Evaluation of an Electronic Apple Scab Predictor for Scheduling Fungicides with Curative Activity

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Abstract
A microcomputer for use in predicting primary apple scab [Venturia inaequalis] infection periods was evaluated in Ohio [USA] during 2 growing seasons. The unit predicted 10 and 14 primary infection periods in 1982 and 1983, respectively. Bitertanol, fenarimol, etaconazole and triforine applied at 72 h and all fungicides except triforine applied at 96 h 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 h 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 3 or 4 fewer sprays were used to achieve control.