Distribution and Abundance of Early Instar Gypsy Moth (Lepidoptera: Lymantriidae) in Forests During Day and Night

Studies were conducted to determine the distribution and abundance of early instar gypsy moth, Lymantria dispar (L.), within canopies of codominant Quercus rubra L., Q. alba L., and Q. prinus L. in moderate and dense populations during the day; and to compare the distribution and abundance of early instar gypsy moth within canopies of Q. rubra trees, saplings, and seedlings, and saplings of witch hazel, Hamamelis virginiana L., during day and night in a moderate population. Most larvae were observed in the lower canopy of codominant trees in all sites during the day. Variation associated with tree species was not significant at any site. Larval abundance was highly correlated, r 2 = 0.992, with preseason egg mass density. No differences in larval abundance or distribution were detected during day and night. More than 80% of all larvae were observed in the lower canopy, understory, and forest floor day and night. The most larvae per 1,000 leaves were detected on seedlings and the least in the upper canopy of codominant trees. The target for the aerial application of insecticides and release of parasitoids occupies a lower vertical position in the forest than was previously thought.