J. Juzwik, MORPHOLOGY, CULTURAL-CHARACTERISTICS, AND PATHOGENICITY OF RHIZOSPHAERA-KALKHOFFII ON PICEA SPP IN NORTHERN MINNESOTA AND WISCONSIN, Plant disease, 77(6), 1993, pp. 630-634
Morphology, cultural characteristics, and pathogenicity of Rhizosphaer
a kalkhoffii from spruce (Picea spp.) showing premature needle loss in
northern Minnesota and Wisconsin were investigated. Pycnidiospores fr
om needles, conidia of the Hormonema-like synanamorph, and pycnidiospo
res produced in culture were similar for Colorado blue, Engelmann, Nor
way, and white spruce collections and isolates. Pycnidiospores from bl
ack spruce needles were smaller than those from Colorado blue or white
spruce (P < 0.05). Colony diameters at 14 days were similar on four d
ifferent spruce needle extract agars for isolates from Colorado blue,
Engelmann, and white spruce. Growth profiles of the fungus from Colora
do blue, Engelmann, and white spruce on three agar media at five tempe
ratures, and in three liquid media at three temperatures, were also si
milar to each other, with optimum growth occurring at either 20 or 25
C. Needle cast symptoms and R. kalkhoffii pycnidia developed within 12
mo on black, Colorado blue, Norway, and white spruce after inoculatio
n with pycnidiospores of an isolate of the fungus from either Colorado
blue or white spruce.