Glyptapanteles flavicoxis (Hymenoptera: Braconidae) Dispersal in Relation to Parasitism of Gypsy Moth (Lepidoptera: Lymantriidae)

Abstract

Glyptapanteles flsavicoris Marsh is a recently imported but unestablished parasitoid of the gypsy moth, Lymantria dispar (L.). Its dispersal and parasitization was field-tested along distance gradients at high (5,307 egg masses/hal and low (750 masses/hal host density sites. Host larvae were collected in each 14.3-ha site after the last of eight parasitoid releases. Parasitism of 13.8% was recorded in 7.4 ha at the low density site, and 1.4% parasitism was recorded in 2.6 ha at the high density site. Parasitism was aggregated around the release point for each site. Each female parasitized an estimated 68 and 9 gypsy moth larvae at the low and high density sites, respectively. Parasitism in branch sleeve cages on beech and oak was higher at low host densities. In laboratory tests, the effects of female density (1, 2, 3) and exposure time (12, 24, 48 h) were tested at constant host density. G. flavicoris parasitization significantly increased with female density. Results suggest that future G. flavicoxis release points should be separated by at least 150 m and that most parasitism will occur near the point of release within 12 h. G. flavicoxis may be most successful against low-density gypsy moth populations such as pre-outbreak infestations rather than against epidemic populations.