500 wasps released to save isle wiliwili
POSTED: Wednesday, November 26, 2008
|This story has been corrected. See below.|
A natural battle between "good" and "bad" wasp species may save the wiliwili and coral trees in Hawaii.
Yesterday, state Department of Agriculture officials released the first 500 tiny wasps called eurytoma erythrinae at Liliuokalani Botanical Gardens in Liliha. More releases are planned on Oahu and the neighbor islands.
The insects were brought from Africa to prey on the erythrina gall wasp, which has been devastating Hawaii's wiliwili trees since 2005.
About the wiliwili tree:
» The tree is endemic to Hawaii but is part of a family of trees also found in other tropical and subtropical parts of the world.
About the newly introduced Eurytoma erythrinae:
» The species' larvae feeds on the Gall Wasp's larvae, circumventing the feast on wiliwili trees.
» Its average size is 1.5 millimeters for males, 2.1 millimeters for females.
» It was collected from Masai Camp, Arusha Region, Tanzania, on Jan. 27, 2006.
The tree killer
About the Erythrina Gall Wasp:
» It inserts its eggs into young leaves of erythrina trees like the wiliwili, causing the leaves to die. Without leaves, the trees die.
» The species was discovered in 2004 and is believed to originate in East Africa.
» It has spread to Hong Kong, China, India, Thailand, Okinawa, the Philippines, Guam and American Samoa.
Sources: Department of Agriculture and Wikipedia
A life and death struggle at the insect level is now underway and it could be very important for Hawaii's besieged Wiliwili trees.
"The release of this natural predator of the erythrina gall wasp is the only lifeline for our native wiliwili trees," said Sandra Lee Kunimoto, director of the state Department of Agriculture. "Finding this biological control agent and making sure that it will not cause harm to other plants or beneficial insects in Hawaii has been a priority for our staff since the discovery of the gall wasp here in 2005."
State agriculture officials are confident that introducing the insect to Hawaii won't have any "unintended consequences," like the 19th-century introduction of mongooses to control rats. Mongooses are day creatures, while rats roam at night, and their paths never crossed.
"Our research shows it is very host-specific," said Neil Reimer, plant pest control manager. "It doesn't feed on anything else we tested it on."
The gall wasp was first detected in Manoa in April 2005 by a University of Hawaii researcher.
It lays eggs in the leaves of erythrina trees like the wiliwili. The larvae cause severe galling or deformities in the leaves, which drop off as a result. Without its leaves, the tree declines in health and dies.
The city had to remove about 1,000 nonnative wiliwili trees, which cost about $600,000. The cost for replacing those trees could reach into the millions, city officials have said.
The native wiliwili trees fare better because they drop leaves in the summer, but they remained threatened by the gall wasp.
The new insect lays its eggs next to the gall wasp eggs. When the larvae emerge, the biocontrol wasp larvae preys on the gall wasp larvae.
Less than an hour after the release yesterday, the Eurytoma erythrinae already began laying eggs.
The state's exploratory entomologist, Mohsen Ramada, collected the newly introduced wasp from its native Tanzania, not far from the slopes of Mount Kilimanjaro. The wiliwili tree also has origins in Tanzania.
Ramada is currently in Africa collecting potential biocontrol agents for invasive weeds like fireweed, fountain grass and ivy gourd.
The federal permit to release the Eurytoma erythrinae was obtained from the U.S. Department of Agriculture last week.
Scientific studies and observations will be conducted every month to ensure all is going according to plan.
"This is actually the perfect time to release this biocontrol, because the young leaves are just emerging and as the gall wasp population increases, so will the predatory wasps," Reimer said.