EFFECTS OF OXIDANT AIR-POLLUTANTS ON WESTERN PINE-BEETLE (COLEOPTERA,SCOLYTIDAE) POPULATIONS IN SOUTHERN CALIFORNIA

The attack rates, brood survival, and emergence rates of the western p ine beetle, Dendroctonus brevicomis LeConte, and incidence of entomoph agus associates, were compared between photochemical oxidant damaged, and apparently healthy, ponderosa pine trees, Pinus ponderosa Dougl. e x Laws in the San Bernardino Forest in Southern California. The result s from this study suggest that oxinant-damaged trees attacked by weste rn pine beetle produced about the same total brood with lower initial attacks when compared with healthier trees, whereas the numbers of pre dators and parasitoids were higher in the healthier trees. This higher productivity trend for western pine beetle is most evident in trees a ttacked by the first beetle generation. Trees attacked by the second g eneration, both damaged and healthy, produced much less western pine b eetle brood than generation I attacked trees, regardless of oxidant da mage. The implication of these results is that, in stands with a highe r proportion of oxidant damaged trees, a given population of western p ine beetle could kill more trees, and increase at a greater rate, than in a stand with a lower proportion of damaged trees. (C) 1997 Elsevie r Science Ltd.