News from the USDA Agricultural Research Service
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.
How the gall wasp arrived in Hawaii in April 2005 is unknown, but it quickly found suitable hosts on which to feed and reproduce, first on Oahu and then other Hawaiian islands
State officials are hoping to save Hawaii’s native wiliwili tree with a bug found in eastern Africa.
Mohsen Ramadan, a state exploratory entomologist, spent two months in Tanzania looking for a natural solution to fight the wiliwili-destroying Erythrina gall wasp and found a wasp of the Eurytoma species.
The Eurytoma wasps feeds externally on gall wasp larvae and pupae. It attacks 95 percent of gall wasps in Tanzania.
The gall wasp found its way to all of the main Hawaiian islands after being discovered on Oahu in April. Since then, it began ravaging the wiliwili, which is regularly used for landscaping, and the “tropic coral,” also known as “tall erythrina.”
Hawaii agriculture officials have been conducting tests on the Eurytoma species and to ensure it doesn’t pose threats to anything other than the gall wasp.
It could take up to a year for the testing to be completed and to obtain approval from state and federal agencies for permits to release the parasite.
State Department of Agriculture Plant Pest Control Branch biocontrol section officials are encouraged by what they’ve seen in lab tests of the Eurytoma wasp, which doesn’t have a name. The parasitoid produced its first generation in their lab last week, at the expense of gall wasps.
“If this proves to be specific,” Ramadan said, meaning there’s no threat other than to gall wasps, “it will save the wiliwili.”
The gall wasp is a new species, not only to Hawaii, but worldwide. Its presence was first documented three years ago in Taiwan, and in Singapore, Mauritius and Reunion in 2004, said state biocontrol section chief Kenneth Teramoto.
Teramoto said he thinks the pest may have arrived in Hawaii from Taiwan, which has a developing ornamental-plant industry.