piiipfc -^ ';=:- i4^i»r'' L I B R.AFLY OF THE U N IVERSITY or ILLI NOIS cop ,2 ./viUHAL HISTORY SURVEY i STATE ^F ILLINOIS Otto Kerner, Governor 9 * % PARTM m Sylvester White, Director %U OF ILMNlblS J. L. FORSBER «,/ k« S^i*.V^ rcAL [Civil a Ml ^ M tit • *■ J- « «' • %/ # #^ SUIlVSY PVISIOh% '• ♦ ^ ^ '^ .t«* "^ U*ana- lUin.i5 '•— - -hief ^ A |k% ♦ - i * «t «*^ Moreh,196i' •#>,! _ Fig. 1. --Fisher constant temperature bath used in tests on heat tolerance of gladiolus pathogens This apparatus was used also for most of the hot -water treatments on gladiolus cormels. HOT-WATER AND CHEMICAL TREATMENT OF ILLINOIS-GROWN GLADIOLUS CORMELS J. L. FORSBERG* The hot-water treatment of gladiolus cormels as a method of eliminating cer- tain fungus pathogens has received considerable attention recently from plant pathol- ogists and commercial gladiolus grower s. The first report on the use of this method was made by Roistacher (1951) , who treated senr^idormant cormels of six gladiolus varieties for 30 minutes at temperatures between 1 31 and 140 degrees F. In semidor- mant cormels subjected to the hot-water treatment at 135 degrees, germination was 40 per cent less than in untreated cormels; in similar cormels subjected to the treat- ment at 137 degrees, germination was 75 per cent less than in the untreated checks. Preliminary tests to determine the thermal death point of Fusarium oxysporum var, gladioli in gladiolus cormels indicated that this point "is close to the temperature fRat critically reduced germination of the cormels." Bald & Markley (1955) reported that control of Fusarium and other diseases was attained on a field scale when the hot-water treatment was applied to growers' lots of gladiolus cormels. They cautioned, however, "For successful treatment, cormels had to be harvested from warm soil after growth during sunnmer." The hot-water treatment was recommended with reservations by Bald (1956), who stated, "Cormels that have withstood treatnnent undamaged have so far been from plants grown in a warm dry climate during summer, and matured and harvested be- fore the onset of cold weather. Cormels grown in cooler climates, or grown and harvested during the cooler season in a warm climate, have not yet survived the re- quired temperature." Bald, Ferguson, & Markley (1956) gave detailed instructions onuse of the hot- water treatment and cited a case in which a badly diseased lot of Spotlight gladiolus cormels was so successfully treated that the disease appeared in less than 0.5 per cent of the resulting plants. Ivlagie (1956) reported that the hot-water treatment of gladiolus cormels had been tested in Florida since 1953. He stated further that "A 30 -minute soak at 53. 5° C killed the following fungi in cormel-size pieces of diseased tissue cut from cormst Fusarium oxysporum Schlect. f. gladioli (Massey) Snyd, & Hans. , Stromatinia glad- ioli (Drayt.) Whet., and Curvularia lunata (Wakk.) Boed. " Chemical treatments of cormels had been used in Illinois for many years, but all of the experimental work on, as well as commercial use of, the hot-water treatnnent had been in California and Florida, and no information was available on effects of using hot-water treatments on Illinois -grown cormels. Because gladiolus growers in Illinois suffer losses every year from the Fusarium, Curvularia, and Stromatinia diseases, it seemed desirable to determine if the hot-water treatment could be used successfully in this state. It also seemed desirable to compare the effectiveness of hot-water treatments with a standard chemical treatment and to ob- tain some fundamental information onheat tolerances of the gladiolus pathogens. Re- sults of tests designed to obtain this information are reported in this paper. *J. h. Forsberg is Plant Pathologist, Illinois Natural History Survey. Photographs for this paper were made by William E. Clark. The nnanuscript was edited by James S. Ayars. PRELIMINARY TEST A preliminary test on survival of hot-water -treated Illinois -grown cormels was made in 1956 on a commercial gladiolus grower's farm in Kankakee County, Illinois. The cormels were treated in a specially built insulated treating tank with temperatures of circulating water thermostatically controlled within 0.5 degree F, of the desired temperature. Because the equipment was not ready to use until after mid-June, the treatments were not made as early as had been intended. Cormels were treated June 20 and 11 and planted June 22. The following treatments were used on cormels of the gladiolus varieties Debonair, Spic and Span, and Margaret Fulton: hot-water at 131 degrees for 30, 45, and 60 minutes; hot-water at 125 degrees for 4 hours; hot-water at 135 degrees for 10, 20, and 30 minutes; New Improved Ceresan, one -half pound in 25 gallons of water at air temperature for 1 hour. An additional treatment in water at 110 degrees for 23 hours was used on one variety. One 1 -pound coffee can, level full, of cormels was used as a treatment lot. Sixteen feet of row were used for planting each lot of cormels. Results of this test are shown in tables 1, 2, and 3. Although germination was reduced by the heat treatments and there was a pro- gressive reduction in germination as temperatures andtreating times were increased, in none of the lots were all of the cormels destroyed by the hot-water treatments. Since the cormels were probably far out of their dormancy at the time of treatment, the results were not discouraging. As the cormels were planted in a field where diseased gladioli had been present, little significance can be attached to the amount of rot which developed in the various lots. HEAT TOLERANCES OF GLADIOLUS PATHOGENS In the winter of 1956-57 laboratory tests were conducted on heat tolerances of gladiolus pathogens. These tests were carried out with the help of Raymond E. Wilken, then Technical Assistant, Illinois Natural History Survey. Cultures of Fusarium oxysporum f. gladioli (Massey) Snyd. Si Hans. , Curvularia trifolii (Kauffm.) Boed. rr'gladioli Parm. h. Lutt. , and Stromatinia gladioli (Drayton) Whet., which had been isolated originally fronn diseased tissues of gladiolus corms, were subcul- tured on potato dextrose agar in petri dishes and incubated at 24 degrees C. Fusarium and Curvularia cultures were incubated 10 days and Stromatinia cultures 2 weeks before being used in the heat tolerance tests. Twenty-six isolates of Fusarium , 12 isolates of Curvularia, and 3 isolates of Stromatinia were used in the tests. Alto- gether 270 individual tests were made. The various isolates of the three organisms were subjected to a series of heat treatments in which the following procedure was used for each test: Six test tubes, each containing? ml. of distilled water, were suspended in an automatic Fisher con- stant temperature bath, fig. 1. All tubes were allowed to reach a preselected tem- perature before inoculum was added. The petri dish subculture of the organism to be tested was dispersed for 30 seconds in a Waring Blendor containing 200 ml. of distilled water. Five drops of the dispersed culture were then added to each of the six tubes in the water bath. At the end of each of three periods, (15, 30, and 60 minutes) one pair of test tubes was removed from the water bath and the contents of each tube was poured into a petri dish containing potato dextrose agar. After the dishes had stood for a few seconds to allow the solid particles to settle, the water was poured off. Checks were prepared by adding five drops of the dispersed culture to 7 ml. of water in a test tube, shaking the tube for a few seconds, and then pouring the contents into a petri dish containing potato dextrose agar. After the solid parti- Table 1. --Effect of hot-water and New Im- proved Ceresan treatments of Debonair cormels, as indicated by number of corms produced and per cent of corms rotted. C orms Pe r Cent of Treatment Produced Corms Rotted 131°F., 30 minutes 820 43.9 131°F. , 45 minutes 532 33.8 131°F. , 60 minutes 388 14.2 125°F. , 4 hours 122 0.0 135°F. , 10 minutes 828 11.2 135°F. , 20 minutes 459 1.8 135°F. , 30 minutes 146 4.1 New Improved Ceresan 1 032 14.3 No treatment 1 203 26.1 Table 2. --Effect of hot-water and New Im- provedCeresan treatments of Spic and Span cormels, as indicated by number of corms produced and per cent of corms rotted. Corms Per Cent of Treatment Produced Corms Rotted 131°F. , 30 minutes 612 11.8 131°F. , 45 minutes 700 8.6 131°F. , 60 minutes 649 3.2 125°F. , 4 hours 172 0.0 135°F. , 10 minutes 1,248 0.9 135°F. , 20 minutes 670 3.3 135'*F. , 30 minutes 459 1.5 110°F. , 23 hours 1,490 0.7 New Improved Ceresan 1,2 60 6.3 No treatment 1,240 3.9 Table 3. --Effect of hot-water and New Im- provedCeresan treatments of Margaret Fulton corm- els, as indicated by number of corms produced and per cent of corms rotted. Corms Pe r Cent of Treatment Produced Corms Rotted 1310F. , 30 minutes 1,504 21.5 1310F. , 45 minutes 1.324 19.8 1310F. , 60 minutes 1,312 21.6 1250F. , 4 hours 466 2.8 1350F. , 10 minutes 1,443 10.4 135°F. , 20 minutes 1,108 1.6 135°F. , 30 minutes 712 1.7 New Improved Ceresan 1,742 5.6 Fig. 2. --Colonies of Fusarium oxysporum f. gladioli isolate 55 -31 developed from inoculum exposed to room temperature (upper left), 135 degrees F. for 15 minutes (upper right), 135 degrees for 30 minutes (lower left), and 135 degrees for 60 minutes (lower right). Fig. 3. --Colonies of Fusarium oxysporum f. gladioli isolate 55 -28 developed from inoculum exposed to room temperature (upper left), 137 degrees F. for 15 minutes (upper right), 137 degrees for 30 minutes (lower left), and 137 degrees for 60 minutes (lower right). Table 4. --Effect of various temperatures on six Fusarium isolates grown on potato dextrose agar, as indicated by "number of colonies developed after being heated 15, 30, or 60 minutes. Isolate Temperature in Degrees F. 15 Minutes Exposure Tinne 30 Minutes 60 Minutes 55-8 55-12 55-15 55-31 55-52 55-69 135 136 137 135 136 137 138 139 130 131 135 136 137 138 139 137 138 135 136 137 138 * 70 * * * 8 2 14 * 75 16 22 2 30 42 57 2 2 30 8 75 42 40 2 1 3 81 57 1 3 30 17 9 3 12 2 7 1 11 1 1 ''Colonies too numerous to count. cles had settled, the water was poured off. The cultures were incubated at 24 de- grees C, for 6 days, and the colonies growing on each plate were counted, figs. 2 and 3. Later, similar tests were made in whichheat periods of 1, 2, 3, 4, 5, 6, 24, and 48 hours were used. Stromatinia cultures grew poorly after they had been dispersed in the Waring Blendor"! Because of this poor growthwhole oats were tried as media for the subcul- tures of Stromatinia. Later Curvularia and Fusarium also were grown on oats. Table 5. --Effect of various tennperatures on two Fusarium isolates grown on whole oat grains, as indicated by number of grains in which fungus sur\-ived after being heated 15, 30, or 60 minutes. Isolate Temperature in Degrees F. 15 Minutes Exposure Time 30 Minutes 60 Minutes 55-52 55-62 140 142 143 134 135 136 137 6 1 In the preparation of the oat cultures the oats, in Erlenmeyer flasks, were soaked for several hours and then autoclaved 1 hour. After cooling, the oats in the flasks were inoculated with the disease organisms and the cultures incubated 10 to 14 days . During this period the flasks were shaken daily to prevent the oats from clumping. Four infested oat grains were dropped into 7 ml. of preheated distilled water in each of several test tubes, placed in the water bath, and removed after specified periods of time, as described for treatment of subcultures on potato dextrose agar. After the heat treatments the four oat grains in each tube were embedded in agar and incubated. The dishes were examined for fungus growth after 4 to 6 days. When Fusarium cultures grown on potato dextrose agar were kept in the water bath for 30 nninutes, the temperature necessary to completely destroy the organisms varied from 131 degrees F. for isolate 55-15 to over 139 degrees for isolates 55-12 and 55-31, table 4. When grown on whole oat grains, isolate 55-52 was not com- pletely destroyed by treatments below 143 degrees, table 5. Only two isolates were subjected to heat treatments for 24 and 48 hours. Isolate 55-52 was destroyed by a treatment at 125 degrees F. in 24 hours. A 48-hour exposure to 120 degrees weak- ened the culture but did not destroy it. Isolate 55-62 was weakened when subjected to 120 degrees for 24 hours and killed at 120 degrees F. in 48 hours. Curvularia cultures were more uniform in their tolerance to heat than were Fusarium cultures. All isolates of Curvularia tested were killed in 30 minutes at 132 to 04 degrees F. Only two isolates were treated for longer periods and both were killed in 24 hours at 123 degrees, but not at 122 degrees. All three isolates of Stromatinia tested were killed in 30 minutes at 124 de- grees F. The three isolates reacted similarly to long-time exposures, being killed in 24 hours at 105 degrees F. CORMEL TREATMENTS Bald (1956) stated, "Tolerance to high temperatures seems to arise from the initiation of full dormancy by warm growing conditions. Cormels maturing under cool conditions become only partially dormant." He stated further, "The most fa- vorable time for treatment of cormels is about 2 to 4 months after digging. " In the winter of 1956-1957 a test was made to determine if there was a time at which Illinois -grown cormels could withstand the hot-water treatment. Cormels of six varieties which had been dug in early October were divided into lots, the corm- els of each variety into six lots. Each lot of a variety contained approximately the same number of cormels. No attempt was naade to use the same size lots for all va- rieties. One lot from each variety was treated in hot water at 135 degrees F. for 30 minutes on Novennber 30. This treatment was selected because it is recommended in some gladiolus -growing areas of California and Florida. Subsequent lots were treated December 22, January 31, February 27, and March 27. One lot was left un- treated to serve as a check. The cormels were kept in the laboratory at a tempera- ture of about 75 degrees F. from November 1 until treated. They were kept at 40 degrees F. from the time they were treated until May 13, when they were removed to a commercial gladiolus grower's warehouse andkept thereuntil planted on May 23. Results of this experiment are shown in table 6. The varieties varied con- siderably in their tolerance to the heat treatments. As indicated by yields of corms from the cormels, none of the varieties withstood the November 30 heat treatments Date Corms Per Cent of Variety Treated Produced Corms Rotted Beacon 3''5 9.6 Nov. 30 186 2.7 Dec. 22 387 5.4 Jan. 31 602 2.7 Feb. 27 551 5.3 March 27 594 5.7 Benjamin Britten 105 12.4 Nov. 30 52 3.9 Dec. 22 160 7.5 Jan. 31 235 11.9 Feb. 27 290 2. 1 March 27 423 4.3 Mother Fischer 230 11.3 Nov. 30 128 20.3 Dec. 22 240 15.8 Jan. 31 240 14.6 Feb. 27 125 6.4 March 27 133 8.3 Nancy 415 25.1 Nov. 30 35 0.0 Dec. 22 128 17.2 Jan. 31 282 13.1 Feb. 27 120 4.2 March 27 105 1.9 Spic and Span Nov. 30 112 23.2 Dec. 22 385 10. 1 Jan. 31 207 18.4 Feb. 27 164 5.5 March 27 151 5.3 Spotlight 551 18.3 Nov. 30 424 32.6 Dec. 22 626 21.6 Jan. 31 784 36.0 Feb. 27 776 24.9 March 27 543 37.? well. If gladiolus cormels can best withstand heat treatments when the cormels are nearest complete dormancy, the results of this experiment show that cormels of all varieties do not become dormant at the same time. The period of greatest dormancy in Mother Fischer and Spic and Span was reached by December 22, in Beacon, Nancy, and Spotlight by January 31, and in Benjamin Britten by March 27, In Mother Fischer and Nancy the period of greatest dormancy had passed by February 27, in Spic and Span by January 31, and in Spotlight by March 27. The period of greatest dormancy in Beacon and Benjamin Britten had notpassed by March 27. Results of this experi- ment agree, at least in part, with the observation of Roistacher, Bald, h Baker | (1953), who stated that capacity for germination, that is, breaking of dormancy, may ' be rapid or slow, depending on the variety and the conditions of storage or treatment. , When yields of corms from treated cormels were compared with yields from the untreated checks it was found that the amount of rot in 17 of 25 treated lots was Table 6. --Effect of date of hot-water treatment of cormels, as indicated by number of corms pro- duced and per cent of corms rotted. less than that in the corresponding untreated checks. As the corms from the un- treated check of Spic and Span were lost, no comparison couldbe made in this variety. Because some growers had been treating cormels at 110 degrees F. for 24 hours, a connparison of the effectiveness of 110-degree and 135-degree treatments was made, Cormels of four varieties were divided into three lots each. The first lots were not treated, the second lots were treated at 135 degrees for 30 minutes on March 15, and the third lots were treated at 110 degrees for 24 hours on May 9. Results of this test are shown in table 7. The hot -water treatments reduced the yields of corms in all cases; the 135-degree treatment reduced the yields much more than did the 110-degree treatment. In all varieties the percentage of rot was less in corms fronn cormels treated at 135 degrees than in those treated at 110 de- grees. The 110-degree treatment had little or no effect upon the disease. In 1958 an attempt was made to find out to what extent storage conditions be- fore treatment affect cornnel dormancy and thus affect results obtained with the hot- water treatment. Also, an attempt was made to find out if a chemical treatment would be as satisfactory as the hot-water treatment. Cormels of nine varieties in a com- mercial warehouse were divided into lots, the cormels of each variety into six lots. Lots 1 and 2 of each variety were taken from the warehouse to the laboratory on Jan- uary 7. Lot 1 was given the hot-water treatment, 135 degrees F. for 30 minutes, on January 16. Lot 2 was kept in the laboratory at a temperature of 75 to 80 degrees F. until February 12, when it was given the hot-water treatment. Lot 3 was taken from the warehouse on February 11 and hot-water treated on February 13. After the treated cormels were dried they were stored at 40 degrees F. until 1 week before being planted. Lots 4, 5, and 6 were kept in the warehouse until May 8. On that date lot 4 was soaked 2 1/3 hours in Emmi 1:400 at 50-54 degrees F. Lot 5 was soaked 2 hours in Emmi 1:400 at 105 degrees F. Lot 6 was not treated. All cormels were planted May 8. Results of this test are shown graphically in figs. 4, 5, and 6. In all nine va- rieties fewer corms were obtained from lot 3 than from lot 2. In eight of the nine varieties fewer cornns were obtained from lot 1 than from lot 2. Lot 2 was the only Table 7. --Effect of 135 and 110 degrees F. treatments on cormels, as indicated by number of corms produced and per cent of corms rotted. Variety Treatment Date Corms Produced Pe r C ent of Corms Rotted 18 1 4 1 37 5 11 2 9 3 23 2 16 4 24 9 7. 4 33 3 Hans Van Meegrin Harry Hopkins Lady Jane Sans Souci None 135°F. 30 minutes March 15 110°F. 24 hours May 9 None 135°F. 30 minutes March 15 110°F. 24 hours May 9 None 135V. 30 minutes March 15 110^. 24 hours May 9 None 135°F. 30 minutes March 15 110°F. 24 hours May 9 896 146 800 224 12 54 858 102 556 652 84 318 I lot which was kept in a warm, dry room before treating. These results indicate that cornnels kept in a warm, dry room generally withstand the hot -water treatment better than cormels kept in the cool, moist atmosphere of a commercial warehouse. In six of the varieties both lots of Emmi -treated cormels produced more rot- free cor ms than any of the hot-water -treated lots. Also, Emmi -treated lots produced more diseased corms than the hot-water -treated lots. The hot-water treatment re- duced the amount of disease, but it also reduced germination of the cormels. In seven of the nine varieties cormels given the cold Ennmi treatment pro- duced more rot-free corms than did the cormels given the warm Emmi treatment. In the varieties Benjamin Britten and Elizabeth the Queen more rot-free corms were obtained from cormels given the warm Emmi treatment than from cormels given the cold Emmi treatment. In another experiment the hot -water treatment was compared with cold and warm Emmi treatments on cormels of six gladiolus varieties. The following treat- ments were used on each variety: (1) hot water at 135 degrees F. for 30 minutes; (2) Emmi 1:400 at 50-54 degrees F, for 2 1/3 hours; (3) Emmi 1:400 at 105 degrees F. for 2 hours; (4) untreated check. The cormels of each variety were divided into four equal parts by volume. No attennpt was made touse the same number of cornnels for all varieties. The hot- water treatments were made on December 19, 1957; the treated cormels were then dried and stored at 40 degrees F. until 1 week before planting. The Emmi treatments were made on May 8, 1958, the day all the cormels were planted. Results of this experiment are shown in figs. 7 and 8. In five of the six va- rieties more rot -free corms were obtainedfrom cornnels given the Emmi treatments than from cormels given the hot-water treatments. The hot-water treatments were superior to the Emmi treatnnents only in the variety Leif Ericson. In three of the va- rieties more rot-free corms were obtained fronn cormels treated inwarnn Emmi than from cormels treated in cold Emmi. In the other three varieties the reverse was true. In five of the six varieties the least annount of disease was found incornns pro- duced fronn cornnels that had received the hot-water treatment. DISCUSSION From the results obtained in the experinnents reported here, it may be con- cluded that the hot-water treatment can be used beneficially on Illinois -grown cornn- els under certain conditions. The hot-water treatment will eliminate Fusarium and Curvularia fronn a stock of cornnels to a greater extent than will a chennical treatnnent. However, the hot-water treatment may reduce corm yields sonnuch that the value of the treatment becomes questionable. Use of a chemical treatnnent, while not reducing the annount of disease percentagewise as much as the hot-water treatment, generally will result in a greater yield of rot-free cornns than would be obtained with the hot- water treatment. The hot-water treatment nnight be of greatest benefit in cleaning up a badly diseased lot of cornnels to give the grower a new start with a snnal I annount of relatively disease -free planting stock. 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