The Arkansas Department of Agriculture received 986 complaints about off-target applications of dicamba on non-dicamba-tolerant soybeans in 2017. The Georgia Department of Agriculture received 0 complaints.
There’s been a lot of speculation about why farmers in the Mid-South states registered so many more dicamba incidents and why those in the Southeast so few — Alabama, Georgia, North Carolina and South Carolina and Virginia had a total of 25.
That didn’t happen by accident, according to Dr. Stanley Culpepper, professor and Extension agronomist with the University of Georgia and a speaker at the recent annual meeting of The Pesticide Stewardship Alliance in Memphis, Tenn. Culpepper’s topic was Auxin Symptomology/Sensitivity on Horticultural Crops.
“I thought we were one of the most challenging states to be implementing the new technology because we have 170,000 acres of vegetables worth more than a billion dollars,” he said. “And I was thinking there’s no way we’re going to do this successfully.
“I think because of the value of these crops our growers treated this with a little more respect. And I don’t think that would have happened had we not had this experience with these crops. I thought it might be our downfall, but it may have been one of the positives that helped us make really good decisions.”
Culpepper said Georgia has seen its share of off-target complaints in the past, primarily from herbicide drift, which he said was the “least favorite part of my job.”
Off-target incidents in 2010 and 2011 led Culpepper and fellow researchers to conduct 70 field trials to get a better idea of the impact of herbicides drifting on non-target, highly sensitive vegetable crops. The results were striking.
“Most growers will agree that glyphosate (the active ingredient in Roundup) can have a negative effect on crops like watermelon and tomatoes,” he said. “But once you get past a 1/50 rate of glyphosate, the damage becomes almost negligible.
“We’ve gone out past a 1/1500 rate of dicamba on snap beans and lima beans and still observed damage of 25 percent,” he said. “A farmer can spend $3,000 an acre putting in a field of snap beans.”
In 2014, the University of Georgia Extension Service responded to 289 complaints involving herbicide drift. That prompted Extension specialists to launch a program aimed at reducing pesticide drift and improving pesticide stewardship. The program incorporated some of the research by Culpepper on the sensitivity of vegetable crops to dicamba and 2,4-D.
“Once we implemented this program in 2015, 2016 and 2017, we have seen an exceptional response,” he said. “It may or may not be the training; it could be the discussion within our industry of wanting to do better.”
Following the initiation of the training effort, the number of drift complaints dropped to 150 in 2015, 99 in 2016 and 93 in 2017. “We treated 1.3 million acres with our auxin chemistry, but we did not have an official complaint to the Georgia Department of Agriculture. The University of Georgia addressed maybe 18 to 20 complaints regarding dicamba.”
One of the keys to the University of Georgia’s training is helping growers understand how far particle drift or volatility drift can go. Most farmers do not understand the dynamics of herbicide drift, Culpepper says.
“I asked my father how far he thought he was drifting, and he said about 50 feet,” Culpepper said, referring to a conversation he had on his family’s farm. “It turned out it was well over 300 feet, and that clicked with me that these guys do not know how far drift can go.”
The second behavioral change that was important to growers was identifying which fields should not be sprayed with an auxin herbicide. “In Georgia, there are a lot of fields that should not be treated with 2,4-D or dicamba,” he said.
Culpepper displayed a copy of a chart prepared by University of Georgia specialists based on their field trials. The chart includes a list of crops and the degree of herbicide damage that can be inflicted by off-target applications.
“We laminate these and on the front side is dicamba and the back side 2,4-D,” he said. “The whole objective with these is for you not to spray near these crops. We think this is one of the most important things we can do to help with these crops.”
At the end of his presentation Culpepper showed a slide that listed eight specialty crops and their estimated retail value per acre. Those values can run as high as $33,000 per acre for tomatoes grown in a raised mulch environment.
But it’s the perception of damage that can trump the value.
“We sell a lot of produce to Kroger and to Walmart,” he noted. “They now will visit our farms quite often. If someone from Kroger visits our farm, and we have drift on watermelons, they will not buy any watermelons from that field.
“And if you don’t take the field out while they’re standing there, they will not buy any more watermelons from that farm. They will not tolerate anything. They do not care about residue; they do not care about EPA or the University of Georgia. What they care about is their supply chain down the line and knowing there is no illegal residue involved.”