Evaluation of an Electronic Apple Scab Predictor for Scheduling Fungicides with Curative Activity. M. A. Ellis, Associate Professor, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Ohio State University, Wooster 44691. L. V. Madden, Assistant Professor, and L. L. Wilson, Agricultural Technician I, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Ohio State University, Wooster 44691. Plant Dis. 68:1055-1057. Accepted for publication 8 May 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-1055.

A microcomputer for use in predicting primary apple scab infection periods was evaluated in Ohio during two growing seasons. The unit predicted 10 and 14 primary infection periods in 1982 and 1983, respectively. Bitertanol, fenarimol, etaconazole, and triforine applied at 72 hr and all fungicides except triforine applied at 96 hr after initiation of predicted infection periods provided excellent control. Captan provided excellent scab control when applied in a standard protectant spray program but was not effective when applied 72 hr after predicted infection periods. The apple scab predictor was as effective as the Mills system in predicting primary scab infection periods under Ohio conditions. Well-timed curative spray programs of bitertanol, fenarimol, etaconazole, and triforine were as effective as protective spray programs of captan and Dikar in controlling apple scab but were more efficient because three or four fewer sprays were used to achieve control.

Keyword(s): disease forecasting, ergosterol-inhibiting fungicides, Venturia inaequalis.