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First Report of Naemacyclus fimbriatus Infecting Pitch Pine (Pinus rigida)

This is the first report of Naemacyclus fimbriatus (Schwein.) DiCosmo, Peredo & Minter (Rhytismatales) on Pinus rigida, and the first observation of this fungus infecting living needles. N. fimbriatus is known to occur on cone scales of P. brucia, P. halepensis, P. nigra, P. resinosa, and P. sylvestris, as well as fallen needles of P. maritima and P. pinaster, in Europe and North America (1). In September 1997, chlorotic and necrotic second- and third-year needles of pitch pine were observed to have ascomata fruiting bodies that were amphigenous, dark brown to black, immersed to erumpent, circular to subcircular, and 200 to 500 × 150 to 250 μm in size. Asci were club-shaped, eight-spored, and 83 to 98× 8.9 to 9.7 μm. Mature ascospores were phragmo-scolecosporous, 7-septate, and 78 to 91 × 2 to 2.5 μm. From these symptomatic needles, N. fimbriatus was frequently (>70%) isolated on 2% malt agar. In October 1997, fruiting bodies were also observed on dead fallen cones. During the autumn, the fungus produced 1 to 3 brown mycelial cords, 50 to 100 μm in diameter, which grew throughout the litter from the ascomata. The nature of the cords is still unknown. Pitch pine is rare in Québec, and this northernmost population is located about 10 km north of New York State, in the St. Lawrence Valley of Québec. We found that pitch pine was colonized by the fungus in a wide range of edaphic conditions, but more frequently on dry rock outcrops. We believe that unfavorable conditions such as the more than 200 days with frost and thin organic or mineral soil layer may predispose pitch pine to infection by this fungus.

Reference: (1) F. Di Cosmo et al. Mycotaxon 21:1, 1984.