Since the early 2000s, U.S. farmers have dramatically increased their use of controversial insecticides suspected of playing a role in the decline of pollinating insects, such as honeybees. Called neonicotinoids, these insecticides are a class of neuroactive chemicals similar to nicotine.
The boom in neonicotinoid use came about as many agricultural companies and farmers started smothering seeds with the insecticide before planting, a preemptive treatment not monitored by the U.S. Department of Agriculture, researchers report online April 2 in Environmental Science & Technology. In the new study, entomologists Margaret Douglas and John Tooker, both of Penn State University in University Park, combined agricultural data from the USDA, the U.S. Geological Survey, state records and a maize seed supplier. Using estimates of how much of the insecticide was sold and how much was used for nonseed treatments, the authors calculated the rise of seed treatments on the country’s biggest crops, including maize and soybeans.
All crops saw boosts in seed treatments. The portion of maize cropland getting neonicotinoid-treated seeds, for example, rose from close to zero in 2003 to more than 79 percent in 2011. In that year, authors estimate that at least 42 million hectares of cropland was planted with treated seed — an area roughly the size of the state of California.