Rotate crop herbicides, advises weed specialist

Texas crop farmers are advised to give serious consideration to rotating herbicides as the potential for resistance to certain compounds becomes more common, according to a Texas AgriLife Extension Service specialist.

“Weed resistance to some herbicides is affecting a large number of acres in the southeastern United States,” said Paul Baumann at the recent Stiles Farm Field Day at Thrall, Texas.

“Glyphosate-resistant Palmer amaranth pigweed and others have been documented in other parts of the country. The occurrence of these [glyphosate-resistant] weeds has been very limited,” he said.

Key Points

• Potential weed resistance to herbicide is gaining attention.

• Farmers should seriously consider rotating herbicides.

• Some herbicides with different modes of action may help.


Baumann told more than 300 producers that another pigweed species, common water hemp, also has displayed resistance to glyphosate and several ALS inhibitor herbicides along the Texas Gulf Coast region.

“My opinion, shared by many of my weed scientist peers in Texas, is that weed resistance has not been a major issue for us yet,” he said. “This is because, along with using Roundup or other glyphosate products, we also use soil-active chemistries, such as yellow herbicides in cotton” and other crops.

Different modes of action

Baumann said different weed treatments have helped manage some of the resistance issues, “by throwing different herbicide modes of action in the mix.

“No question, we will continue to see some weed resistance in Texas,” the specialist said.

Farmers can guard against weed resistance by using alternatives to glyphosate at times, or adding another herbicide to the program that has a different mode of action, controlling the targeted weeds.

Actions to take

“The point is, from a research standpoint, we have got to do two things: We have to look at alternative chemistries to see if they will perform, especially against pigweed or water hemp,” Baumann said. “We’ve got to do tests so that we can recommend to our growers methods to control these types of weeds. We also need to develop specific herbicide programs to keep from having resistance issues.

“If we continue to employ a single herbicide-use pattern, such as glyphosate products year after year on crop after crop and not putting another herbicide chemistry in the program, whether it be [for] corn or cotton, we will develop resistance issues.”

Meanwhile, another specialist noted the 2010 Texas cotton crop has made great progress during this season.

Gaylon Morgan, AgriLife Extension Service cotton specialist, said the Texas cotton crop is in “a whole lot better situation this year as opposed to 2009.”

Cotton looking good

“We had 34% abandonment in Texas last year, and only 3% this year,” Morgan noted. “We’re looking forward to a good crop. This year, the state is in good to very good condition with only about a third in fair condition, and 5% in poor condition. We’re pretty good overall.”

During the field day, two $4,000 Stiles Farm Foundation scholarships were given to area students headed to college. The students receiving scholarships were Weston Fisher of Milam County and Helen Hardy of Williamson County.

Fannin is with Texas A&M Agriculture Communications, College Station.

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time to ROTATE: Paul Baumann, Texas AgriLife Extension Service state weed specialist, discusses weed resistance to herbicide and rotation of herbicides at the recent Stiles Farm Field Day at Thrall, Texas.

Photo: Texas AgriLife Research

This article published in the September, 2010 edition of THE FARMER-STOCKMAN.

All rights reserved. Copyright Farm Progress Cos. 2010.