Effect of Foliar Fungicide Treatment on Early Blight and Yield of Fresh Market Tomato in Ontario. Ronald A. Brammall, Horticultural Research Institute of Ontario, Horticulture Experiment Station, Box 587, Simcoe, Ontario, N3Y 4N5. . Plant Dis. 77:484-488. Accepted for publication 14 December 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0484.

A 2-yr field study investigated the effects of a FAST-based fungicide application regime (TOMCAST) employing chlorothalonil on early blight severity and yield of 13 fresh market tomato cultivars commercially grown in Ontario. During both years, applications of chlorothalonil decreased early blight severity, measured either as area under the disease progress curve (AUDPC) or as the last disease rating (LDR) made in late August. However, applications did not affect the yield of any cultivar, nor were fungicide–cultivar interactions detected. Cultivars differed in the extent of defoliation resulting from early blight. Disease severity (AUDPC) in the cultivar Celebrity was not affected by fungicide application. Generally, weight, number of fruit harvested, and the mean fruit weight varied significantly among cultivars.