Title: Pityophthorus orarius Bright (Coleoptera: Scolytidae) in a northern California Douglas-fir seed orchard: effect of clone, tree vigor, and cone crop on rate of attack
Author: Rappaport, Nancy G.; Wood, David L.
Source: Canadian Entomologist, Vol. 126: 1111-1118
Description: The geographic range of the Douglas-fir twig beetle, Pityophthorus orarius Bright, was extended beyond the original provenance of southern British Columbia to northern California. A survey of 457 Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] trees in 1985 revealed that those with heavy cone crops were more likely to be infested by twig beetles than were those with a light crop. Furthermore, attack rates differed among clones. A second survey done in 1987 confirmed the importance of clone and cone crop in attack rate. In this survey, stressed trees were attacked at a higher rate than unstressed trees. Beetle distributions appeared clumped in both surveys, possibly because of semiochemicals or oviposition behavior.
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Rappaport, Nancy G.; Wood, David L. 1994. Pityophthorus orarius Bright (Coleoptera: Scolytidae) in a northern California Douglas-fir seed orchard: effect of clone, tree vigor, and cone crop on rate of attack. Canadian Entomologist, Vol. 126: 1111-1118.