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Evaluation of Chlorothalonil, Fenarimol, and Flusilazole for Control of Eastern Filbert Blight. Kenneth B. Johnson, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331-2902. Jay W. Pscheidt, and John N. Pinkerton. Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331-2902; and USDA-ARS Horticultural Crops Research Laboratory, Corvallis, OR 97331. Plant Dis. 77:831-837. Accepted for publication 20 April 1993. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1993. DOI: 10.1094/PD-77-0831.

In a greenhouse experiment, treatment of 3-wk-old hazelnut (Corylus avellana) seedlings with suspensions of chlorothalonil (1.8 g a.i./L), fenarimol (0.038 g a.i./L), or flusilazole (0.030 g a.i./L) prior to inoculation with ascospores of Anisogramma anomala resulted in 4, 5, and 7% incidence of eastern filbert blight, respectively, compared to 53% in the inoculated control. In field experiments, exposure of 1- or 2-yr-old potted trees to natural releases of A. anomala ascospores demonstrated that hazelnut is susceptible to infection after vegetative budbreak, and that one to five applications of chlorothalonil, fenarimol, or flusilazole onto vegetative tissues that develop after budbreak significantly (P ? 0.05) reduced disease development. Eastern filbert blight was controlled completely when four or five fungicide applications were made beginning at vegetative budbreak in March and extended on a 23-wk schedule into May. The relative efficacy of chlorothalonil, a protectant fungicide, appeared to be independent of hazelnut phenology. In contrast, the efficacy of fenarimol, a locally systemic fungicide, may depend on the amount of vegetative tissue into which it can be absorbed.