An unusually large number of complaints of crop damage by herbicides that include dicamba have been reported this year, says EPA in a compliance advisory that warns it is illegal to use the weedkiller on cotton or soybeans during the growing season. Farmers in 10 states have complained to EPA and state officials of dicamba damage, with Missouri suffering the most widespread impact from herbicide “drift” from nearby fields.
The damage is believed to occur because some farmers planted dicamba-resistant GE soybeans and used an unapproved version of the weedkiller. Seed companies and growers are turning to dicamba because weeds in some regions are developing resistance to glyphosate, the most widely used herbicide in the world.
“Missouri growers estimate that more than 42,000 acres of crops have been adversely affected,” said EPA. The 117 complaints in Missouri include peaches, tomatoes, cantaloupes, watermelons, rice, cotton, peas, peanuts, alfalfa and soybeans. “Similar complaints alleging misuse of dicamba products have been received by Alabama, Arkansas, Illinois, Kentucky, Minnesota, Mississippi, North Carolina, Tennessee and Texas,” said EPA.
In Arkansas, where 28 complaints are on record, the state plant board “will soon consider a wide range of options to curb the problem” of dicamba drift, including a $25,000 fine for egregious violations, says Delta Farm Press. If the board endorse the idea, the Legislature would have to approve it. Other ideas include banning some types of dicamba herbicides, tighter controls on when some less-volatile formulations of dicamba can be used, and a one-mile buffer from susceptible crops when the weedkiller is used on pasture and rangeland.
Cotton and soybeans are the first crops genetically engineered to tolerate doses of dicamba. The USDA approved cultivation of the crops in January 2015, but EPA has not yet approved the use of dicamba on those crops. Earlier this year, EPA proposed rules for use of dicamba to control weeds in fields where the new varieties are being grown. The agency is reviewing public comments on the proposal along with the results of the investigations into complaints of dicamba drift. EPA says it aims for a final decision this year.
“The EPA has not registered any dicamba herbicides for application at planting or over the top of growing cotton or soybean plants, including crops genetically modified to tolerate dicamba,” says the advisory. At present, dicamba is restricted to pre-plant and post-harvest “burn down” of vegetation.
In another approach to solving herbicide resistance in weeds, seed companies have developed crops that tolerate a combination of glyphosate and 2,4-D weedkillers.