Oviposition and Pupal Survival of Gypsy Moth (Lepidoptera: Lymantriidae) in Virginia and North Carolina Pine-Hardwood Forests

Abstract

Gypsy moth, Lymantria dispar L., oviposition and pupal survival were examined within mixed pine-hardwood stands located in the Virginia and North Carolina coastal plain and the North Carolina piedmont. Where burlap bands were not present as barriers to larval dispersal, the percentage of loblolly pine with gypsy moth egg masses present was significantly greater than expected if oviposition occurred randomly. The loblolly pine and oak components of the forests also had more total egg masses per tree compared with the other tree genera or species. However, when adjusted for tree size, egg mass density was generally similar among tree groups within an infestation. Tree size (dbh) was positively correlated with the number of egg masses present on a tree. Pupal predation, measured using freeze-dried pupae, was significantly higher over the 5-d sample period for (1) females versus males, (2) pupae placed at 0 m on the tree bole versus at 2 m, and (3) pupae placed on oak versus pine. The differential predation on oak versus pine appears to be the result of heavier vertebrate predation of the pupae placed on oak. The high rate of pupal removal, beginning the first night of exposure, from all locations suggests that predators will not have to learn to accept gypsy moth in their diets. The higher survival of pupae on pine is suggested to be one of the factors influencing the high egg-mass density on pine. Implications of these results for gypsy moth population dynamics in southern pine-hardwood forests are discussed.