Gypsy Moth Faces Renewed Challenge from Long-lost WaspBy Jim De Quattro
November 21, 1996
NEWARK, Del., Nov. 21--The surprise reappearance of a long-lost insect friend has spurred U.S. Department of Agriculture researchers to renew their abandoned effort to see if the insect, a small, harmless wasp from India, could help rein in the destructive gypsy moth.
Gypsy moth caterpillars are the worst insect scourge of forest and shade trees in the Eastern United States.
To help combat gypsy moths in the future, scientists with USDA's Agricultural Research Service are rearing thousands of Rogas indiscretus [ROW-goss in-dis-KREE- tuss] wasps from a couple of hundred collected this summer in India. The first test releases of this wasp in the U.S. since 1977 may be made next year, said Roger Fuester, research leader at ARS' Beneficial Insects Introduction Research Laboratory in Newark, Del.Were rearing as many Rogas wasps as possible for releases next May or June, probably in the Great Lakes region, Fuester said. So far weve reared about 3,000 to the cocoon stage. Well keep them refrigerated until just before their release. "Scientists had all but given up on this wasp," he said. "More than 30,000 were released from 1968 to 1977 in the Northeast and Mid-Atlantic, but no offspring were ever found."
Then, in 1994--the final year of a 20-year survey for gypsy moth natural enemies in 20 Maryland woodlots--nine Rogas cocoons showed up. ARS entomologists Robert F.W. Schroder and Ann M. Sidor found the cocoons about 25 miles south of their home base, the Insect Biocontrol Laboratory of ARS' Beltsville (Md.) Agricultural Research Center.
Fuester said the cocoons "tell us that Rogas has managed to survive and reproduce in this country, so we're going to try again to deploy it against the gypsy moth." Originally from Europe, the moth infests a region from New England west to Michigan and south to North Carolina, he said.
Among the first in line for wasps from Fuester's lab is entomologist Richard Reardon with USDA's Forest Service in Morgantown, W.Va. He described and named the species R. indiscretus, and made the first releases way back in 1968. "I'm excited that Rogas turned up after all these years," he said. "I plan to release the wasps in a range of environments in Maryland and Pennsylvania."
Honey-colored Rogas wasps are about 1/4 inch long. In spring, the female stings a caterpillar and deposits an egg inside it. After it hatches, the worm-like wasp larva devours the pest's insides. The larva spins a cocoon within the mummified caterpillar, and a few weeks later the adult wasp emerges. An adult female wasp can lay more than 200 eggs. The wasps do not sting animals or people.
In Maryland, Schroder and Sidor found the Rogas cocoons inside tussock moth caterpillars trapped in burlap strips wrapped around trees. Tussock moth species native to North America are considered minor pests of trees such as oak, aspen and alder. "A female Rogas wasp prefers gypsy moth caterpillars for egg laying, but if none is available she will settle for second-best, such as the dark tussock moth," Schroder said. This insect's scientific name is Dasychira basiflava [dassy-SHEER-uh bossy-FLAY-vuh]."Now that the biocontrol community knows Rogas is here," Schroder added, "I expect more will be found, and in gypsy moths. This may encourage biocontrol workers to check out one more tree, turn over one more leaf to see if Rogas or other imported enemies of gypsy moths are actually helping hold down gypsy moth populations."
Since 1960, ARS and cooperating scientists have imported and test-released more than 50 species of natural enemies of the gypsy moth. About a dozen species made new homes in this country, Schroder said. The Rogas wasps shipped from India were collected by G. Ramaseshiah, a scientist with India's Commonwealth Institute of Biocontrol. His expedition was funded by three USDA agencies: ARS, the Forest Service and the Foreign Agricultural Service.
Scientific contact: Roger W. Fuester, research leader, ARS Beneficial Insects Introduction Research Laboratory, Newark, Del. 19713, phone (302) 731-7330; Robert F.W. Schroder (e- mail email@example.com) and Ann M. Sidor, entomologists, ARS Insect Biocontrol Laboratory, Beltsville, Md. 20705, phone (301) 504-8369; and Richard Reardon, Forest Health Technology Enterprise Team, Forest Service, USDA, Morgantown, W.Va. 26505, phone (304) 285-1566.