A black, two-millimeter-long wasp from East Africa is helping wage war on one of its own kind—the Erythrina gall wasp, an invasive species that’s decimated Hawaii’s endemic wiliwili (Erythrina sandwicensis) and introduced coral bean trees (Erythrina spp.).
Hawaii Department of Agriculture (HDOA) officials “recruited” the beneficial wasp, Eurytoma erythrinae, and first released it in November 2008 after evaluating its host specificity as a biocontrol agent. U.S. Department of Agriculture (USDA) entomologist Michael Gates’ scientific description and naming of the species, together with a collaborator, helped HDOA obtain the necessary federal approvals to make the release.
Female E. erythrinae wasps deposit their eggs inside galls where the pest larvae feed. Upon hatching, E. erythrinae larvae eat the gall wasp larvae. They pupate and emerge two weeks later as adults. The parasites don’t attack native wasps or other nontarget insects.
The HDOA found its “gall wasp gladiator” after dispatching two entomological teams to the pest’s native Africa in search of natural enemies, starting in spring 2006. In January 2007, Gates and Delvare were asked to identify the specimens collected based on their taxonomic expertise.
Gall-wasp parasitism has been as high as 70 percent at some release sites, but continued data collection will be necessary to correlate E. erythrinae’s rise to declines in tree damage.
Wasps wage war on behalf of Wiliwili trees