Charcoal may guard specialty crops against herbicide drift

By Aaron Viner

Dicamba drift has made headlines around its impact on corn and soybean crops in the Midwest, but it is impacting another key agriculture market — fruits and vegetables.

Justin Keay, University of Missouri horticultural field specialist, wrote in a summer report that a survey of Missouri specialty crop growers in 2019 indicated herbicide drift was a ″serious barrier″ to farming fruits and vegetables. Part of the issue came from direct impacts on the crop, but the others came from consumer relations.

″Some growers mentioned losing markets for their specialty crops because they couldn’t guarantee their clients that their produce was free of herbicide drift,″ Keay said.

Some researchers are now looking to find a solution to that problem. This past summer, researchers at the University of Missouri worked with activated charcoal in an effort to filter out dicamba that could move into unwanted areas — similar to how many water filtration systems use the substance to take out unwanted chemicals.

The researchers used a fence treated with charcoal next to a field utilizing a dicamba-treated crop to see if it could reduce some of the damage.

Missouri horticulturalist Reid Smeda is a part of the research, and said in an interview this fall that many fields are already established for corn or soybeans, with greenhouses in place for fruits and vegetables. Moving either is difficult or unreasonable, meaning a way to make it easier foreveryone is crucial.

″They can’t move their crops, so they have to do something,″ Smeda said. ″And unless the technology goes away, we have to adapt. Activated charcoal fencing is one attempt to do that.″

He said this isn’t likely to be something seen on a large-scale farm, but in certain fields or even in Missouri’s grape-growing regions, it could have a significant effect.

″I would not expect to have normally sensitive tomatoes this close to a dicamba-tolerant field,″ Smeda said of their tests. ″If you have a grape field which is close to one side of dicamba-tolerant crops, it could potentially be used.″

The use of activated charcoal isn’t a new idea, as multiple university sources cite it as a good management technique in specialty crops, including Utah State. Researchers there discuss using it in hemp production shortly after or alongside herbicide applications.

Figuring out ways to protect sensitive crops from drift is always a challenge, but it often starts with communication, Keay said.

″Inform neighbors of the presence of sensitive high-value crops and that crop damage or total loss can occur from drift events,″ he said. ″Affected growers may work with neighbors to resolve the situation through financial compensation related to the loss of investment and income from affected crops. Working with neighbors can lead to a resolution both parties are satisfied with.″

Keay also suggested using windbreaks at field borders to reduce wind speeds and therefore reduce drift, though the overall effectiveness of that has not been researched.

The most sensitive crops have proven to be tomatoes and legumes such as green beans and peas. The earliest signs of drift may be abrupt, he said.

″Growers might notice that leaves of plants begin cupping upward and appear distorted in shape,″ Keay said. ″Plants may die, and surviving plants are likely to have decreased yields.″