Surrey of Diseases of Glasshouse Tomato Crops in Yorkshire and Lancashire in 1974 and 1975

Abstract

SUMMARYEighty‐one tomato crops were assessed for diseases in 1974 and 50 in 1975. The commonest fungus disease was Botrytis cinerea, which caused stem lesions in 90 and 66 per cent of the crops, leaf lesions in 84 and 98 per cent and fruit ghost spot in 94 and 94 per cent in the two years respectively. Benomyl tolerance was widespread in isolates of this pathogen, showing little decline in the two years in spite of the reduced use of benomyl and other similar fungicides in 1975. Fulvia fulva was severe in one crop in 1974 and in three in 1975; Didymella lycopersici was found in only one crop in 1974 and three in 1975. Tomato mosaic symptoms were seen in 73 and 66 per cent of crops in each year respectively. The use of an avirulent strain of tobacco mosaic virus (TMV) for the purpose of cross‐protection decreased from 53 per cent in 1974 to 34 per cent in 1975. Nurseries with at least some TMV‐resistant cultivars increased from 51 per cent in 1974 to 64 per cent in 1975. TMV tomato Strain 1 was the most commonly identified strain. No new strains or tobacco forms were recorded.Root rots were extremely common and their severity was closely connected with pre‐planting soil treatment. Steam treatment gave the best control followed by methyl bromide and dazomet. The use of methyl bromide increased and the use of steam decreased in 1975. Verticillium wilt was found in 16 and 15 crops and fusarium wilt in two and three crops respectively in 1974 and 1975.Fungicides were used on 74 and 56 per cent of crops in 1974 and 1975 respectively, the decrease in 1975 being largely attributable to the decline in the use of benomyl.