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Etiology

Etiology, Symptomology, Epidemiology, and Control of Naemacyclus Needlecast of Scotch Pine. B. R. Kistler, Research Assistant, Department of Plant Pathology, The Pennsylvania State University, University Park, PA 16802; W. Merrill, professor, Department of Plant Pathology, The Pennsylvania State University, University Park, PA 16802. Phytopathology 68:267-271. Accepted for publication 29 August 1977. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-267.

Naemacyclus minor is a primary parasite of Scotch pine; it causes needlecast in Pennsylvania Christmas tree plantations. The current year’s needles are infected in mid-July and August, and again in November. Viable ascospores are present throughout the year and infection may occur at any time environmental conditions are favorable. Symptoms develop in September and October after a 10- to 15-mo incubation period. Infected needles become yellow with prominent, transverse brown bars. These needles are cast during October and November, and the characteristic waxy-tan apothecia then form on them. Optimum temperatures for mycelial growth and development of apothecia in vitro are 25 C and 21 C, respectively. Infection was significantly reduced by Manzate 200 applied [1.7 kg/ha in 939 liters of water (= 1.5 lb/100 gal/acre)] in October and November.