Effects of foliar fungicide sprays on disease and yield of processing tomatoes in Ontario

The effects of controlling foliar diseases with a foliar fungicide applied following a TOMCAST regime were evaluated on commercial processing tomato (Lycopersicon esculentum Mill.) cultivars in three locations in Southwestern Ontario in 1990 and 1991. For each cultivar, one set of plants was sprayed with chlorothalonil (Bravo 500) and one set received no fungicide application during the growing season. At two of the three locations, fungicide application significantly reduced final foliar disease development, averaged across all cultivars, from over 60% of the foliage infected to 10% infected. At the third location disease development was more restricted. Use of foliar fungicide did not result in a significant increase in either total fruit yield or yield of marketable fruit measured across cultivars, years, and locations. The application of fungicide (4–10 sprays) reduced the average number of fruit infected with anthracnose by 50% over all cultivars treated. Several cultivars, however, had relatively low levels of anthracnose even without fungicide sprays. While fungicide sprays may be important in maintaining fruit quality, both with respect to solids levels and degree of mould contamination, fungicide may not be required to maintain yields every year for many tomato cultivars commercially grown in Ontario. Key words: Lycopersicon esculentum, tomato disease, anthracnose