“SLEEPY DISEASE” OF THE TOMATO1

Abstract

SUMMARY. 1. “Sleepy Disease” or “Wilt” of tomatoes may Joe caused by one of two fungi, Fusarium lycopersici or Verticittium albo‐atrum. Massee's “diplocladium stage” of F. lycopersici has been shown to be V. albo‐atrum. The wilt producing fungi attack the roots and grow up through the vascular bundles into the stem, leaves and sometimes the fruits. The wood of a diseased plant is a light or dark brown colour. The average temperature is a “limiting factor” in determining which fungus is active. F. lycoperstci grows best at an average temperature of 27‐8‐28‐9oC. If the temperature remains constantly much below this, little infection results. V. albo‐atrum develops well at temperatures from 15‐6‐24‐0oC, being most active at 2M‐22‐8oC. Above an average temperature of 25oC. little infection occurs. 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 V. albo‐atrum, which accordingly is the most important cause of wilt. Wilted plants soon die under conditions of low temperature, but if the average temperature be raised above 25oC, 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. V. albo‐atrum from tomato readily induces wilt in the potato, eggplant, snapdragon, cotton, pepper plant and cucumber, and produces a stunted condition of the sycamore and elm. A number of different strains of V. albo‐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. 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. 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 susceptible to attack. Most varieties of tomatoes cultivated in this country are susceptible to Vertidllium, but Manx Marvel has proved to be practically immune and Bides' Recruit highly resistant. Certain cultural devices, including regulation of the temperature and shade, have been devised which assist “wilted plants” to recover. Further investigations upon soil sterilisation and the production of resistant varieties are in progress.