Early last spring, American Agriculturist took flack for publishing “Take this spraying quiz for controlling resistant weeds.” It was BASF’s 10-question online Grow Smart University refresher quiz on mandatory and best management practices for knocking out resistant weeds with over-the-top use of dicamba-based postemergents XtendiMax, Engenia or FeXapan.

That article stressed the importance of following stringent spraying guidelines for the new dicamba products. Turns out, the concern was warranted, and still is — due to many drift damage complaints that arose in the South and Midwest last summer.

“The dicamba saga hasn’t been that big an issue here in Pennsylvania and the mid-Atlantic region,” says Dwight Lingenfelter, Extension weed control specialist at Penn State University. “Although about 30% of our soybeans were Xtend and many of those acres were sprayed with a dicamba product, there were no official complaints to Pennsylvania Department of Agriculture.

“Most guys who used it were rather ‘scared’ by all the problems in the South and followed all the rules — thus had minimal problems,” he says. “Acres sprayed were mostly done privately. Many dealers/custom applicators didn’t want to take on those potential liabilities.”

Tougher rules for 2018

BASF, DuPont and Monsanto are making significant label changes for over-the-top dicamba product use. Key changes include:

• Products will be reclassified for “restricted use.” Only certified applicators with dicamba-specific training can apply them. That may limit use.

• You’ll be required to maintain specific product use records.

• Maximum wind speeds must be below 10 mph (down from 15 mph) to reduce potential drift.

• Applications may be made only between dawn and dusk.

• Tank clean-out rules must be followed to avoid cross-contamination.

• Nearby sensitive crop registries must be notified.

Southern perspective
Ford Baldwin, former University of Arkansas weed scientist turned consultant, smacks the issue head-on: “People have the right to plant anything they wish without having chemicals trespassing on it.” He noted in our sister publication Delta Farm Press: “While I wish it could be different, spraying large acreages with dicamba in the summer, without off-target effects, is virtually impossible.” He sees a need for growers, suppliers and regulators to work together to develop better rules to prevent drift.

Baldwin was talking about huge fields in the South. In the Northeast and mid-Atlantic, the risks in much smaller fields should make one break out in a sweat just thinking about it. One reason: Summer temperature inversions are a critical drift factor.