Release of Sphecophaga orientalis Donovan (Hymenoptera: Ichneumonidae: Cryptinae) in New Zealand as a possible ‘new association’ biocontrol agent for the adventive social wasps Vespula germanica (F.) and Vespula vulgaris (L.) (Hymenoptera: Vespidae: Vespinae).

Abstract

The hornet (Vespa spp.) parasitoid Sphecophaga orientalis Donovan was imported into New Zealand from Israel as a possible ‘new association’ biological control agent for the adventive pestiferous social wasps Vespula germanica (F.) the German wasp, and V. vulgaris (L.) the common wasp. In quarantine, when adult wasps were absent, S. orientalis propagated prolifically on sealed brood of both species of wasp. In the field, parasitoid cocoons were formed in four of eight German wasp nests inoculated with the parasitoid, but there was no attack on 27 inoculated nests of the common wasp. Whether S. orientalis has established is unknown. If worker common wasps prevent attack or remove developing parasitoid larvae from cells, it is possible that parasitoids may be able to successfully attack the small nests constructed by queens in spring, before workers emerge. A major decline in wasp populations over the release period may have decreased the likelihood of establishment because of fewer small spring-founded nests available for attack.