130 ''Sleepy Disease'' of the Tomato 



by suitably increasing the boiler heat, regulating the ventilation and 

 closing the ventilators for two to four hours in the middle of the day. 

 A light dressing of whitewash on the glass makes the conditions still 

 more favourable for the plants. As little water as possible should be 

 given to the roots as this aggravates the wilting, but a light overhead 

 damping is beneficial. The development of fresh roots should be en- 

 couraged by mulching the base of the plant. 



On one nursery 78 per cent, of the plants were showing symptoms 

 of wilt disease before the above methods were enforced : a fortnight later 

 only 10 per cent, remained wilted. In view of the fact that low spring 

 temperatures favour infection by VerticilUum, some advantage might be 

 gained by planting later than is usually done, so that the higher summer 

 temperatures may arrive before the plants are infected. . 



2. The elimination of sources of infection. 



Edgerton (lO) has pointed out that F. lycopersici develops much more 

 rapidly in sterihsed soil than in ordinary unsterihsed soil. This has been 

 found true for F. albo-atrum, for plants growing in imperfectly sterihsed 

 soil or re-inoculated sterilised soil yield a higher percentage of disease 

 than those in unsterihsed soil. This relation is accentuated if the soil be 

 exceedingly rich in humus, as is the case with sterihsed cucumber soil so 

 frequently used for tomato propagation. The determination and elimina- 

 tion of infection thus becomes of vital importance. The fungal out- 

 growths at the base of dead diseased plants produce innumerable spores 

 which become widely disseminated. These in themselves will not carry 

 the fungus over the period of winter, but they readily germinate, and 

 feeding on decaying plant material produce carbonised hyphae and 

 microsclerotia, which are able to withstand winter conditions. Examina- 

 tion has been made of small pieces of plant remains, unearthed from 

 nursery soils after the crop has been removed, and numerous tomato 

 pathogens including F. albo-atrum have been found upon them. Thus it 

 is important to remove completely all plants killed by wilt disease before 

 cleaning up the nursery when the crop is finished and to remove carefully 

 as much as possible of the general debris. The best way to remove the 

 crop, when completed, is to sever each plant about 3 inches from the soil 

 and remove all the aerial portions including leaves, etc., which have 

 fallen to the ground, before attempting to remove the roots. If the 

 surface is quite clean before the roots are removed, there is less chance 

 of incorporating diseased material in the soil and the roots may then be 

 carefully taken up, leaving behind only the very fine rootlets. 



