Contact: Blaine P. Friedlander Jr.
Office: 607-255-3290
E-mail: bpf2@cornell.edu
Ithaca, new York
November 14, 2000
In a war against the European corn borer, a major
pest of sweet corn, Cornell University scientists have found that an army of
tiny wasps, released just once and early in the season, can reduce damage
to ears of corn by half.
For sweet corn producers in New York and several other Northeastern
and Midwestern states this is "potentially big news," says Michael
Hoffmann, Cornell associate professor of entomology and director of the
university's New York State Integrated Pest Management program. In field tests in
which wasps were released, Hoffmann says, 6 percent of ears on average were
damaged, compared with 12 percent in fields in which wasps were not
released.
Details of the test are described in "Biological Control of European
Corn Borer with Inoculative Releases of Trichogramma ostriniae," authored
by Hoffmann; Mark Wright, Cornell research associate in entomology;
Thomas Kuhar, Cornell postdoctoral researcher in entomology; and Sylvie
Chenus, entomology technician. The article will be submitted to the Journal
of Biological Control.
The European corn borer attacks field and sweet corn, costing American
farmers about $1 billion annually in damage and control expenses.
The pest first arrived in the United States in the 1920s.
Cornell scientists have found that by releasing an army of tiny,
beneficial T. ostriniae wasps early enough in the sweet corn growing season, the
borers can be greatly suppressed without additional wasp releases or
insecticide applications. However, the grower can spray insecticide
again if necessary, and a portion of the wasps will survive and continue to
help control the borers.
Typically, these wasps are released throughout the summer growing
season in large numbers. But the new research shows that this is unnecessary.
The scientists found that only one early release was needed -- when the
sweet corn is knee-high. And growers do not need many wasps -- about
30,000 per acre. The total cost, including packaging and placement in the
field, is
less than a single application of insecticide. The Cornell scientists
conducted their field research in Tompkins, Tioga, Cayuga and Broome
counties in New York.
As late-stage larvae, borers overwinter in corn stalks. By late
spring, the larvae pupate and become adults -- corn borer moths -- and begin
laying eggs. Within a few days the eggs become larvae and begin attacking
the corn. The corn borer can tunnel through the stalk and destroy the
plant's vascular system. When the wasps are introduced to the cornfield, the
tiny females insert their eggs into corn borer eggs, effectively killing
off the borer embryo. In time, two or more wasps emerge from each borer egg.
As another cycle of wasps emerges, the female wasps seek out yet more
borer eggs and repeat the process.
"The developing borer is killed and does not have a chance to damage
the corn," says Hoffmann. "The wasp is strictly an egg parasitoid and it
searches for more corn borer eggs. We found 50 percent less damage
to sweet corn fields where the wasps were released compared to the
control fields."
In upstate New York, the beneficial wasps do not overwinter and growers
have to inoculate their fields every season. "We were hoping they
would overwinter and become permanent residents in corn fields," says
Hoffmann. "We wanted them to become a permanent member of a complex of natural
enemies that suppress the corn borer. Maybe further south they will
overwinter and become established."
Research into this problem has been conducted since 1992. Prior to
1998, funding came from the New York State Integrated Pest Management
program. Since 1998 the Pest Management Alternative program of the U.S.
Department of Agriculture (Cooperative State Research, Education and Extension
Service) has provided a three-year, $155,000 grant.
The web version of this release may be found at
http://www.news.cornell.edu/releases/Nov00/CornWasps.bpf.html
Cornell University News Service
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Cornell University
Ithaca, NY 14853
607-255-4206
cunews@cornell.edu
http://www.news.cornell.edu
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