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. 



