132 ''Sleepy Disease'' of the Tomato 



from 15-6-24'0° C, being most active at 2M-22-8° C. Above an average 

 temperature of 25° C. little infection occurs. 



5. The average temperature conditions existing in glasshouses in this 

 country are generally too low for F. lycopersici and consequently it is 

 rarely found as a cause of tomato wilt. The relatively low temperatures 

 are favourable to F. alho-alrum, which accordingly is the most important 

 cause of wilt. 



6. Wilted plants soon die under conditions of low temperature, but 

 if the average temperature be raised above 25° C, they recover and will 

 bear a crop so long as the high temperature is maintained. When the 

 temperature again drops, wilt reappears and death results. 



7. F. alho-atrum from tomato readily induces wilt in the potato, egg- 

 plant, snapdragon, cotton, pepper plant and cucumber, and produces 

 a stunted condition of the sycamore and elm. 



8. A number of different strains of F. alho-atrum have been isolated 

 which vary in their rate of growth, the amount and rate of production 

 of microsclerotia, and in colour production; but no evidence has been 

 obtained to show that there may be different strains restricted to different 

 varieties of tomatoes. 



9. In pure culture the fungus has been shown to produce a large 

 number of enzymes and there are strong indications that substances of 

 a toxic nature play an important part in producing wilt. 



10. There is a distinct relation between hardness of growth and 

 susceptibility to wilt; the harder growing varieties and plants suffering 

 from starvation or a severe check in the young stages being most sus- 

 ceptible to attack. Most varieties of tomatoes cultivated in this country 

 are susceptible to Verticillium, but Manx Marvel has proved to be 

 practically immune and Bides' Recruit highly resistant. 



1 1 . Certain cultural devices, including regulation of the temperature 

 and shade, have been devised which assist " wilted plants " to recover. 



12. Further investigations upon soil sterilisation and the production 

 of resistant varieties are in progress. 



APPENDIX. 



Since this paper was written, a wilt disease of the sweet-pea has 

 occurred in certain commercial nurseries where this crop is grown in the 

 early part of the year before a tomato crop. The young seedlings showed 

 first symptoms when about 6 inches high, the lower leaves turning yellow 

 and withering. The desiccation advanced rapidly to the top of the 

 seedlings, which then died. Verticillium alho-atrum was isolated and 



