Survey of diseases of glasshouse tomato crops in England and Wales in 1976

Abstract

SUMMARYOne hundred and forty‐six tomato crops throughout England and Wales were assessed for diseases. The commonest fungus pathogen was Botrytis cinerea Pers. ex Fr. which caused stem lesions in 64 per cent of the crops, leaf lesions in 38 per cent and fruit ghost spot in 46 per cent. Benomyl tolerance was widespread in isolates of this pathogen and was detected in 50 of the 68 crops examined. Seventy‐seven per cent of isolates from crops sprayed with a methyl benzimidazole carbamate (MBC) fungicide were tolerant compared with 34 per cent from crops where these fungicides had not been used. Fulvia fulva (Cooke) Ciferri was found in 28 per cent of the crops but was severe in only three per cent. Didymella lycopersici Kleb. occurred in seven per cent of the crops. Tomato mosaic (TMV) symptoms were seen in 34 per cent of the crops, although 47 per cent of those surveyed were of resistant cultivars in which no virus symptoms were seen. The Dutch avirulent TMV strain MII‐16 was used for crop protection on 27 per cent of the nurseries. TMV strains collected from crops with symptoms were predominantly strain 1 (85 per cent) and 96 per cent of isolates from crops inoculated with MII‐16 were of this strain. No new strains or tobacco forms of TMV were found.Root rots were extremely common at the end of the crops, varying in intensity according to the pre‐planting soil treatment. Steam treatment was most effective (28 per cent root rot) with methyl bromide the next best (30 per cent), followed by dazomet (42 per cent). Methyl bromide was used by 45 per cent of growers, whereas 17 per cent used steam and 11 per cent dazomet. Peat‐bag culture was used on five per cent of the nurseries. In peat‐bag culture there was little root rot (11 per cent). Verticillium spp. were isolated from 25 per cent of crops in the survey and Fusarium oxysporum Schl. from eight per cent. Chimeras were found in 34 per cent of the crops, but only in 1.1 per cent of the affected plants was the chimera affecting the growing point and likely to affect yield. There was a tendency for early‐planted crops to have a greater incidence of chimera. Generally the cultural factors recorded did not appear to be connected with disease incidence, but there was a significant increase in the amount of Botrytis in the stopped plants. Benomyl, either as a spray or a drench, was the most commonly used fungicide, but more than a third of the crops did not receive any fungicidal treatments.