Dicamba threat prompts new approach to herbicide

Wednesday, January 17, 2018

Expert explains issues, why new caution is justified

Dicamba, the herbicide at the center of a storm of criticism during the past year, is a valuable resource but one that could be lost to regulation if misused, reported Ben Fizette at the Barry County Soils and crops Conference, held in Cassville on Jan. 9.

A row crop producer in Lawrence and Jasper counties, Fizette is a certified crop advisor and area sales manager for MFA. He said dicamba has been around "for decades" as a growth regulator, promoting twisting and extra growth that causes broadleaf plants "to grow themselves to death."

In limited use, applied in the cool season, dicamba has not been a problem. In the past year, the arrival of Xtend Cotton and Xtend Soybeans, seed lines designed to be dicamba resistant, mid-summer applications of dicamba chemistries increased significantly. This approach, especially in the Mississippi Delta, had catastrophic consequences in the process of discarding traditional caution.

"As temperatures drop and humidity increases, controls on herbicides decrease," Fizette said.

Two main problems occurred. Applying herbicides in conditions with no wind may seem like a good idea, but Fizette said the chemicals may end of hanging suspended in the air, like smoke from a burn pile visible at dusk, Temperature inversion toward the end of the day may result in warming air above fields holding spray airborne instead of dropping it. These contribute to drift and volatilization, turning the herbicide into vapor that never touches the targeted crop.

Like fog in a bottom area, airborne herbicide can settle into unplanned places, causing serious consequences. Fizette said 311 complaints were reported in Missouri, especially around the Bootheel, and nearly 1,000 in Arkansas, where one farmer is facing murder charges for retaliation against a neighbor. As much as 3.6 million acres were affected, including a peach orchard that lost 1,200 trees.

Fizette said new chemistry has reduced volatility, but he doubted that it was possible to eliminate the potential.

"The old chemistry could move as much as four miles," he said.

Consequently, state legislatures passed new restrictions. Dicamba may only be applied in Missouri from 7:30 a.m. to 5:30 p.m. All applicators must take classes. Plants are particularly vulnerable during the flowering stage. In the Bootheel, dicamba cannot be used after June 1. Southwest Missouri producers can use it up to July 15. Some buffer requirements have been imposed.

MFA locations no longer custom apply dicamba products or sell over the counter aid formations of dicamba. Blended products are still available.

"Be a good neighbor," Fizette said. "You always should have been. Now there's oversight by the EPA and the Missouri Department of Agriculture. Fines are now up to $10,000 per violation.

"I don't want you to be scared of it," Fizette said. "I want you to respect it, just like electric fences. We don't want to lose the technology. We need these herbicides for effective weed control. If there are enough repeat offenders, products will be pulled from the market. This includes range and pasture products."

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