Spathius agrili

Description

Spathius agrili is a parasitic non-stinging wasp of family Braconidae which is native to North Asia. It is a parasitoid of the emerald ash borer (Agrilus planipennis Fairmaire), an invasive species which has destroyed tens of millions of ash trees in its introduced range in North America. As part of the campaign against the emerald ash borer (EAB), American scientists in conjunction with the Chinese Academy of Forestry began searching in 2003 for its natural enemies in the wild, leading to the discovery of several parasitoid wasp species, including Spathius agrili. S. agrili was discovered in Tianjin, China where it is a prevalent prevalent parasitoid of EAB larvae in stands of an introduced ash species (Fraxinus velutina), and an endemic ash species ( Fraxinus mandshurica). S. agrili has been recorded to attack and kill up to 90 percent of EAB larvae. This wasp is a gregarious ectoparasitoid, meaning it lays multiple eggs on the surface of its host, and the larva feed externally. The life cycle of S. agrili was found to be synchronized with that of its preferred host stages - the emergence of adult wasps took place when third and fourth-instar larvae of EAB were available. The female wasps oviposit through the tree bark, paralyze the host larva and lay a clutch of eggs on the integument. The eggs hatch and the wasp larvae feed on the paralyzed host. When the larvae mature, they spin a cocoon and pupate within the host gallery. Spathuis overwinter as pupae within their cocoons under the bark of ash trees and emerge as adults in the summer.