Validation of an Early Blight Forecasting System for Tomatoes. S. P. Pennypacker, Associate Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. L. V. Madden, Former Graduate Assistant, and A. A. MacNab, Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Plant Dis. 67:287-289. Accepted for publication 22 July 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-287.

A forecasting system (FAST) for Alternaria solani on tomato (Lycopersicon esculentum) was validated during the 1978 and 1979 growing seasons. Early blight epidemics that developed on plants sprayed according to a FAST-generated schedule were compared with early blight epidemics that developed on plants sprayed according to the following schedules: 7-day (7D) in both years, 14-day (14D) in 1978, and a no-spray check (0D) in both years. One cultivar was used in 1978, whereas four were used in 1979. The 7D treatment rows were sprayed nine times in each year, 14D treatment rows were sprayed five times, and the FAST treatment rows received only two and five sprays in 1978 and 1979, respectively. Analysis of variance indicated no cultivar × spray schedule interaction for either final disease severity or infection rate. There were no significant differences in disease severity or infection rates for the FAST and the more frequent spray schedules; the amount of disease resulting in the check plots was, however, significantly (P = 0.05) different from the other treatment plots. In summary, FAST produced a spray schedule that resulted in efficient and reliable early blight control.