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Orient Express for wasps.

Orient Express for Wasps

Rural China was the starting line for thousands of beneficial wasps that disembarked at Newark, Delaware, in the summer of 1990. ARS scientists recruited the tiny insects to battle the apple ermine moth--a pest that threatens Washington apples.

Entomologist Robert W. Pemberton and colleagues collected the wasps, known as Ageniaspis fuscicollis.

Pemberton, director of the ARS Asian Parasite Laboratory in South Korea, says Chinese villagers were puzzled and amused that strangers would venture to their province to look for insects in trees.

"In one village," he remembers, "we were checking apple trees next to a school playground. Suddenly we were surrounded by laughing, excited children. We soon learned that most of them had never seen a Caucasian before."

From Chinese apple orchards and lone trees, Pemberton gathered dry, mummified remains of ermine moth caterpillars. Hidden inside each stiff grey caterpillar corpse were immature A. fuscicollis wasps.

Earlier, female wasps had laid their aggs inside ermine moth eggs. The moth eggs hatched into small caterpillars. But the caterpillars were doomed because each wasp egg had become a chain of embryos that eventually formed about 50 to 135 young wasps. The wasps fed on the unlucky caterpillar, killing it.

The scientist found the moth mummies in sticky webs woven at twig junctions and between branches.

"The webs feel something like cotton candy," says Pemberton. "In China, we spent nights working in our rooms, sorting mummies from the webbing."

In June and July of 1990, Pemberton air-freighted 3,500 mummies to ARS colleagues in Newark. When adult wasps emerged from the mummies, the Delaware scientists shipped them to entomologists such as Thomas R. Unruh at the ARS Fruit and Vegetable Insect Research Unit in Yakima, Washington. Unruh has released several promising natural enemies of the apple ermine moth in Washington. These include Ageniaspis wasps collected by ARS scientists in Europe as well as Asia.

In large numbers, ermine moth caterpillars can munch the leaves off an apple tree in about 6 weeks. The insect gets its name from its pale, silvery grey wings that resemble the coat of an ermine weasel.

The moths first appeared in this country on homeowners' apple trees in western Washington in 1985. Recently, the moths showed up east of the Cascades in the part of the state that's world famous for its apple orchards.

"We're hoping the wasps will suppress ermine moths on backyard trees and in abandoned orchards in western Washington," says Unruh. "If the wasps flourish, we'll share them with apple growers in eastern Washington."
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Title Annotation:Agricultural Research Service imports Ageniaspis fuscicollis to battle the apple ermine moth
Author:Corliss, Julie; Wood, Marcia
Publication:Agricultural Research
Date:Oct 1, 1991
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