Predator wasp released to save wiliwili trees
State Department of Agriculture exploratory entomologist Mohsen Ramadan was absent but the product of his work was present in the release of 500 tiny wasps called Eurytoma erythinae into a stand of native wiliwili trees at Lili'uokalani Botanical Gardens in Liliha.
The insects, one-quarter size of a mosquito, are natural enemies of the Erythrina Gall Wasp, which has been devastating wiliwili and coral trees statewide since 2005 and worldwide from 2004..
Ramadan, a native of Egypt who has been working for the the Agriculture Department since 1997, went to Tanzania in 2005 and 2007 to find a natural enemy for the gall wasp because the country had more than 15 species of Erythrina, which include native wiliwili and other introduced local species such as coral trees and the tall erythrina that are widely used as windbreaks.
He found a predator that feeds externally on gall wasp larvae and pupae and brought it back to Honolulu in 2006. At the time, Ramadan told The Advertiser, "I'm very excited about this parasitoid because it attacks 95 percent of the gall wasps in Tanzania."
A team from the University of Hawai'i College of Tropical Agriculture and Human Resources also traveled to Africa to aid in the search.
Ramadan is in Africa searching for two more predator wasps and also for control solutions to invasive weeds such as fireweed, fountain grass and Ivy gourd, said Janelle Saneishi of the Department of Agriculture
Permits to release the bio-control insects were obtained from the statei Department of Agriculture in 2007, and the permit from the U.S. Department of Agriculture about a week ago.
The state yesterday released Eurytoma erythinae as a biological control agent in the first of 12 planned releases statewide. Fifteen minutes after the release, Plant Pest Control Branch officials observed the predator laying eggs on the leaves of the wiliwili, where gall wasps lay larvae.
The gall wasp larvae cause severe galling or deformities which will result in the leaves dropping off. Without its leaves, the wiliwili is not able to derive much energy and will eventually decline in health and die, officials said.
"The release of this natural predator of the erythrina gall wasp is the only lifeline for our native wiliwili trees," said Sandra Lee Kunimoto, chairperson of the Hawai'i Board of Agriculture. "Finding this biological control agent and making sure that it will not cause harm to other plants or beneficial insects in Hawai'i has been a priority for our staff since the discovery of the gall wasp here in 2005."
Biological control is the only way to save the wiliwili in remote and forested areas, said Neil Reimer, manager of the Plant Pest Control Branch.
"This is actually the perfect time to release this bio-control because the young leaves are just emerging and as the gall wasp population increases, so will the predatory wasps," Reimer said.
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