Weed control increasingly complex

Herbicide tolerant crops designed for specific herbicides allow little room for mistakes

RIDGETOWN, Ont. — Herbicide tolerant corn and soybean options provide farmers with a weed control advantage, but caution is warranted.

A July 8 Crop Diagnostic Day in Ridgetown, was told that crops can also be set back or killed and problem weeds left unaffected if the inappropriate chemistry is applied.

The problem may grow as additional herbicide tolerant traits are introduced, according to Mike Cowbrough, a weed management specialist with Ontario’s agriculture ministry.

“We have new technologies coming onto the marketplace,” he said.

“They’re all a little different. In a few years, there could be five or six types of herbicide resistance.”

Cowbrough led farmers through several plots, each representing a crop injury situation.

One example involved the application of the herbicide Distinct on dicamba-tolerant soybeans, a trait that’s expected to be available next year. Distinct contains dicamba, the active ingredient in Banvel but also contains a product that enhances the activity of this active ingredient.

The result was significant injury.

“Just because it’s dicamba and you have dicamba-tolerant soybeans doesn’t mean you’re safe.”

Cowbrough also talked about drift concerns with certain products and the need to follow label directions carefully.

Herbicide tolerant crops are de-signed with a specific herbicide in mind. Applying a different herbicide from within the same family is asking for trouble.

Peter Sikkema, weed specialist with the University of Guelph, talked about herbicide issues in corn.

He was judicious with his response when asked if farmers are likely to make more mistakes, given the increasing complexity of chemistries and herbicide tolerant crops,.

“The potential was always there for mistakes,” he said. “The challenge is to document where you have your crops and the different traits they have. Ninety-nine percent of the time, farmers do get it right.”

Sikkema talked about several scenarios, including using a herbicide to control volunteer corn when it contains tolerance to the herbicide. Several other examples related to the failure of cleaning tanks between spray jobs.

Cowbrough and Sikkema said following label directions exactly is of paramount importance.

They also advised farmers to spray under the right weather conditions in terms of humidity and wind speed, to be especially careful when spraying near a sensitive crop and not to make any assumptions when choosing a herbicide.

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