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Nearly all weeds are biologically incapable of accepting pollen from currently registered Bt crops, so there is no significant risk of Bt plants cross pollinating with nearby weeds and making the weeds resistant to certain insects. The risk of cross-pollination is no greater than that of conventional crops.
The Environmental Protection Agency (EPA) assessed each of the Bt plant pesticide registrations to determine the likelihood of gene movement to weedy relatives and reported:
"& in almost all cases, the likelihood of occurrence of such movement is almost non-existent because compatible weedy relatives of Bt crops either do not occur in the United States or are isolated from areas of commercial production. Where compatible weedy relatives do exist in isolated geographic pockets, EPA has imposed stringent sale and distribution restrictions to prevent even the possibility of transgene movement to weedy relatives."
Cross Pollination and Herbicide Tolerant Crops Concerns have been expressed that cross-pollination of biotechnology crops with compatible relatives, known as outcrossing, could result in weeds that could become unmanageable. For a transfer to occur, the crop plant would have to be related to, and be sexually compatible with, the weed.
Great care is taken to develop new plant varieties that have no weedy relatives, do not outcross to weed relatives, or whose weed relatives exist only in regions where the domestic crops are not grown. If there is a potential for a gene transfer to a weed species to occur, the developer and U.S. Department of Agriculture (USDA) assess the impact during the regulatory review process.
The USDA evaluates the potential for outcrossing to weed relatives of all new plants developed through biotechnology before those plants can be approved for commercial use. There is a broad base of knowledge from which to assess these impacts because essentially all of the crops derived from biotechnology contain traits that plant breeders have worked with for years. Herbicide tolerance, for example, is well known in traditional agriculture and this experience gives those working with biotech crops critical insight to evaluate any impact of this enhanced trait and to assure safety.
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