Enemy of isle wiliwili trees defeated by African import

Question: Whatever happened to that tiny alien wasp that began attacking native wiliwili trees in 2005? At the time there were dire predictions about the state’s wiliwili trees being wiped out.

Answer: There were indeed fears that the newcomer Erythrina gall wasp, an insect the size of a grain of sand, would kill off native wiliwili and other coral trees in Hawaii. Some conservationists were so alarmed by the rapid spread of the pest that they were collecting wiliwili seeds just in case the ancient low dryland forest tree became extinct.

How important is the wiliwili tree in Hawaii?

The wiliwili is mentioned in the "Kumulipo," the ancient creation chant, and is used in Hawaiian tradition to craft surfboards, canoe outriggers and fish net floats. Both the wiliwili and tropic coral trees are used for landscaping, soil and water conservation and as noise and windbreaks.

The tiny wasp, first discovered in Manoa, wreaks its havoc after imbedding its larvae in the leaf tissue. It doesn’t take long before leaves and stems lose their vigor in what often can be a death sentence.

This was happening to wiliwili and coral trees across the islands, and hundreds of trees were killed until 2008. That’s when the state Department of Agriculture called on another small wasp — Eurytoma erythrinae — to battle the pest.

The gall wasp predator was discovered by entomologists who were sent to Africa in search of a natural enemy that would attack only the gall wasp and no other species in Hawaii.

The new wasp, about twice the size of the gall wasp, was released on all of the main Hawaiian Islands. After 2009 rain, wiliwili trees across the state began sprouting fresh, healthy leaves. And the wiliwili and corals continue to make their comeback, said Mohsen Ramadan, entomologist with the state Department of Agriculture.

"The parasite is doing a very good job," Ramadan said.

Just in case there’s any hitch, state officials are testing a second parasite that was brought back from Africa, he said. It will be released if the Eurytoma erythrinae wasp fails to continue keeping the gall wasp in check.

———
This update was written by Timothy Hurley. Suggest a topic for “Whatever Happened To …” by writing Honolulu Star-Advertiser, 500 Ala Moana Blvd., Suite 7-210, Honolulu 96813; call 529-4747; or email cityeditors@staradvertiser.com.