MIDDAY, MID-JUNE, MERCURY IN THE MID-90s. On the Arkansas Northeastern College campus in Blytheville, Dan Scheiman peers through binoculars at a big oak. Robins and cardinals flit nearby, but it’s not a bird that’s caught his eye. Something is wrong with the tree.
He marches over for a closer look. The leaves are curling inward, an abnormality called cupping. “Top to bottom,” he observes, circling the trunk. “All around.” Scheiman, plants for birds program manager for Audubon Delta, Audubon’s regional office, can’t be certain of the culprit without sending a sample to a lab. But he has no doubt: Cupping is a classic sign of exposure to the herbicide dicamba.
Though used for decades to combat weeds on farms and lawns, dicamba took off six years ago with the introduction of crops genetically engineered to tolerate being sprayed with the chemical while surrounding weeds die. The EPA figures roughly two-thirds of U.S. soybeans and three-quarters of cotton by acreage are dicamba-tolerant.
Trouble is, dicamba won’t stay put. Particles of any weedkiller can drift on the wind, but dicamba travels from its target without so much as a breeze. When temperatures are high enough—the exact threshold is uncertain—it evaporates, rises, and roams ghostlike across the landscape. It can become airborne days after it’s sprayed and drift for miles. While exposure to the vapor hasn’t been proven to significantly sicken humans or birds, it injures or kills broadleaf plants that people and wildlife depend on, from soybeans to strawberries to sweetgum.
MAY SAY DICAMBA’S DAMAGE TO CROPS, ECOSYSTEMS, AND RURAL COMMUNITIES IS AMONG THE WORST THINGS EVER TO BEFALL AMERICAN AGRICULTURE.
Many farmers, scientists, and advocates say dicamba’s damage to crops, ecosystems, and rural communities is among the worst things ever to befall American agriculture. Growers who rely on the weedkiller, meanwhile, say they need it to protect their yields from stubborn nemeses no longer fazed by glyphosate, another herbicide. No place has seen more conflict than the Arkansas Delta—part of the fertile plain flanking the Mississippi River—with its abundance of soybeans and cotton, broiling summers, and frequent temperature inversions that suspend dicamba vapor
