els subjected to warm, dry storage conditions will withstand the hot -water treatment 

 much better than will cormels which have been kept in the cool, moist atmosphere of 

 a commercial warehouse, growers who wish to use the hot-water treatment should 

 transfer their cormels to warm, dry quarters at least a month before subjecting them 

 to the hot-water treatment. 



Although treating cormels at 135 degrees F, for 30 minutes, a recommended 

 treatment in California and Florida, may do much toward reducing the amount of dis- 

 ease in the subsequent crop, it is conceivable that use of this treatment year after 

 year might eventually increase, rather than reduce, the amount of disease in gladio- 

 lus planting stock. These experiments have shown that all isolates of Fusarium are 

 not killed in 30 minutes at 135 degrees F, Thus, if such heat-resistant strains sur- 

 vived the treatment they might continue to develop in a gladiolus stock until the heat 

 treatments would become entirely ineffective, 



Roistacher, Baker, & Bald (1957) do not agree with this view. They contend 

 that "Everything considered, it is unlikely that Fusaria of such thermal tolerance 

 as to render the treatment ineffectual will appear. However, since cormels in aprop- 

 er state of dormancy can often tolerate temperatures well above 135 degrees F. . . . 

 there is still some margin of safety. " 



Ryan (I960), quoting Dr. Robert O. Magie of the Gulf Coast Experiment Sta- 

 tion, Bradenton, Florida, stated, "Corona and Leading Lady cormels have been 

 treated at 135°F for several years, and a large stock of cornnels has been built up. 

 However, it was found lastyearthat this treatmentwas not effective in destroying all 

 of the Fusarium infection, and the corms began to break down when grown from planting 

 stock or after reaching No, 1 size. Last summer. Corona and Leading Lady corm- 

 els were treated at temperatures up to 1 39 degrees F for 30 nnin. The smaller corm- 

 els tolerated the highest tennperature used and are growing in the field." 



The report from Magie supports the contention that heat-resistant strains of 

 Fusarium can survive and continue to develop in a gladiolus stock until the heat treat- 

 ments become ineffective. This hazard might be avoided, as Magie has suggested, 

 by increasing the treating temperature from 135 to 139 degrees F, Such a procedure, 

 however, would reduce germination in many stocks of gladiolus cormels so much that 

 it would be unwise to use the method as a regular commercial practice. 



LITERATURE CITED 



Bald, J. G. 1956. Development and production of pathogen -free gladiolus cormels. U. S. Dept. Ag. Plant 

 Dis. Reptr. Sup. 238:81-4. 



Bald, J. G. , John Ferguson, and B. B. Markley. 1956. Treatment of gladiolus cormels. Calif. Ag. 10(6): 

 15-6. 



Bald, J. G. , and Brian B. Markley. 1955. Application of hot-water treatment to growers' lots of gladiolus 

 cormels. (Abst.) Phytopathology 45(12):693. 



Magie, R. O. 1956. Hot water treatment for controlling gladiolus corm-borne pathogens. (Abst.) Phytopa- 

 thology 46(1):19. 



Roistacher, Chester N. 1951. Hot-water treatment of gladiolus cormels. (Abst.) Phytopathology 41(10):°43. 



Roistacher, Chester N. , Kenneth F. Baker, and J. G. Bald. 1957. Hot-water treatment of gladiolus corm- 

 els for the eradication of Fusarium oxysporum f. gladioli . Hilgardia 26(1 7):65Q-84. 



Roistacher, C. N. , J. G. Bald, and K. F. Baker. 1953. The tetrazolium test for dormancy and germina- 

 bility of gladiolus cormels. Science 1 1 8(3059): 1 86 -7. 



Ryan, R. W. I960. 1959 (15th) report of the Joint Research Committee, NAGC-NACGG. N. Am. Glad. Council 

 Bui. 61:31-6. 



12 



