Good news for cotton growers: Two of their biggest pests, cotton bollworm
and tobacco budworm, have not become more resistant to the natural insecticide
Bacillus thuringiensis (Bt), according to
Agricultural Research Service
That finding comes from an ongoing ARS project to develop a reliable system
for tracking insect resistance to Bt. In 1996-97, the ARS researchers studied
67 insect colonies (24 tobacco budworm and 43 cotton bollworm) in nine states.
Monsanto first developed crops with built-in Bt in the early 1990s as an
alternative to synthetic insecticides. Today, Bt-formulated crops are a major
source of insect control. Many crops, including corn, cotton and potatoes, have
been genetically engineered with the Bt gene to provide "homegrown"
protection against pests. Cotton with built-in Bt is grown throughout the
United States and in Australia.
Over time, some insects can develop resistance to insecticides, which means
more chemicals must be applied to achieve control. This can lead to
environmental hazards as well as increased costs for the grower. Several
pests, including the indianmeal moth, the diamondback moth and at least nine
other insects, have developed resistance to Bt.
ARS researchers plan to establish Bt.-resistance thresholds that would
trigger remedial action. They're also working to determine the appropriate
actions to take if resistance is discovered.
Scientific contact: Dick D. Hardee,
Management Research Unit, Stoneville, Miss., phone (601) 686-5231, fax (601)