Patterns of Gall Formation by the Cooley Spruce Gall Adelgid on Colorado Blue Spruce    (View PDF)

Whitney S. Cranshaw

Abstract: Observations were made of galling patterns by the Cooley spruce gall adelgid (Adelges cooleyi) on landscape and nursery plantings of Colorado blue spruce from 1985-1988. Overall incidence of galling varied widely between seasons, and appeared to be related to late winter and early spring weather conditions. Strong orientation of galls occurred with highest numbers of galls occurring along the north (37%) and east (34%) sides of the trees. Galling was also found to be consistently correlated on individual trees, suggesting a possible genetic basis for resistance. Galling was associated with tree color, being greatest on trees with greener coloration, but was not correlated with onset of spring bud break. The implication of these findings in tree siting and in identifying resistant genotypes is discussed.

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https://doi.org/10.48044/jauf.1989.059