bioGraphic: “Scientists and conservationists in the U.S. Midwest are working to stop industrial herbicides from drifting onto the region’s remaining hardwood trees. The symptoms were strange. They were the same across multiple oak species—white, swamp white, black, red, post, shingle, chinkapin, blackjack, and pin. Leaves thickened, elongated, and contorted into grotesque shapes—cupping, puckering, curling, and twisting until it was hard to tell one species from another. Veins bleached yellow, losing chlorophyll. Soon after, some of the trees died. Seth Swoboda first noticed the sickness in the spring of 2017 on his 16-hectare (40-acre) property in Nashville, Illinois, smack in the middle of some of the United States’ most productive farmland. He knocked on the door of his neighbor, Martin Kemper, and asked if there was some new oak disease going around. Kemper didn’t think so, but he had a theory. A retired biologist from the Illinois Department of Natural Resources, Kemper had noticed other oaks and native trees in the area showing similar signs of injury. He suspected a culprit that’s risky to blame in a state economically and politically steeped in agriculture: herbicide drift, or the movement of weed-killing chemicals onto nontarget plants. Swoboda’s property, a cattle pasture on oak-hickory woodland, is surrounded on four sides by industrial-scale corn and soybean operations. On a hot summer evening after a neighbor has sprayed his fields, you can smell the herbicide in the air. Heat, a stiff breeze, or a temperature inversion can hoist the molecules into the atmosphere and carry them far away. In one study, researchers found that an herbicide had been carried in the clouds for hundreds of kilometers before falling as rain.

Herbicide drift is internationally recognized as a problem for native species and closely tracked across Europe. Yet no government agency in Illinois or the surrounding states was measuring its impacts, even on the few patches of native forest left, says Kim Erndt-Pitcher, an ecotoxicologist and director of ecological health for the Illinois-based nonprofit Prairie Rivers Network. “We met with agencies and it was just really hard to convince folks that this is an issue,” Erndt-Pitcher adds. “No one was looking at the frequency of symptoms or the severity of symptoms or the distribution across the state.” So Prairie Rivers Network started a monitoring program with a shoestring budget and a handful of volunteers. One of them was Martin Kemper…”