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Managing Bt Corn Hybrids

UW-Extension publication provides information on insect resistance.

May 8, 2008

2 Min Read

Planning to plant Bt corn hybrids this spring? If so,
you'll want to read the University of Wisconsin-Extension's "Insect
Resistance Management and Refuge Requirements for Bt Corn."

This booklet provides information for growers and consultants about
how to comply with the requirement of having an insect resistance
management (IRM) plan in place when growing Bt corn hybrids.

"The IRM plan is implemented by planting refuge corn acres on each
farm where a Bt corn hybrid is planted," said Eileen Cullen,
UW-Madison/Extension field and forage crop specialist. "Refuge corn
acres are hybrids that do not contain the Bt insect trait used in the
Bt planting. The refuge must be planted to 20 percent of the corn
acreage on each farm, and there are specific configuration and
distance requirements."

As a condition of registration of Bt corn, the U.S. Environmental
Protection Agency requires all farmers who use Bt corn hybrids to
plant 20 percent of their corn acreage to a refuge. The aim of this
strategy is to provide an ample supply of insects that remain
susceptible to the Bt toxin. The non-Bt refuge will decrease the odds
that a resistant insect can emerge from a Bt field and choose another
resistant insect as a mate. By preventing the pairing of resistant
genes, these refuges help ensure that susceptibility is passed on to

To implement EPA's IRM refuge requirement, the Bt corn registrants
(e.g., Monsanto, Dow AgroSciences, Syngenta, and Pioneer Hi-Bred)
enter into a contractual agreement with every farmer who buys Bt corn
that obligates the farmer to plant the appropriate refuge. EPA also
requires the Bt corn registrants to establish a compliance assurance
monitoring program (CAP) to identify and address noncompliant
farmers. If a farm is found to be out of compliance, a grower will
receive a warning from the seed company. If the farm is out of
compliance for a second year, the seed company will refuse to sell Bt
corn to the grower. Field inspections may be performed by seed
companies through the compliance assurance monitoring program. The
purpose of the IRM refuge requirement is to maintain efficacy of Bt
crops as an insect pest management tool by preventing or delaying
development of insect resistance to these traits.

Booklets are available through UW-Extension Publications on the Web
at http://learningstore.uwex.edu/

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