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Despite Tighter Rules, Dicamba Damages 1.1 Million Acres of Soybeans

University weed scientists estimate at least 1.2% of U.S. soybean plantings have been damaged accidentally by the weedkiller dicamba despite stricter limits on its use this year, said a University of Missouri report. Damage was highest in Illinois, the No. 1 soybean-growing state, where 500,000 acres of the U.S. total of 1.1 million damaged acres are located. Arkansas was second with 300,000 damaged acres.

By comparison, an estimated 2.5 million acres of soy damage were reported at this point in 2017. By the end of the season, growers had filed complaints alleging dicamba damage on 3.6 million acres of soybeans. Many crops, including fruits and vegetables, are sensitive to dicamba. Landowners ranging from vegetable farmers, gardeners, and resort operators, told DTN/Progressive Farmer of damage to their property from the herbicide with no compensation or anyone taking responsibility for it.

Growers have embraced dicamba as a new tool against invasive weeds that developed a tolerance for glyphosate, the most widely used herbicide. The weedkiller is used in combination with soybeans and cotton that are genetically modified to withstand spraying with dicamba. Monsanto expected plantings of dicamba-resistant soybeans to double this year. The seed and ag chemical company said operator error was to blame in most cases of suspected dicamba damage in neighboring fields.

Weed scientist Kevin Bradley, who polled other weed scientists to compile the University of Missouri report, said volatility of the herbicide ought to be considered among the causes of crop damage. According to some analysts, dicamba may evaporate from where it is sprayed and move cloud-like to other fields. The EPA required pesticide makers to develop low-volatility versions of dicamba to use in conjunction with the GMO seeds.

“As I’ve said from the beginning on this whole issue, there are great differences in perspective about the extent of this problem and what constitutes success with this technology,” wrote Bradley. “Unfortunately, one’s perspective on this issue within agriculture seems to be closely linked to the company you work for or the type of seed you buy; a fact which disappoints me greatly and, in my opinion, is incredibly short-sighted.”

Monsanto has defended dicamba’s record and says the vast majority of growers are pleased with its results. BASF and DowDuPont also sell dicamba.

Agronomy professor Bob Hartzler at Iowa State University said state officials received 121 complaints of herbicide drift, compared with 82 complaints by early July 2017. “The significant increase in pesticide misuse cases during the first part of the growing season indicates a pesticide stewardship problem,” he wrote. Of this year’s investigations, 59 involved a growth-regulator herbicide; dicamba and 2,4-D were the most common types.

Arkansas was the epicenter of dicamba complaints last year. It banned the spraying of dicamba on row crops during the growing season this year. Other states, such as Missouri and North Dakota, instituted cut-off dates for use of dicamba or specified when the weedkiller could be used this year. The EPA revised its dicamba rules to require special training for applicators in 2017, limit the time of day when dicamba can be used, and bar spraying when winds exceed 10 mph, a reduction from the 15-mph limit of 2017.

The EPA gave two-year registration to dicamba in 2016, so the agency must revisit soon its decision on allowing use of dicamba.

Growers planted 89.6 million acres of soybeans this year, down slightly from 90.1 million acres in 2017.

Produced with FERN, non-profit reporting on food, agriculture, and environmental health.
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