By Alayna DeMartini
Dicamba, a weed killer notorious in some states for spreading well beyond where it's sprayed, harming other plants along the way, is affecting growers in Ohio.
The state has received only 19 official complaints of dicamba damage to fields this year. However, there are likely three to four times as many instances of harm because people are reluctant to report their neighbors, said Mark Loux, an Ohio State University Extension weed specialist. OSU Extension is the outreach arm of the College of Food, Agricultural, and Environmental Sciences (CFAES) at The Ohio State University.
Most often, farmers don’t fault their neighbor who applied the dicamba – they fault the dicamba itself because of how extensively it can spread beyond a targeted field, even when applied correctly, Loux said.
“The sense I get from people here is, ‘This is not acceptable.’ What’s not acceptable is this movement with no ability to control it.”
Missouri and Arkansas have banned the use and sale of dicamba. In Tennessee, restrictions have been imposed on how and when dicamba is applied. And in many states, complaints about dicamba damage are mounting.
Dicamba has been used in cornfields to kill weeds for a long time. But this year, complaints about the chemical are higher because it is also being used for weed control in soybean fields – and is spreading beyond the intended target area. Just last year, Monsanto and other companies released a variety of soybeans called Xtend soybeans that can tolerate dicamba, so more soybean farmers are controlling weeds in their fields with the herbicide, which is also produced by St. Louis-based Monsanto and by German chemical company BASF.
It’s too early to tell how extensive the damage from dicamba is in Ohio, said Matthew Beal, chief division of plant health for the Ohio Department of Agriculture, the agency that investigates reports of dicamba damage and gives its findings to the U.S. Environmental Protection Agency.
“We want to know if there’s crop damage or a pesticide issue that could affect plants or wildlife or if pesticides are getting in the water,” Beal said. “We want people to call us.”
After dicamba is applied, it can turn into a vapor and move from the soil or surface of leaves, spreading with the wind to neighboring fields, sometimes as far as a half mile away, Loux said.
“I’ve seen it cover whole soybean fields,” he said.
While it is being sprayed onto plants, dicamba can also move with the wind as wet particles or when rain runs off a field treated with dicamba and continues onto another field or into a ditch, carrying the chemical even farther, Loux said.
The problem is that while dicamba might minimize the weeds in a field of soybeans that tolerates dicamba, it can stunt the growth of or even kill plants of various kinds if it spreads to them. And the more dicamba is used, the more growers may feel compelled to buy Xtend soybeans to protect themselves against dicamba movement from neighboring fields.
Often a plant that cannot tolerate dicamba can outgrow the damage from the chemical. However, sometimes the plant may not survive if it is exposed to too much dicamba or is already vulnerable because of weather conditions, Loux said.
Although the label on dicamba specifies when and how it should be applied, even if a grower follows all the directions, dicamba can still leave the surface of soil or leaves and go airborne, Loux said.
The safest time to apply dicamba is early in the season before crop plants have emerged, Loux said. Any dicamba that moves off target at that time and spreads to a field without growing plants is much less likely to cause harm.