Infection Periods in Naemacyclus Needlecast of Scots Pine. W. Merrill, Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. B. R. Kistler, former Research Assistant, L. Zang, Research Assistant, and K. Bowen, Undergraduate Student, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Plant Dis. 64:759-761. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-759.

Isolations from 5 yr of complements of Scots pine needles from needle emergence from the fascicle sheath until casting 16–18 mo later showed three infection periods by Naemacyclus minor. Period one extended from the time of full needle elongation (about mid-July) until late August, period two from early November to early December, and period three from mid-April until late August of the following year. During 5 yr of study, periods one and three were periods of major infection, with greatest infection occurring in period three. Increase in level of infection during period two usually was not significant, although fruit body formation was most conspicuous at this time. The incubation period varied from 2 to 16 mo, depending on when the needles were infected.