A study of habitat temperatures of the bark beetle Dendroctonus ponderosae hopkins in lodgepole pine

Abstract

Temperatures were measured at the bark surface and in the subcortical zone of Pinus contorta Douglas var. latifolia Engelm, infested by Dendroctonus ponderosae Hopkins, and compared with similar measurements in non-infested trees and with air temperatures. Subcortical temperatures were higher at night but usually lower during the day than air temperatures. Surface bark temperatures were intermediate. Temperatures were lower at the 1-ft. level than at higher levels. Highest subcortical temperatures occurred on the south aspect; daily maxima were later in the day and daily range was greater in infested than in non-infested trees, especially during the late stages of beetle brood development. Thin-bark trees had higher temperatures and less temperature lag than thick-bark trees. Temperatures were 5.5 to 7.5°C higher under maritime tropical than maritime polar air. The effects of temperature on various aspects of beetle behaviour, development and survival are discussed. Approximately 8,340 degree-hours above 10°C were required in the subcortical zone for the beetle to develop from egg to teneral adult.