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Refuge Requirements for Corn

Refuge Requirements for Corn

A naturally found soil bacterium, Bacillus thuringiensis (Bt), has been used as a safe, economical pesticide to control caterpillar pest for many years. When ingested by caterpillars, it has been proven to be highly effective. Furthermore, since it has no toxicity to humans and many other beneficial insects, it is readily available as a pesticide for commercial use, homeowners and organic production. Modern agricultural advancements have bred plants with this bacterium within the plant. The advantage of planting corn with this Bt technology trait is that it prevents yield loss resulting from caterpillar feeding. As such, field application of pesticides to control caterpillar pests are eliminated. Thus yield increases and cost is reduced resulting in greater agricultural sustainability and profitability.

Today, due to rapid integration of technology and early adoption of these technologies by farmers, modern agriculture has taken a progressive preventative approach to reduce the potential of pest resistance to this product. Producers that plant corn with Bt technology are required to plant a small percentage of their acres as a refuge area. A refuge area is a designated block or strip of the same crop that does not contain the Bt technology. Scientific studies show that planting the refuge will provide a breeding area for caterpillar pest. This breeding area will supply enough genetically susceptible adult moths to mate with any potentially resistant adult moths to reduce or eliminate the chance of genetic transfer of pesticide resistant genes from one generation to the next. (Resistance of pest to a pesticide results when naturally occurring genetic variations within a species is allowed to be continually transferred to subsequent generation due to the continued use of a pesticide product with a single mode of action. The greater the reproductive capacity of the pest, the faster this pesticide resistance becomes evident and spreads).

The EPA regulates resistance management policies to be used by farmers when using Bt technology seed. The exact number of acres required for refuge areas varies depending upon the Bt technology used, dominant crop grown within a region and climatic factors. Regardless of the minimum acreage requirement, to be effective the refuge area must be planted on or very near the same planting dates and have approximately the same flowering period as the corn with the Bt trait. As such, planning is necessary by the farmer to ensure that dramatic yield reductions are not realized within the refuge area and that the refuge area is highly effective.

 Potential Strategies

 20% and 50% Structured Refuge – At least 20% of the corn grown on all farms must be non-Bt when a corn plant expresses at least two Bt proteins targeted for caterpillar pests. In corn hybrids expressing a single Bt protein targeted for caterpillar pest the structured refuge is increased to 50%. This can be planted within, adjacent to or as a separate block within ½ mile of the Bt field.

Refuge in the Bag (RIB, AcreMax1 and AcreMax RW only) – With Refuge in the Bag (RIB), a small amount of non-Bt seed is pre-blended with the Bt seed making it possible to not have a separate, designated refuge area. Within the area of the US where corn is the dominant crop grown, additional precautions are not required with AcreMax RW. However, a 20% structured refuge for corn borers is still needed in cotton producing areas. Thus, Refuge in the Bag is only available in limited supply in cotton producing areas and is not a good fit, since an additional adjacent refuge is still required.