Two growing patterns threaten current crop production practices in intensive agriculture: the cross-pollination of genetically modified (GM) crop varieties with conventional varieties, and the germination of volunteer GM seeds (seeds dropped, blown, or inadvertently planted). Crosspollination of GM crops with crop varieties destined for non-GM, GM-free, or 'organic' niche markets is of great concern to the corresponding producers. The growth of volunteer GM seeds can be controlled chemically, but at an added cost for producers. Both of these problems must be rapidly addressed to ensure that the adoption rate of GM crops remains high and that the commercialization of future varieties is not jeopardized.