Influence of Parasites on Two Populations of Choristoneura pinus(Lepidoptera: Tortricidae) in Michigan1

Abstract

Parasites were reared from the eggs, early larvae, late larvae, and pupae of the jack-pine budworm, Choristoneurapinus Freeman. Host collections were made from the mid- and lower crown of 10 jack pine trees in each of 2 counties in Michigan for 2 generations of the budworm. Apparent parasitism by species, crown level, area, and stage of the host was determined. Twenty-six species of primary parasites and 4 species of hyperparasites were reared from the budworm. Nine species are new records for this host. The largest amount of parasitism occurred in the early larval stages and was attributed predominantly to 2 species, Apanteles fumiferanae Viereck and Glypta fumiferanae (Viereck). Mortality caused by them varied from 1.3 to 51.3%, and it was greatest at midcrown. Late-stage parasitism of budworm larvae was variable. Five species of tachinid flies accounted for most of this parasitism. The maximum parasitism obtained by this group was 17.9%. Itoplectis conquisitor (Say) was the most important parasite of budworm pupae; it killed as much as 24.5% of the pupae in 1 sample. The proportion of total mortality in a generation of C. pinus attributable to parasites of larvae and pupae was low and variable, ranging from 0.4 to 8.5%. Dirophanes banksianae Allen is reported to be a new synonym of Phacogenes hariolus (Cresson).