Bt Crop Refuge Area
Fields with Bt crops are required to provide refuge areas to help control resistance. The refuge area supply a source of wildtype (non-mutant) insects to mate with possible resistant insects to produce nonresistant insects.
Bt crops are planted with alternating rows of regular non-Bt crops. The insects that have developed resistance to Bt have more chances of mating with an insect that has not developed resistance to Bt. By the laws of genetics, the progenies produced will be insects that are not resistant to Bt.
In the US, the EPA requires Bt corn farmers implement refuge areas to these guidelines.
1. Growers may plant up to 80% of their corn acres with Bt corn. At least 20% must be planted with non-Bt corn (refuge area)
2. Refuge area mush be within, adjacent to or near the Bt cornfields. it must be placed within 1/2 mile of the Bt field.
3. If refuge are strips within a file, the strips should be at least 4 rows.