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Disease Control and Pest Management

Detection of Cytospora Species in Twig Elements of Peach and its Relation to the Incidence of Perennial Canker. D. J. Royse, Graduate Research Assistant, Department of Plant Pathology, University of Illinois, Urbana, IL 61801, Present address of senior author: Department of Plant Pathology, Pennsylvania State University, University Park, PA 16802; S. M. Ries, Assistant Professor, Department of Plant Pathology, University of Illinois, Urbana, IL 61801. Phytopathology 68:663-667. Accepted for publication 3 October 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-663.

Nontreated and captafol- or benomyl-treated twig elements (buds, leaf scars, and internodes) of field-grown Redhaven peach trees were monitored at 2- to 3-wk intervals to detect increases in the occurrence of Cytospora spp. during the infection period from November to April. There was no significant effect of fungicides on the number of isolations of Cytospora spp. from twig elements until late winter. The infection rate (IR) was reduced more by captafol than by benomyl. Applications of captafol during leaf fall or during late winter 1976-1977 significantly reduced canker incidence in the spring of 1977. Benomyl applied at time of leaf fall or late-winter 1976-1977 was effective in reducing canker incidence in the spring of 1977. Benomyl applied at leaf fall in 1975, however, was not effective in reducing the disease in the spring of 1976. Simple correlation coefficients (r) were higher between leaf-scar isolations and canker incidence than between bud or internode isolations and canker incidence at two dates in 1977 (bud break and 10 days after bud break). The contribution of the leaf-scar element to the incremental proportions of variance (ΔR2) values for canker incidence always was higher than that of other twig elements at bud break and 10 days after bud break. Leaf-scar isolations had higher ΔR2 values in canker incidence at bud break than 10 days after bud break. Bud isolations produced higher ΔR2 values in canker incidence 10 days after bud break than at bud break.

Additional keywords: Cytospora cincta, C. leucostoma, multiple regression methods, Valsa spp.