Insect Resistance Management Fact Sheet For Bt Corn

Bt corn has proven to be an important technology to help corn growers control damaging insect pests and produce higher yields and better quality grain.

Insect Resistance Management (IRM)

To preserve the many benefits of Bt corn technology, the implementation of an IRM plan is essential. Experts agree, and government regulations require, that an effective Bt corn IRM plan includes the planting of a non-Bt refuge (a block of non-Bt corn) planted close to your Bt corn acres.

All Bt corn products require implementation of an IRM program according to the refuge size, distance guidelines and insecticide usage described in this fact sheet.

Growers who fail to follow IRM requirements risk losing access to Bt corn technology.

What are the Requirements of the Corn Borer IRM?

• Plant at least 20% of your corn acres to refuge hybrids
• In cotton producing regions, refuge must be 50%
• Must be planted within 1/2 mile of the refuge hybrids
• Refuge can be planted as strips within the Bt field; the refuge strips must be at least 4 rows wide
• Refuge may be treated with conventional pesticides only if economic thresholds are reached for target insects
• Bt-based sprayable insecticides cannot be used on the refuge corn
• Appropriate refuge must be planted on every farm with Bt corn

What are the requirements of Corn Rootworm IRM?

• Plant at least 20% of your corn acres to refuge hybrids
• The corn rootworm protected Bt corn must be planted within the same field or adjacent to refuge hybrids
• The refuge can be planted as blocks within or adjacent to the Bt field or strips of at least four rows wide within the Bt corn field
• The corn refuge can be treated for control of corn rootworm larvae and other soil pests with soil, seed, or foliar applied insecticides
• The refuge can be treated with a non-Bt insecticide to control late season pests such as corn borer
• If aerial insecticides are used to treat CRW adults on the refuge, the same treatment must also be applied to the corn rootworm protected Bt corn acres
• Pests on the corn rootworm protection Bt corn can be treated at any time without treating the refuge corn
• Appropriate refuges must be planted on every farm with Bt corn

What are the Corn Rootworm and Corn Borer stacked requirements?

• Plant at least 20% of your corn acres to refuge hybrids
• In cotton producing regions, refuge must be 50% (because of corn borer)
• Must be planted within the same field or adjacent to refuge hybrids (because of rootworm)
• The refuge can be planted as blocks within or adjacent to the Bt field or strips of at least four rows wide within the Bt corn field
• Appropriate refuges must be planted on every farm with Bt corn
• Be sure to consult your dealer when making choices concerning your stacked traits

Refuge Planting Options

As illustrated below, the appropriate size non-Bt corn refuge may be planted a number of ways:

Block Refuge (Adjacent) A block of non-Bt corn adjacent to the Bt corn field	Block Refuge (Within) A block of non-Bt corn within the Bt corn field	Refuge Perimeter Non-Bt corn surrounding the Bt corn field
Split Planter Refuge Strips of non-Bt corn at least 4 rows wide with the Bt corn field (6 rows preferred)	Pivot Corners Refuge Non-Bt corn in pivot corners within the Bt corn field	Separate Field Refuge A separate field of non-Bt corn within 1/2 mile of the Bt corn field (1/4 mile preferred)
Bt corn field	Non-Bt refuge	Soybeans
VT Triple Adjacent

Insecticide Usage in Non-Bt Refuges

Your non-Bt corn refuge may be treated with conventional insecticides ONLY if target pest pressure reaches economic thresholds. Bt-based foliar insecticides are NOT to be used within the refuge.

Rufuge Management

In order to maximize the effectiveness of the refuge, you should manage your non-Bt corn and Bt corn in a similar manner. This can be accomplished by planting your non-Bt corn as close to and at the same time as your Bt corn. In addition, select non-Bt hybrids and Bt hybrids that have similar growth and development characteristics.

Seed companies, universities and the National Corn Growers Association (NCGA) all agree that there should be unified commitment to responsible stewardship of Bt technology so it can be preserved as an important tool in corn management.

The NCGA encourages producers to implement IRM plans when planting Bt corn. This EPA requirement is the right thing to do in order to preserve this important technology.