To our knowledge, this is the first report of Cryptocline taxicola (Allesch.) Petrak (Coelomycetes) on Pacific yew (Taxus brevifolia Nuttall) and the first observation of the fungus infecting living needles. C. taxicola is known to occur on needles of Taxus baccata in Europe (on T. baccata var. fastigiata) and North America (Vermont) (on T. baccata var. canadensis) (2). In August 1999 and 2000, chlorotic and necrotic current and second-year needles of Pacific yew were observed to have fruiting bodies, sometimes greater than 400 per needle, on the upper surface. Acervuli were circular to subcircular, yellowish, surrounded by brown circles, subcuticular to intraepidermal, at first covered, later exposed by the fissure of the cuticule, and 150 to 350 μm wide. Hyphae in host tissue were septate, brownish, and 3 to 4.5 μm in diameter. Conidiophores were phialidic, cylindrical, hyaline, 10 to 20 × 2.5 to 4.5 μm. Mature conidia were ellipsoidal to oval, truncate at the base, obtuse at the apex, hyaline to slightly pigmented, 8 to 17 × 4 to 5 μm. From these symptomatic needles, C. taxicola was often isolated (>85%) on potato dextrose agar. Koch's postulates were completed for C. taxicola by spraying current-year living needles, on one twig of each of separate plants (five) of T. brevifolia with a conidial suspension of 4 × 103 conidia per ml. Five control twigs were sprayed with sterile, distilled water. Twigs were covered with black sterile plastic bags and incubated outdoors for 24 h, when the bags were removed. Within 3 weeks, inoculated needles exhibited chlorotic and necrotic symptoms similar to those originally observed, but symptoms were never observed on control twigs. The fungus was reisolated (91%) only from the symptomatic needles. T. brevifolia trees growing in the Montreal Botanical Garden (Quebec, Canada) are clones originating from the Pacific Coast of the United States. We found that Pacific yew was colonized more frequently on the dry rock outcrops in the Alpine and Chinese Garden tree plantations. We believe that inappropriate stand selection, unfavorable humid conditions, and a thin organic soil layer may predispose Pacific yew to infection by this fungal species. A similar effect has been reported in Europe (1) for Cryptocline pseudotsugae causing serious levels of disease in a Pseudotsuga menziesii plantations.
References: (1) T. L. Cech. Forstschutz Aktuell. 25:13, 2000. (2) G. Morgan-Jones. Can. J. Bot. 51:309, 1973.
