Implications of spruce budworm (Lepidoptera: Tortricidae: Choristoneura fumiferana Clem.) management for the species diversity of moths, Lepidoptera, and carabid beetles (Coleoptera: Carabidae) in the Manitoba boreal forest
Wytrykush, Carla M.
The purpose of this study was to determine the implications of foliage protection measures as a spruce budworm management technique on the species diversity of moths and carabid beetles in the Manitoba boreal forest. This objective was addressed by comparing control sites not infested with spruce budworm, infested sprayed sites and infested unsprayed sites. A paired design of sprayed and unsprayed sites was used. Each pair of sites had a similar history of budworm infestation. An unpaired set of three control sites outside the area of infestation was also used. Treatment effects on the vegetation were assessed by quadrat sampling of the trees, shrubs and ground vegetation in each site. Light traps were used to collect moths, and pitfall traps for carabid beetles. Summary diversity and abundance statistics did not show strong effects of treatment. There was higher tree diversity in most unsprayed sites presumably because of the presence of deciduous tree species. Shrub diversity was higher in sprayed sites. There were more moths in most sprayed sites in 1996. Two carabid beetle species, 'Agonum retractum' LeConte, and ' Sphaeroderus nitidicollis brevoorti' LeConte, were more abundant in unsprayed sites, and this tended to lower carabid diversity in the unsprayed sites. Species composition, as reflected in ordination analysis, was more sensitive to treatments. The ordination of the vegetation data showed strong influences of treatment. The moth assemblage also showed responses to treatment and a close linkage to the vegetation patterns. The carabid beetle assemblage was not distinctly affected by the treatment imposed. It is concluded that the vegetation changes were the mechanism by which treatments influenced the insect assemblages, and that phytophagous insects were most influenced, because of their direct response to the vegetation assemblage.