Parasitoids of Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae) recovered in western North America and first record of its egg parasitoid Gryon pennsylvanicum (Ashmead) (Hymenoptera: Platygastridae) in California

Abstract

The parasitoid complex of the western conifer seed bug, Leptoglossus occidentalis, was studied in British Columbia and California on Pinus monticola and P. contorta var. latifolia. Three egg-parasitoid species were identified: Gryon pennsylvanicum (Hymenoptera: Platygastridae), Ooencyrtus johnsoni (Hymenoptera: Encyrtidae) and Anastatus pearsalli (Hymenoptera: Eupelmidae). Leptoglossus occidentalis represents a new host record for O. johnsoni, and California is a new distribution record for G. pennsylvanicum. Gryon pennsylvanicum was the dominant species during the entire oviposition period of the bug, reaching peak parasitization levels in July (25%). Ooencyrtus johnsoni and A. pearsalli emerged only from eggs collected on Pinus monticola. The parasitization level by G. pennsylvanicum recorded on the two different Pinaceae hosts did not show any statistically significant difference. No tachinid eggs or exit holes by tachinid larvae were observed in any adult L. occidentalis collected in either British Columbia or California. The data collected encouraged the introduction of G. pennsylvanicum in Italy where L. occidentalis has become a serious pest. Laboratory host range assessment with this Platygastridae, in preparation for its field release in Italy, has already started.