Natural resistance of white spruce and the behavior of the eastern spruce budworm

A white spruce, Picea glauca (Moench) Voss. (pinaceae), plantation in southern Quebec contained two distinct types of trees: resistant and susceptible to attack by spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae). The primary purpose of this study was to evaluate if and how the pattern of feeding and oviposition preference are modified in response to past nutritional experience. Both lab-reared insects and field-reared insects, tested on artificial diet and foliage, respectively, failed to show differences in the pattern of feeding between groups with different nutritional experience. These findings suggest that the spruce budworm, like other specialists feeders, may not have evolved mechanisms of physiological or behavioral modification in response to previous nutritional stress. That being said, adult budworm, when reared on foliage from resistant trees, preferentially laid more eggs on foliage from susceptible trees but showed no significant preference when reared on foliage from susceptible trees. These findings illustrate that the presence of deterrent compounds on the surface of needles, coupled with larval experience, may be influencing adult oviposition preference. Both these findings have important implications for forest management strategies; plantations using mixed tree phenotypes may slow budworm adaptation to resistant trees