Data on the distribution of overwintering jack pine budworm (Choristoneura pinus pinus Free.) collected between 1985 and 1987 in northern Ontario are used to develop guidelines for sampling this stage of the budworm. Two alternative methods of expressing budworm density are considered: counting the number of budworms per metre of branch and counting the number per square metre of branch bark surface area. Estimates of budworm density for three levels in the tree’s crown are given for 4 site-years.
Entire branches are recommended as the sample units as the use of 60-cm branch-tip sections resulted in consistent underestimation of actual density per branch. Jack pine budworm density did not vary among cardinal compass directions and was generally highest at mid-crown levels.
The distributions of two parasitoids, Apanteles fumiferanae Vier. and Glypta fumiferanae (Vier.), which overwinter as an egg or first-instar larva within the jack pine budworm, also were considered. Apanteles was the most abundant parasitoid at all crown levels at all sites examined. Percentage parasitism by Apanteles was highest and that by Glypta was lowest on the branch-tip sections in relation to the branch-basal section, but total percentage parasitism was relatively constant over the entire branch, throughout the tree crown, and from tree to tree. Consequently, the sampling method for jack pine budworm is easily extended for estimating the rate of parasitism and therefore for providing a prediction of mortality that results from these two common parasitoids.