Gypsy Moth Faces Renewed
Challenge from Long-lost Wasp
By 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 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
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
"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.