DISTRIBUTION OF HYLOBIUS-PALES AND PISSODES-NEMORENSIS (COLEOPTERA, CURCULIONIDAE) WITHIN CHRISTMAS TREE PLANTATIONS WITH PROCERUM ROOT DISEASE

Procerum root disease caused by Leptographium procerum (Kendrick) Wingfield is the most serious disease problem facing Virginia Christmas tree growers producing eastern white pine, Pinus strobus L. Studies have shown an association between procerum root disease-affected trees and insect infestations, and L. procerum has been recovered from field-collected insects. To determine the species and spatial distribution within Christmas tree plantations, potential insect vectors were collected weekly, April-September 1988-1991, from plots containing baited pitfall traps. Plots were located in plantations with procerum root disease, plantations without procerum root disease, in forested areas outside both types of plantations, and in an urban setting. Trees within the plots were inspected for development of procerum root disease. Insects recovered included two weevil species, Hylobius pales (Herbst) and Pissodes nemorensis Germar, and bark beetles from the genera Ips De Geer, Pityophthorus Eichoff, Pityogenes Bedel, Orthotomicus Ferrari, and Xyleborus Eichoff. In plantations with procerum root disease, there were significantly more (P < 0.05) H. pales than P. nemorensis, and significantly more H. pales were contaminated with L. procerum. In plantations where procerum root disease was absent, there was no significant difference between the numbers of either weevil species or proportions contaminated with the fungus. Within the plots with procerum root disease, 27% of the trees developed symptoms of the disease during 3 yr of observation, but no trees developed disease symptoms in the asymptomatic plots.