Since genetic engineers devised herbicide-resistant crops in the mid-1990s, weed killers such as Roundup have become the wonder drugs of the farming industry, clearing out pest plants while leaving corn and soybeans intact. But weeds are developing resistance as well. Weed specialist Ian Heap and his colleagues at the International Survey for Herbicide Resistant Weeds in Corvallis, Oregon, have found that more than 50 species of herbicide-tolerant weeds have popped up just since 1995—a trend fueled by the 2 billion pounds of herbicide farmers dump on their crops every year. "We're very concerned, because so many soy and corn farmers rely solely on Roundup for weed control," he says. He is urging farmers to use different herbicides each year and to invest in old-fashioned methods of weed control, such as tilling the soil.
Graphic data courtesy of weedscience.com.