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[SANET-MG] corn pest expansion due to GM crops
Corn pest expansion consequence of transgenic crops?
Wednesday, January 17, 2007
A corn pest that can devastate yields may be increasing in prevalence
across Illinois and other states because Bt crops are reducing predators
that once kept the pest at bay.
That was the word from an Iowa State University researcher who spoke
during the recent Illinois Crop Protection Technology Conference, Urbana.
Western bean cutworms, a major pest in Nebraska and Colorado, was first
detected in Illinois in 2004 and has spread to 49 counties, according to
Marlin Rice, an Extension entomologist at Iowa State.
Rice and his colleagues attempted to learn why a pest that was rare in
Iowa six years ago has spread as far east as central Ohio.
In laboratory experiments and field studies, Rice tested the bean
cutworm’s survival when placed together with corn earworm, which is the
more aggressive of the two pests and will kill the bean cutworm. Both
pests were allowed to feed on silks from Herculex and YieldGard plants.
The bean cutworms had better survival rates when they fed on YieldGard,
which is not labeled for cutworm control, compared to Herculex, which
is. Both hybrids are labeled for corn earworm control.
“Our theory is that increased (use) of Bt cotton and YieldGard corn has
suppressed (populations) of corn earworms, which are predators of
western bean cutworms. This allows (more) bean cutworms to survive,”
“YieldGard corn may be one of the reasons for more damage from western
bean cutworm,” Rice said. “It may be influencing (pest) competition in
Bean cutworms have become established in Illinois, “but we’ll have to
wait a couple of years to see if it is an economic problem,” Rice said.
He recommended farmers scout their fields and time insecticide
treatments for when eggs or young larvae reach economic thresholds.
If western bean cutworm becomes an economically damaging pest, farmers
should consider planting Herculex hybrids, he said. — Kay Shipman
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