Mortensen suggested that federal regulation should play a strong role in forestalling the further development of herbicide-resistant weeds. He advocated steps that could significantly improve the sustainability of weed-management practices in American agriculture.

"Biotech companies are trying to deal with the problem by engineering new crop varieties that will be immune to more than one herbicide, but even those products will eventually run into resistance problems if farmers aren't careful," he said. "The U.S. Environmental Protection Agency and the U.S. Department of Agriculture's Animal and Plant Health Inspection Service should require that registration of new herbicide/transgenic crop combinations explicitly address herbicide-resistance management.

"Regulations should limit repeated use of herbicides in ways that select for resistance or that result in increased reliance on greater amounts of herbicide to achieve weed control," Mortensen added. "We should provide environmental market incentives, possibly through the farm bill, to adopt a broader integration of tactics for managing weeds.

"Transgene seed and associated herbicides should be taxed and proceeds used to fund and implement research and education aimed at advancing ecologically based integrated weed management," he concluded.