Susceptibility of European Hazelnut Clones to Eastern Filbert Blight. J. N. Pinkerton, Research Plant Pathologist, USDA-ARS, Horticultural Crops Research Laboratory, Corvallis, OR 97330. K. B. Johnson, S. A. Mehlenbacher, and J. W. Pscheidt. Assistant Professor, Department of Botany and Plant Pathology, Associate Professor, Department of Horticulture, and Assistant Professor, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331. Plant Dis. 77:261-266. Accepted for publication 10 November 1992. 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-77-0261.

In the springs of 1989 and 1990, 2- to 3-yr-old hazelnut trees representing 19 cultivars were exposed to ascospores of Anisogramma anomala, which causes eastern filbert blight. The trees were potted and randomly arranged under wire mesh platforms elevated 1.8 m from the ground. Diseased hazelnut branches were placed on top of the platforms in low, medium, or high numbers to provide three levels of inoculum. During periods of rain, ascospores of the pathogen were released from the diseased branches and deposited on the potted trees. External disease symptoms developed at 16 and 28 mo after initial exposure to inoculum, at which times disease responses were evaluated. Cultivars differed significantly in disease incidence, mortality, number of cankers per tree, proportion of wood cankered, and proportion of dead wood. The cultivars Hall’s Giant, Willamette, Casina, and Tonda di Giffoni had the lowest disease severities. Barcelona, Ennis, Butler, Daviana, and DuChilly, the predominant cultivars in Oregon, were rated as moderately to highly susceptible. Gasaway, an obsolete pollenizer, did not develop disease symptoms. Inoculum density did not affect the relative resistance rankings of the cultivars. In a second experiment beginning in 1990, 44 hazelnut clones (cultivars and selections) were exposed to a high dose of A. anomala ascospores. Five clones—Gasaway, Gem, Winkler, Giresun 54-21, and Giresun 54-56—failed to develop symptoms of eastern filbert blight. An additional 13 clones were more resistant than the widely grown cultivar Barcelona. The relative resistance rankings of the cultivars evaluated in both experiments were consistent between experiments.

Keyword(s): Corylus americana, C. avellana.