Refuge Requirements for Bt Corn

February 12, 2003   10(2):15-16

Joe Lauer, Corn Agronomist

Bt corn continues to perform as well and possibly even better than normal elite commercial hybrids available in Wisconsin (see the last issue of the Wisconsin Crop Manager). It is a technology that improves yield and quality and helps farmers control damaging insect pests including European corn borer. The following article is derived from the website:

To preserve the benefits of Bt corn technology the planting of a non-Bt refuge is recommended. All Bt corn products designed to control European corn borer, southwestern corn borer and corn earworm are required to have a non-Bt refuge. Growers who fail to follow these requirements risk losing access to Bt corn technology. In order to maximize the effectiveness of the refuge, you should manage your non-Bt corn and Bt corn in a similar manner by 1) planting your non-Bt corn as close to and at the same time as your Bt corn, and 2) selecting non-Bt hybrids and Bt hybrids that have similar growth and development characteristics.

Refuge Size Requirements

Your corn growing area must have at least at least 20% refuge. A non-Bt refuge must be planted within 1/2 mile of each Bt corn field, but preferably within 1/4 mile.

Refuge Planting Options The appropriate size non-Bt corn refuge may be planted a number of ways:
= Bt corn field, = Non-Bt refuge, = Soybeans
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 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)

Insecticide Usage in Non-Bt Refuges

In non-Bt corn refuges conventional insecticides can be applied ONLY if target pest pressure reaches economic thresholds. Bt-based foliar insecticides are NOT to be used within the refuge.

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