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Two decades of persistence by ARS scientists have renewed attempts to
establish a small Asian wasp--a natural enemy of gypsy
moths--in the United States. Gypsy moth caterpillars are the worst
insect pests of forest and shade trees in the East. But after an egg of
a Rogas indiscretus wasp hatches inside the caterpillar, the young
wasp eats the pest's insides. One female wasp can lay 200 or more eggs.
From 1968 to 1977, scientists released about 30,000 Rogas wasps that
all
seemed to vanish. But in 1994, the last year of a 20-year monitoring study,
ARS researchers in Maryland found several Rogas cocoons. Their discovery
led to the first new Rogas shipment in decades--about 200 cocoons collected
last June in India and shipped to an ARS lab in Delaware. There, several
thousand wasps will be reared for releases planned in Maryland, Michigan
and Pennsylvania in 1997. Gypsy moths, originally from Europe, have spread
to occupy a region from New England west to Michigan and south to North
Carolina. ARS and cooperating scientists have imported and test-released
more than 50 natural enemies of the moth. About a dozen are known to have
become established. Others may be here but, like Rogas, have so far eluded
detection.
Insect Biocontrol Laboratory,
Beltsville, MD
Robert F.W. Schroder/Ann M. Sidor, (301) 504-8369
Beneficial Insects Introduction Research Laboratory, Newark, DE
Roger W. Fuester, (302) 731-7330
"Seeding" predatory beetles in wooded areas could help
rein in gypsy moths, according to scientists who conducted field tests in
three states. One Calosoma sycophanta beetle, also known as the caterpillar
hunter, can eat as many as 150 gypsy moth caterpillars. Early in this
century, imported Calosoma beetles were released in New England. But their
natural spread has lagged behind that of the gypsy moth. To test a different
strategy, scientists in 1994 released about 100 caterpillar hunters at each
of five plots in Delaware, Michigan and West Virginia. The beetles didn't
go hungry: The species reproduces only if gypsy moth is on the menu, and
they reproduced at each plot. Releasing beetles near leading edges of the
moth's spread, for example, in Michigan, could efficiently get the predators
established to start hunting down pesky caterpillars. Study collaborators
were with ARS, Connecticut Agricultural Experiment Station, Michigan State
University, West Virginia University and USDA's Animal
and Plant Health Inspection Service. The West Virginia scientist is
conducting new tests, and releasing Calosoma to help protect irreplaceable
chinkapin oak trees--several hundred years old--at the university's arboretum.
Meanwhile, a Connecticut researcher is devising an artificial diet for rearing
large numbers of Calosoma beetles in the laboratory.
Beneficial Insects Introduction Research Laboratory, Newark, DE
Roger W. Fuester, (302) 731-7330
Interplanting two or more oilseed crops in alternating strips produced
yields similar to conventional one-crop systems. In field tests, ARS
researchers strip-cropped canola and soybeans. The strip crops reduced the
need for insecticides, helped control weeds without chemicals, used less
fertilizer and produced more and better quality oil. Another plus: Seed
oil and crude protein concentrations were higher in the strip-cropped system.
Results indicate intercropping can be as economical and profitable as conventional
systems.
Plant Science Research
Unit, St. Paul, MN
Carroll Vance, (612) 625-5715
Weevils that devour stored grain could have their meal tickets revoked
by a tiny wasp that is a natural enemy. The weevils are becoming resistant
to the pesticide malathion, the conventional weapon used against them. But
the wasps, Anisopteromalus calandrae, can survive malathion applications.
ARS scientists found that this makes the wasps a promising tool in a two-punch
strategy--malathion to kill weevils that haven't developed resistance plus
wasps to wipe out the rest. Female wasps deposit eggs on weevil larvae,
ensuring a future food source for new-born wasps. ARS researchers say the
wasps' malathion resistance is the result of a single gene that could be
transferred to other species of beneficial insects. That would give farmers
an option in using integrated pest management (IPM) strategies to combat
pests that develop resistance to malathion.
Biological Research, Manhattan,
KS
James E. Baker, (913) 776-2785
A protein that helps destructive lygus bugs sniff out cotton plants--or
prospective mates--could prove to be the pests' undoing. That's if ARS
scientists can exploit the protein as a new alternative to chemical insecticides.
One possibility: block the protein's production as the bug nears maturity.
Then, the bug may be unable to heed important chemical cues--odors from
tasty plants or the sex attractant emitted by a potential mate. Researchers
isolated the "odorant binding protein" (OBP) from tiny hairs on
the bug's antenna. This chemical-sensing organ serves as a nose and shuttles
odor molecules to special nerve cells that alert the insect that food or
other bugs are near. OBP's are found in humans and other animals. But they've
been found in only three insects: the lygus bug and two species of moth.
In the United States, the lygus bug is a costly pest of cotton, alfalfa,
soybean and other crops. Its feeding robs plants of vital nutrients, causing
them to wilt and die.
Insect Chemical Ecology
Laboratory, Beltsville, MD
Joseph C. Dickens, (301) 504-5223
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