The most simple approach is to not plant Bt corn every year. Use Bt hybrids only in fields where the risk from corn borer infestation warrants the price premium for the seed. In addition to this approach is the preservation of refuges of non-Bt corn for the corn borer to feed on. While it may seem illogical to try to preserve the population, remember that the European corn borer has many hosts and the pest cannot be eradicated. Therefore, the next best option is to ensure that the corn borer remains susceptible to Bt.
Refuges are areas where susceptible corn cultivars are planted.
It is critical that all growers retain refuges for corn borer. Planting refuges can be done in several ways. Refuges may be planted in blocks. These blocks may be placed along field margins, along ditches or in blocks within the field. Consider the following numbers from U.S. studies.