptible hosts during all months of 1950 and 1951. Of the principal legumes, alfalfa was damaged by downy mildew (Peronospora trifoliorum), leafspots (Pseudopeziza medicaginis, Pseudoplea briosiana, and Pleospora herbarum), black stem (Ascochyta imperfecta), anthracnose (Colletotrichum trifolii), and rust (Uromyces striatus); Ladino clover by the leafspots (Pseudo- monas syringae, Curvularia trifolii, Pseudoplea trifolii, and Stagonospora meliloti), leaf gall (Urophlyctis trifolii), and yellow patch virus; crimson clover by sooty blotch (Cymadothea tri- folii) and vein banding virus; and annual lespedeza by powdery mildew (Microsphaera diffusa). Of the principal grasses orchard grass was damaged by brown stripe (Scolecotrichum graminis), leafspot (Stagonospora maculata) and rust (Uromyces dactylidis); tall fescue grass by leafspot (Helminthosporium dictyoides); and bermuda grass by leafspot (Helminthosporium giganteum). Root rots (Fusarium spp.) caused depletion of established stands of alfalfa on sandy soils in the Piedmont and Coastal Plain regions of the State in 1950 and 1951. Root knot nematodes (Meloidogyne spp.) were found attacking forage legumes throughout the State during 1950 and 1951. Ladino clover was very susceptible and was frequently killed on sandy soils. Dodder (Cuscuta arvensis) was found throughout the State on annual lespedeza during 1950 and 1951 and frequently reduced forage and seed yields. Violet root rot (Rhizoctonia crocorum), heretofore unreported in North Carolina, was first found in alfalfa in one locality in the western part of the State in 1950 and in several locations in this region in 1951. Alfalfa stem nematode (Ditylenchus sp.), reported from one field in Harnett County in 1949, was not found anywhere in the State in 1950 and 1951. The original infected field was plowed un- der and it was recommended that no alfalfa be grown in that locality. Other diseases of forage legumes and grasses were found and identified during 1950 and 1951 but were cither limited in scope or were causing little damage. DIVISION OF FORAGE CROPS AND DISEASES, U. S. BUREAU OF PLANT INDUSTRY, SOILS AND AGRICULTURAL ENGINEERING, NORTH CAROLINA AGRICULTURAL EXPERIMENT STA- TION AND NORTH CAROLINA AGRICULTURAL EXTENSION SERVICE, RALEIGH to we vi al ed sc ay Ec rc le th br of | of fl be L D Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb, 15, 1952 61 BOTRYTIS ON FLOWERS OF ALFALFA, SWEETCLOVER AND RED CLOVER Fred Reuel Jones Toward the end of a long rainy and humid period in August, 1951, alfalfa flowers were noted to turn brown soon after opening and to remain adhering to the rachis. These brown flowers were soon covered with a sparse gray mould, apparently a Botrytis of the cinerea type. On vigorously growing plants, as many as 5 successive racemes were destroyed. The mould was also sometimes found on lesions at which petioles of young leaves had broken, It was not limit- ed to alfalfa, but was found on dead flowers of a few late flowering sweetclover plants, and sometimes sparsely on flowers of red clover. This mould has not been reported previously at Madison, The only report found in readily available literature of a Botrytis on alfalfa flowers and shoots is that by Hurst (2) on Prince Edward Island in 1937, However, Cormack (1) isolated and studied a Botrytis from alfalfa roots in Alberta, and R. E. Smith (3) in California obtained a Botrytis of the cinerea type from leaves of Medicago hispida incubated in a moist chamber, From the brief examination that could be made of the flowers before the moist period ended the importance of the Botrytis in destroying them was not easily judged. The petals developed brown spots soon after they were exposed, but when these were decolorized and examined there was often found at the center of the mycelium in the brown spot a spore that appeared to be either of Stemphylium botryosum, which was causing extensive spotting of young leaves at this time, or of an Alternaria. Mycelium was sometimes present in the stigma or the stamens by the time the flower was fully open. Buds without petals exposed in the damp weather appeared to develop normally. Thus it appears that in humid weather Botrytis may become the conspicuous mem- ber of a group of fungi to which petals are especially susceptible and by which flowers may be rapidly destroyed. Literature Cited 1. Cormack, M. W. Sclerotinia sativa, and related species, as root parasites of alfalfa and sweetclover in Alberta. Scientific Agriculture 26: 448-459, 1946. 2. Hurst, R. R. 16th Ann. Rept. Canadian Plant Disease Survey. pp. 14-15. 1937. 3. Smith, R. E. The life history of Sclerotinia trifoliorum with reference to the green rot of apricots. Phytopath. 21: 407-423, 1931. DEPARTMENT OF PLANT PATHOLOGY, UNIVERSITY OF WISCONSIN, MADISON 1950, st- 1ore St- and l x ber- yastal a ~ wth by lam- ‘a lo- is), t le ; in “st in 49, un- 1951 Ss 62 Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb. 15, 1952 CUCURBITARIA PITHYOPHILA, AN ENTOMOGENOUS FuNGUs! J. S. Boyce The fungus Cucurbidothis pithyophila (Fr.) Petrak described from a specimen on Pinus flexilis James from Idaho (8:198), has recently been mentioned by Davidson (3) as associated with cankered areas of small twigs of P. monticola D. Don at Nakusp, British Columbia. This is a synonym for Cucurbitaria pithyophila (Fr.) Ces. & de Not. (9) first described nearly a cen- tury ago (Comm. Soc. Critt. Ital. 1:214. 1863). Years back while investigating Cronartium ribicola Fischer on Pinus monticola in British Columbia, Cucurbitaria pithyophila was found associated with hypertrophies on P. monticola. The somewhat spindle-shaped swellings on twigs of trees of large-sapling and small-pole size in well stocked stands could, at a cursory glance, be mistaken for swellings caused by the rust fungus. However, the swellings with which C,. pithyophila was associated were usually shorter and more abrupt than those caused by Cronartium ribicola. Furthermore, close examination showed minute, black, globose and clustered perithecia seated on a gray wrinkled substratum occurring as a broad ring around twigs and small branches or as a patch on one side of larger stems, including the main stem. There was no apparent injury to the underlying cambium and sapwood, but a critical investigation was not made. Economically, Cucurbitaria pithyophila was of no consequence, generally occurring on sup- pressed twigs or small branches that would die naturally from shading. Actually the fungus de- velops on a scale insect infesting the pines, the swelling being largely composed of insect materi: al and any insignificant injury the stem suffers is attributable to the insect. The exact relation- ship between the scale insect and C. pithyophila is unknown, It may be analogous to Septobasi- dium burtii, as described by Couch (2), in which the fungus is dependent on the insect for its ex- istence, Realizing that the fungus was associated with a scale insect, a collection made at Daisy Lake (now Garibaldi). British Columbia, on Pinus monticola in October 1924 together with a letter giv- ing details was sent to the late Roland Thaxter in 1926. Following is his reply, dated April 5, 1926: "Your letter enclosing specimens of 'Sphaeria' Spraguei was duly received and should have been answered more promptly. I remember giving this name to Bethel many years ago, and I believe I was the first to recognize the fact way back in the middle eighty's that this was an entomogenous fungus. I once sent it to Cockerell who thought the scale was a new genus and was much excited about it, but I believe it has become well known and is surely European, for the same thing has been described from various parts of Europe. I wonder if the scale is really Chermes. I should be glad to know definitely. I have always intended to publish a note of this form but shall never get at itI fear. You are right in thinking that the slight distortion is due to the scale alone. Melogramma Spraguei was de- scribed first by B. and C. in Grevillea, N.A.F. No. 863, put by Saccardo in Thyridium I think, It is the same as Cucurbitaria pithyophila DeNot Sfer., Ital. 60, 1. 57. Sphaeria p. Schm. and Kunze in Fr. Syst Il, 425. I think Kauffman published a note on it in Rep. Mich, Acad. Vol. 13, p. 243, 1911. It has recently been again described as a new genus by Petrak who mistook the cocci for a fungus stroma! This is in a recent number, that is within a few years, of Annales Mycologici. Kauffman's note calls it Cucurbitaria pithyo- phila I think.’ Kauffman's note, mentioned in Thaxter's letter, merely lists Cucurbitaria pithyophila on Abies pectinata in a key for the Ascomycetes (5:243), so it apparently has no reference to the United States or Canada, where the fungus is found on a scale insect or insects occurring on the bark of three white pines. It is known from Colorado and Idaho on Pinus flexilis and from British Columbia and Washington on P, monticola. It has not been recorded on P. lambertiana Dougl. or P. albicaulis Engelm. The fungus has been reported on P. strobus at t several places in the East from New York south to Georgia. Most European accounts of C. pithyophila emphasize its pathogenicity and none mention any connection with insects, although the macroscopic illustrations of C. pithyophila var. cembraé Rehm on Abies alba (pectinata) at Vallombrosa, Italy, in the paper by Cavara, look exactly like the fungus as it appears on pines in Canada and the United States. Saplings of A. alba developed !The writer is indebted to R. W. Davidson, G. H. Hepting, and J. H. Miller for suggestions on this paper. a a I win ( | | h Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb, 15, 1952 63 a slight thickening of the wood and a marked thickening of the bark at the place of infection, accompanied by cracking, according to Cavara (1). Many trees, with stems encircled, died. In German nurseries Mehlisch (6) found that young plants of Picea excelsa, Pinus cembra, P. strobus, P. sylvestris, Abies alba, A. nobilis, and A. nordmanniana were commonly killed. Nodular swellings were produced on the branch forks of A. nobilis and A. nordmanniana, In od a 30- to 40-year old plantation of Pinus sylvestris in Scotland and ina neighbouring plantation This somewhat older, encircled branches or leaders were killed according to M'Intosh (7), whereas : ones if the fungus was confined to one side of a stem or branch, marked hypertrophy and contortion resulted and the wood became resin-soaked, but death did not follow. However, in Denmark tish the fungus was considered to be of no pathological importance by Ferdinandsen and Jorgensen “i (4:136), since the injury to infected branches of Pinus sylvestris was so slight. +a Unfortunately, never having seen this fungus in Europe, the writer is unable to reconcile pane the differing opinions as to its pathogenicity there and here, nor to explain why scale insects eter have not been recognized in connection with it there. ion nn Literature Cited oe 1, Cavara, F. Ueber eine neue Pilzkrankheit der Weisstanne, Cucurbitaria pithyophila (Kunze) De N. Ztschr, f. Pflanzenkr, 7:321-325, 1897. 1 sup- | 2. Couch, J. N. The genus Septobasidium. 1IX+480 pp. Chapel Hill: The University = ée- of North Carolina Press. 1938. materi: 3. Davidson, R. W. A western white pine twig canker, U.S. Dept. Agr. Plant Dis. Reptr. 34:99, 1950. snail 4, Ferdinandsen, C., and C. A. Jorgensen, Skovtraeernes sygdomme,. XI+571 p. —— Copenhagen: Gyldendalske Boghandel -- Nordisk Forlag. 1938-1939, 5. Kauffman, C. H. Unreported Michigan fungi for 1910, with outline keys of the common y Lake — of Basidiomycetes and Ascomycetes. Mich, Acad. Sci. Rpt. 13:215-249, 3 = 6. Mehlisch, K. Ein pilzlicher Schaddling on Abies. Blumen-u. Pflanzenbau ver. mit. Gartenwelt 42 (8):92. 1938. [Rev. Appl. Mycol. 17:493. 1938.) 7. M'Intosh, C. Cucurbitaria pithyophila, Fries. Roy. Scot. Arbor Soc. Trans. 29:209- auld 210. 1915. on 8. Petrak, F. Mykologische Notizen III, Ann. Mycol, 19:176-223. 1921. that 9. Welch, D. S. A monographic study of the genus Cucurbitaria in North America, Myco- logia 18:51-86. 1926. . I YALE UNIVERSITY, NEW HAVEN, CONNECTICUT vays de- m ‘ia Pp. 1us at is o- on the ‘om tiana laces on cembrae y like >loped paper. / 64 Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 SEX AND COMPATIBILITY IN THE OAK WILT FUNGUS 1 George H. Hepting, E. Richard Toole, and John S. Boyce, Jr. In the course of oak wilt diagnosis in the southern Applachian region, isolates of the oak wilt fungus (Chalara quercina) were obtained from 29 trees, representing infection areas in several States. To date, the mass isolate from only one tree (No. 419) has produced fertile perithecia directly, while the others produced them only when suitably paired or spermatized. All cultures were then single-spored; none of these single conidial isolates has produced fertile perithecia, indicating that this fungus, as represented by these isolates, is not homothallic. By using conidia from a given single-spore culture as male cells to spermatize other cul- tures, we have found that our isolates are not only self-sterile, but are hermaphroditic and of two types with respect to compatibility. That is, in the case of two hermaphroditic thalli of Opposite compatibility, the conidia from either one will fertilize the thallus of the other, re- sulting in fertile perithecia in as short a time as 3 days. The fungus is thus interfertile and heterothallic, as postulated by Bretz. 3 It has been demonstrated in the case of Hypomyces so- lani that no fertilization can take place between hermaphrodites or unisexual males and females if the compatibility type is the same. 4 The sex and compatibility situation in this fungus parallels that in Hypomyces solani, as demonstrated by Hansen and Snyder. 4, 5 In their case, unisexual males and females, and also neuters, occurred, in addition to the self-sterile hermaphrodites. Although our early experi- ments indicated some possibly unisexual lines in Chalara quercina, more tests with improved technique showed isolates from all 29 trees herein studied to be self-sterile hermaphrodites, that were interfertile where a given pair was composed of opposite compatibility types. This announcement is merely intended to present the sex and compatibility situation of Chalara quercina as determined by the isolates available at Asheville. The supporting data and techniques will be given in more detail in a later publication, These findings offer an explanation for the occurrence of perithecia in nature only in those trees where the fungus is complete with respect to sex and compatibility. This would be the case only when two or more thalli, with appropriate constitutions, such as two hermaphrodites of opposite compatibility, were in the tree. This has proved to be so in our tree No. 419, DIVISION OF FOREST PATHOLOGY, BUREAU OF PLANT INDUSTRY, SOILS, AND AGRI- CULTURAL ENGINEERING, U. S. DEPARTMENT OF AGRICULTURE, ASHEVILLE, NORTH CAROLINA TThe authors are most grateful to Dr. W. C. Snyder of the University of California for his invaluable counsel, in the interpretation of the results reported herein. 2Hepting, G.H., E.R. Toole, and J.S. Boyce, Jr, Perithecia produced in an unpaired isolate of Chalara quercina, and its possible significance in oak wilt control. Plant Dis, Reptr. 35:555, 1951. 3Bretz, T. W. A preliminary report on the perithecial stage of Chalara quercina Henry. PlantDis. Reptr. 35:298-299. 1951. Hansen, H.N.and W.C.Snyder. The dual phenomenon and sex in Hypomyces solanif.cucurbitae, Amer. Jour. Botany 30:419-422, 1943. Hansen, H.N., and W. C. Snyder. Inheritance of sex in fungi. Natl. Acad. Sci. Proc, 32:272-273. 1946. (A to ez vi in ge dé gl a fe oO! n al th p! eI ri da b; in bi tc tc Pp re Si a] 01 tk r tk te ir D ow lara 946, Vol, 36, No, 2--PLANT DISEASE REPORTER--Feb. 15, 1952 65 2,4-D INJURY TO COMMON HORSECHESTNUT CAUSING VIRUSLIKE SYMPTOMS F. P. Hubert, W. A. McCubbin,! and W. H. Wheeler Viruslike symptoms apparently caused by 2, 4-D on branches of the common horsechestnut (Aesculus hippocastanum L.) were first observed on May 19, 1949. This species is not known to be reported in literature as being affected by 2,4-D, and there is no record of any virus dis- ease on horsechestnut in this country. The specimens having the viruslike symptoms were submitted by George Gingras, super- visor of the U. S. Naval Observatory ground-maintenance service, for determination of the injury. The affected branches showed die-back of the terminals, spindly new shoots, and a general chlorosis in small yellow leaves which were cupped and deformed, Tip burn of a secon- dary nature was also found on the malformed leaves. Because of the possibility of a new virus disease, the writers visited the Naval Observatory grounds on June 2, 1949. Two 25- to 30-year-old horsechestnut trees were observed to be in a generally chlorotic condition with the above-named symptoms, one tree being completely af- fected and the other tree almost so except for the topmost branches and other high branches on one side of the tree. The leaf burn was found to be secondary due to prolonged hot weather. Ab- normally thickened twigs and cracks in the twig bark similar to that caused by frost injury were also noted. An examination of the branches by Mr. McCubbin showed that the wood growth in 1947 and the early part of 1948 was normal, while a pronounced growth irregularity was found in the wood produced in the late spring or early summer of 1948. Presumably at that time the twigs thick- ened and a second growth of terminal shoots began. It is believed that this new growth was not ripened in the fall and was winter-killed. Although there appears to be no literature on the effect of 2,4-D on the common horsechest- nut, the Research Report of the Sixth Annual North Central Weed Control Conference, 1949, does show that a related species was affected. The red buckeye (Aesculus pavia L.) was killed by a combination of 2, 4-D and 2, 4,5-T used by the Tennessee Valley Authority in weed control in Alabama and Tennessee, It is probably significant that more than one application of this com- bination spray was needed to kill the trees. Mr. Hubert has also been informed that F. A. Wel- ton, of the Ohio Agricultural Experiment Station, has recorded in unpublished notes a response of the common horsechestnut to 2, 4-D. Mr. Gingras stated that 2, 4-D was used on the Naval Observatory grounds-about June 1948, to kill poison ivy at a point approximately 75 yards from the horsechestnut trees. It is quite possible that some of the 2, 4-D spray was carried to the horsechestnut trees by wind drift. How- ever, it is more probable, because of the severity of their injury, that 2,4-D was applied di- rectly to the two horsechestnuts. Since the initial observations it has been established that the same mechanical sprayer used for the 2, 4-D operation was used later in the summer of 1948 in applying DDT to the horsechestnut trees for Japanese beetle control. Although orders were given to clean the sprayer and the tank after using 2,4-D, it is believed that sufficient remained or was absorbed in the 600-gallon wooden sprayer tank, so that when DDT was used later it caused the chlorotic symptoms on the two horsechestnuts and a few branches of an adjacent elm which received some of the DDT spray. In the fall of 1951, more than two years after the initial observations, the few branches of the elm tree appeared normal. The horsechestnut that was partially affected with viruslike symp- toms has entirely recovered. The completely affected tree, however, was evidently so seriously injured that it was not able to recover. DIVISION OF PLANT QUARANTINES, BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE, AGRICULTURAL RESEARCH ADMINISTRATION, WASHINGTON, D. C. lRetired January 31, 1950. | 66 Vol, 36, No, 2--PLANT DISEASE REPORTER--Feb., 15, 1952 ON THE SO-CALLED "UNKNOWN DISEASE" AND RELATED DISEASES ON COCONUT-PALMS IN THE WEST INDIES Henning P. Hansen! The so-called ''Unknown Disease" of coconuts in the West Indies has been the object of scientific investigations since 1880, when the first committee for this purpose was appointed in Cuba by''Academia de Ciencias" (4). However, no pathogen was ascertained and the disease remained unexplained. Its often spreading habit gave rise to the persistent suspicion that the disease was contagious. In recent years a virus cause has been suggested (6). Investigations by the author during 1949-51 yielded following results: (a) The disease is not infectious, but is due to a toxic condition of the specific soils. This conclusion is based on detailed studies of the symptoms and incidence of the disease, on trans- mission tests and other experiments, on historical data, and on all other collected facts. (b) A similar disease can be produced by poisoning the palms with small quantities of cer- tain substances, e.g. cadmium chloride. It was the first time that corresponding symptoms have been produced on purpose. The detailed studies by the author are described in a comprehensive report (2). In this article the apparently puzzling main features of the disease are explained. Within the regions affected by this disease the soils are derived from the so-called Mont- pelier-limestone and geologically related formations. These are deep-sea deposits of Eocene age, composed of shells of Foraminifera and Radiolaria, Their occurrence within the West Indies is mainly limited to the countries surrounding the Bartlett-Deep, the deep sea-trough west of Jamaica with depths amounting to almost 4000 fathoms, where similar deposits are still formed. Outside this region corresponding formations occur in Barbados and in parts of Trinidad and the adjoining north coast of South America (3). These countries are just those where coconuts for ages have died from unexplained, slight- ly varying diseases. Thus the so-called unknown disease in Jamica has been known to exist in the West-End since 1871 at least, and here the coincidence between the areas affected and their geologic origin has been noted previously (5). In Cuba and Haiti the same disease has been known for at least the same period of years, and it was reported from the Cayman Islands as early as 1834 -- or rather from Grand Cayman: In a report in 1889 (7) is stated that the disease did not exist in Cayman Brac, but it was serious in Grand Cayman, where: "inhabi- tants have been most persevering in their efforts to reestablish their coconut walks, but it is of no avail. A grove may do well for a time, and produce a crop of fruit, but suddenly it is attacked, the disease often first siezing the tallest and finest palms. Or again, the palms may all die off, when they are from 6 to 10 feet high without producing any fruit." In Barbados it has never been possible to grow coconuts successfully. They have died from a disease, which Fawcett (1) regarded as identical with the one in Grand Cayman, In Trinidad and British Guiana the so-called "Bronze Leaf Wilt'’ on coconuts has existed for a very long period of time. The disease in the latter countries was distinguished by Leach (5) from the one in Jamaica because of some variation in symptom development, and bronze leaf wilt is generally stationary and non-spreading. The disease in the western Caribbean, which was named the unknown disease by Leach (5), has also remained localized to certain districts, e.g. in Jamaica to the West-End, where it has persisted for at least 80 years. Within the affected districts, however, it often behaves as though spreading rapidly, giving the impression of virulent infectious spread. Nevertheless, for many reasons, summarised above as (a) and (b), it must be maintained that the disease is due to a poisoning through the soil. The spread and other puzzling features have a special reason: The intensity of the toxic condition increases, perhaps suddenly, and decreases from time to time. Increased intensity means spread of the disease. Although apparently never realised there actually exists a mechanism, likely to produce such variations, which explains the behavior of the disease clearly: namely sea-spray on the specific soils concerned. The spreading form of the disease in West Jamaica occurs within Formerly Plant Pathologist (Temporary) for the Coconut Research Scheme of Jamaica-Colonial Development & Welfare, R-21. Scientific Adviser for the Danish Ministry of Agriculture concerning plant virus diseases. Jar the in are cha roc sul anc lir me fer unk cor nut Po lea Po Ca na! dis ce] are Sal the dat | str So} sti be: int su tat fe1 Ca! on Ra se of Li ne nay ‘eS Ww Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb, 15, 1952 67 a few miles from the sea only, i.e. within reach of the sea-spray. It is an old experience in Jamaica and Grand Cayman that virulent spread of the disease appears after hurricanes, which, where they hit, carry large quantities of sea-water inward over land. Toxic substances may occur in the local sea-water, when stirred up by strong winds; or the toxins may occur in those soils derived from the specific geologic formations mentioned, in an absorbed condition from which they can be released by sea-water. The latter possibility is most probable, since a number of elements including some which are toxic to plants, actually will be released from absorption by salt water through base-ex- change. This is the well known phenomenon that is technically utilised in permutite-filters. Experience in Jamaica that the disease is less severe where the palms grow on limestone- rock than where they grow on residual soils from which the lime has leached away, appears not surprising from a chemical point of view. The still existing difference between Grand Cayman and Cayman Brac seems to be due to the same effect, because Cayman Brac is an almost bare limestone-rock island. It should be added that this limestone-rock effect does not necessarily mean that dressing of"'diseased" soil with lime will counteract the disease. However, certain fertilizers should be expected to intensify the diseased condition in the same way as sea-Salt. In any event, the spreading behavior of this non-infectious coconut-disease, the so-called unknown disease, can be accounted for by the mechanism of sea-spray on such soils, which contain toxic elements in absorbed condition, Another mechanism for a spreading type of the similar disease bronze leaf wilt on coco- nuts was observed by the author in the Pomeroon River district of British Guiana, Here the bronze leaf wilt behaved in a way very similar to the disease occurring in Jamaica, but at Pomeroon River the spread appeared to be a consequence of the periodic floods from the vast savannah swamps surrounding that district. It has already been mentioned that the bronze leaf wilt in Trinidad and British Guiana is ordinarily localised and does not spread as at Pomeroon, The symptoms are only slightly different from those of the disease in the western Caribbean countries, but it is generally accepted as a physiologic disease. However, the ordi- nary lack of spread of the disease in Trinidad and British Guiana is not a valid character of distinction, as its behavior at Pomeroon shows, It is not surprising that spread is more ex- ceptional in those countries than in the western Caribbean region, because the former countries are out of reach of most hurricanes, and because of the more local distribution of soils of the same specific geologic origin. Further investigation must decide whether the toxins producing the disease in the western Caribbean are identical with the cause of the bronze leaf wilt in Trini- dad and adjoining countries. Several reasons suggest that the toxin producing the unknown disease of coconut palms is strontium. Although related to calcium this element is known to act as a plant poison. In the soils concerned with the disease its origin would probably be Radiolarian, because it is a con- stituent of the skeletons of certain Radiolaria. The question of occurrence of strontium in the soils concerned needs further investigation before control measures for the coconut disease can be suggested, but it is a matter of great interest also for other crops than coconuts. For instance, besides a possible toxic effect on sugar-canes, reducing their growth, this element may reduce the net sugar yield by precipi- tating some of the sugar as strontium saccharate. Formation of this compound may also inter- fere with the industries based on fermentation of sugar. In consideration of the situation of replanting coconuts in Jamaica after the recent hurri- cane of August 1951, the disease can be expected to turn up wherever sea-water has been carried onto soils consisting of residue of the Montpelier-limestone formations, especially soils of Radiolarian origin. Thus the disease may turn up in new sites, where it has never been ob- served before, even in some localities of the East End of Jamaica. Here, fortunately, most of the soils are derived from other geologic formations. Literature Cited 1. Fawcett, W., 1888: Bull Bot. Dep. Jamaica, No. 6. 2. Hansen, Henning P., 1950: Report of 1950 (manuscript). 3. Hill, Robert T., 1899: Bull. Mus. Comp. Zool., Harvard College, Vol. 34. 4. Horne, W. T., 1908: Estacion Central Agron., Cuba, Bull. 15. 5. Leach, R., 1946: Tropical Agriculture 1946. 6. Martyn, E. B., 1949: Tropical Agriculture 1949, 7. Vendryes, Henry, 1889: Bull. Bot. Dep. Jamaica, No, 11. i ise ie This ns- er- 5 t= : | ght- | nds s ) f (5), has ed d 1 1ing 68 Vol. 36, No. 2--PLANT DISEASE REPORTER--Feb. 15, 1952 UNUSUAL RECORDS AND OTHER BRIEF NOTES ON PLANT DISEASES OAK WILT SURVEY IN KANSAS By Ivan J. Shields A second focus of oak wilt infection in Kansas was found two miles east of Bonner Springs, in Wyandotte County. In response to a letter referred to me by Dr. T. W. Bretz, Division of Forest Pathology, Columbia, Missouri, the site was visited November 3 and Chalara quercina was isolated from several Quercus velutina trees. Thirty to forty trees appeared to be in- volved in this area. The isolates were verified by Dr. Bretz. Although no aerial surveys were made, the eastern 35 counties, which contain the majority of the Kansas oaks, were visited during the late summer by automobile. During the past two seasons about 10 percent of the oaks have been observed. Areas not accessible by automobile were not visited. The survey was made possible by the Kansas State Entomological Commission, DEPARTMENT OF BOTANY, UNIVERSITY OF KANSAS, LAWRENCE MERCURY SPRAYS GIVE INDICATION OF REDUCING BACTERIAL LEAF SPOT OF PEACH FOLIAGE By R. S. Kirby A demonstration was conducted in York County, Pennsylvania, to determine the relative effectiveness of sulfur and mercury in preventing brown rot, blossom blight, and other diseases that might be present on peaches. Four rows in a commercial orchard received four sprays of Puratized Agricultural Spray (1 pint in 100 gallons). Dates of application were (1) pink on April 17; (2) full bloom on April 27; (3) petal fall on May 3; and (4) first cover on May 23. The second cover and later sprays were wettable sulfur. The adjoining rows were sprayed throughout the season with wettable sulfur. An outbreak of bacterial leaf spot (Xanthomonas pruni) developed late in the summer. On August 31 the amount of bacterial leaf spot and brown rot (Monilinia fructicola) was determined, Percentage leaves infected with bacterial leaf spot Variety : Mercury sprayed trees : Sulfur sprayed trees Rio Oso Gem 5. 15. Hale tr. 30. Mixed Elberta and Hale 2. 5. Average 2.3 16.6 Under conditions of this trial, mercury sprays markedly reduced bacterial leaf spot. The trials should be continued to obtain further information, The only foliage injury observed occurred on the variety Cumberland; the injury showed up only after the fourth mercury spray was applied and the trees were about normal by harvest. On August 31 the foliage on Rio Oso Gem, Hale and Elberta was in better condition where mercury had been applied than where sulfur was used throughout the season. There was less brown rot blossom blight and fruit rot in the rows receiving mercury than in those only receiving wettable sulfur. PENNSYLVANIA STATE COLLEGE, STATE COLLEGE TOMATO SPOTTED WILT IN MARYLAND By John J. Smoot One Marglobe tomato plant, infected with the spotted wilt virus, was found in the author's home garden in Frederick, Maryland, The source of infection was not determined, but many susceptible ornamental plants, including petunias, asters, dahlias, and zinnias were found grow- ing nearby. The first symptoms, necrotic spots and rings on the younger leaves, were observed the first week of August when the plants were approximately four months old, Ten days later the terminal leaves, bud, and all lateral shoots were wilted and dying. All of the ripening fruits on this plant were mottled and splotched with rings of orange and red. The green fruits were misshapen with necrotic rings and spots. Development of secondary growth ceased. The virus nati gre afte em len cho sea Ma: on sus foli wel eve the Thi str: sec ove obt tha cor tob pan it blig of « soa bli; pre for Th cau wel bla paz Do ma Tp sit; jority 1ission, <irby ive seases pray oril 27; were On mined, The ved up est. here than Smoot hor's nany nd grow- »bserved later ig fruits were e virus Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb., 15, 1952 69 nature of the disease was confirmed by mechanical transmission to young tomato plants in the greenhouse, using expressed sap from stem tissue. Leaf symptoms were observed three weeks after inoculation, Expressed juice from ripe and green fruits were not infective by methods employed. FOLIAGE DISEASES OF CUCURBITS IN THE LOWER RIO GRANDE VALLEY OF TEXAS IN 1951 By G. H. Godfrey Cucurbit downy mildew (Pseudoperonospora cubensis) and powdery mildew (Erysiphe ci- choracearum) were both almost entirely lacking in the 1951 spring crop in this section. The season was almost continuously dry, with 0.08 inches rainfall in February, 0,87 inches in March, and 0.80 inches in April. In May there was only a trace until the 10th, then 1.71 inches on the 11th, and dry again for several days, with 2.43 inches total for the month. Downy mildew was abundant in the limited fall plantings. In the Experiment Station fields, susceptible varieties of cantaloupes such as Hales Best and PMR No. 6 were completely de- foliated before the maturity of any fruit. The downy mildew-resistant selections stood up very well in so far as downy mildew was concerned. Rainfall totaled 4.26 inches, and was fairly evenly divided between the three critical months of August, September, and October, The program of breeding for disease resistance, however, received a severe blow in that there was a severe outbreak of leaf blight (Macrosporium cucumerinum) [=Alternaria cucumerina}, This is the first occurrence of such an epiphytotic in the last 14 years. Some of the cantaloupe strains resistant to downy mildew became heavily infected with Alternaria. It started in a small section of one field from locally grown seed, and during periods of rainy and foggy weather spread over the entire field. A few outstanding plants appeared to be resistant, and selfed seed were obtained from some of them, There was heavy incidence of powdery mildew in a field of Weslaco Strain H cantaloupes that had been planted on the leeward side of a field of squash. The squash was heavily mildewed. Powdery mildew did not occur on five other cantaloupe plots on the Station, It was present on commercial squash fields, and on one late-summer field of commercial cantaloupes. By way of comparison with the occurrence of other downy mildews under the same conditions, tobacco blue mold (Peronospora tabacina) has not yet (December 11) appeared on Nicotiana re- panda growing as a weed in orchard and farm land in the Lower Rio Grande Valley. In past years it has frequently been found at this time of year and later, in winter and early spring. Late blight has not yet been found on fall tomatoes. LOWER RIO GRANDE VALLEY EXPERIMENT STATION, WESLACO, TEXAS SOME OAT DISEASES IN By S. Goto and MINNESOTA 1951 + M. B. Moore During 1951, conditions were very favorable in Minnesota for the observation of leaf diseases of oats. Bacterial stripe, Pseudomonas striafaciens, characterized by exudate on long water soaked lesions was common early in the season, but disappeared soon after heading time. Halo blight, Pseudomonas coronafaciens, persisted somewhat longer but did not seem to cause ap- preciable damage. Victoria blight, Helminthosporium victoriae, which has been inconspicuous for several years, was very severe on Vicland oats growing on peat soil at University Farm. The blackening of the nodes with spore masses was especially noticeable after maturity. Septoria leaf blotch, Septoria avenae, though widespread and at times moderately severe, appeared to cause little damage except in one badly lodged field. The black-stem and black-hull symptoms were not so marked as in some previous years. Anthracnose, Colletotrichum graminicolum, distinguished by its bright orange lesions with black acervuli, was seen in several fields. However, root rot damage by this fungus was not ap- parent. Helminthosporium leaf blotch, Helminthosporium avenae, was present but not damaging. Downy mildew, Sclerospora macrospora, was found at St. Paul for the first time by Dr. H. Asuya- ma, a visitor from Tokyo University, Japan. The oospores were readily observed with a hand lens, by holding the thickened, rough surfaced leaves to the light. 'Paper No, 2783, Scientific Journal SeriesArticle, Minnesota Agricultural Experiment Station, Univer- sityFarm St, Paull, Minnesota ields ings, n 70 Vol. 36, No, 2--PLANT DISEASE REPORTER--Feb, 15, 1952 A hitherto unobserved disorder found generally throughout the State was referred to as "blue dwarf". The affected plants were stunted, with a deep blue green color, shortened flag leaf, blast, and abnormally increased tillering. They occurred at random in fields of all va- rieties. UNIVERSITY OF MINNESOTA, UNIVERSITY FARM, ST. PAUL 1 A CORRECTION Correction -- Anticarie, an effective non-mercurial bunt preventive, marketed by H. P. Rossiger Company, contains 40 percent hexachlorobene instead of 20 percent, as erroneously stated on page 446 of the Reporter, issued October 15, 1951. -- R. W. Leukel | 40 x .Vva- ly OBSERVED TEMPERATURE ANOMALY (APPROXIMATE) DECEMBER 1951 OBSERVED PRECIPITATION (APPROXIMATE) DECEMBER 1951 The terms used in the accompanying maps, which define the ranges of temperature and precipitation, are numerical class limits. These are based on a statistical analysis of past records through which is determined the normal frequency of occurrence of temperatures and precipitation at various times of the year for different locations. For temperature the classes above, below, and near normal are so defined that they each normally occur one-fourth of the time; much above and much below normal, one-eighth of the time. Precipitation is depicted in terms of light, moderate, and heavy, each class normally occurring one-third of the time and thereby having equal probability of occurrence. These maps graphically represent only the general trends and give the country's weather picture at a glance. For quantitative studies, where monthly mean temperatures and actual precipitation records are needed for a given time and place, other publications of the Weather Bureau should be consulted. P. R. M.