Survival of within-treeIps calligraphus [Col.: Scolytidae]: Effect of insect associates

Abstract

Mechanical exclusion methods were used on the preferred portion of the hosttree bole to evaluateIps calligraphus brood mortality caused by the insect associate complex with and without the contribution ofMonochamus sawyer foraging. The studies compared brood adultIps calligraphus emergence from beetle infested bolts from which all insect associates were excluded, from which onlyMonochamus sawyers were excluded, and those bolts which were exposed to all insect associates. The least mortality occurred in bolts from which all insect associates were excluded, significantly more mortality occurred in bolts from which only sawyers were excluded, and the greatest mortality occurred in bolts exposed to all insect associates. Average monthly mortality due to insect associates was 89%, with 51% due to sawyer foraging. Insect associates were found to be more effective from May through July, while sawyer foraging produced the greatest within-bolt mortality from August through October.