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New fact sheet series for specialty crop growers focuses on dicamba and 2,4-D drift

Dicamba-related drift is causing significant stress for agricultural regulators, and soybean farmers this year. For many specialty crop growers, though, this is familiar ground as their crops are especially sensitive to drift.

Since 2016, soybean farmers have quickly adopted dicamba- and 2,4-D-ready crops in their fight against herbicide-resistant weeds. However, the expanded use of these herbicides during the growing season has led to an increased threat of drift damage for specialty crop growers.

High-value crops such as grapes, tomatoes, and sweet potatoes can be damaged by concentrations of 1/300th the labeled rate or lower. While recent legal issues have limited the use of three dicamba products for this growing season, both dicamba and 2,4-D will continue to pose a risk in areas with diversified or organic production.

A new fact sheet series, co-written by agricultural specialists at The Ohio State University and Purdue University, is available to help specialty crop growers prepare for and respond to possible dicamba and 2,4-D drift. The series provides tips for being proactive, detailed steps for documenting and responding to damage, and a brief background on why dicamba and 2,4-D have been especially problematic.

When it comes to preparing for drift, “vigilance and communications are the two big things,” said Doug Doohan, weed specialist and professor of horticulture and crop science with Ohio State’s College of Food, Agricultural, and Environmental Sciences (CFAES). “Knowing who your neighbors are, talking to them about your plans, talking to them about their plans, being aware of who’s doing what on the land and when.”

But who is your neighbor when it comes to drift? Just how far can dicamba drift travel? Most spray droplet drift will move only short distances. This type of damage is generally limited to adjacent fields. However, dicamba and 2,4-D are likely to drift farther as gases or via temperature inversions. Temperature inversions can be especially damaging, moving suspended pesticides in a fog-like layer for longer distances.

“There’s all kinds of circumstantial evidence of much greater movement,” Doohan said. “When you’re talking inversions, if an inversion is motivated by a 2–3 mph wind, it could go miles—especially if the conditions persist through the evening.”

Doohan has helped investigate several drift cases and is one of the co-authors of the new fact sheet series. He encourages growers to establish a standard operating procedure (SOP) to prepare for a drift incident, just as they might for food safety concerns. He also stresses the importance of documenting suspected drift quickly, thoroughly, and repeatedly. The new fact sheet series offers detailed suggestions for these activities.

“If you see something, document it,” he said. “Use your cell phone. You can always delete unneeded photos later, but you can’t go back in time and get the picture you wish you had taken.”

A frequently asked questions (FAQ) fact sheet highlights various concerns pertinent to specialty crop production. The series sought input from a variety of crop and herbicide specialists across the United States, as well as from state regulatory agencies.

The fact sheets are available at go.osu.edu/ipm-drift.

The new fact sheet series was produced with support from the North Central IPM Center Working Group on Herbicide-Drift Risk Management. The working group organized in fall 2019 and plans additional work in the coming year, including more resources and an anonymous survey of specialty crop growers to better assess the extent and frequency of drift damage throughout the north central region.

The North Central IPM Center serves Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin. It is supported by the U.S. Department of Agriculture’s National Institute of Food and Agriculture.

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