Weed control issues account for two of the top five concerns cotton farmers cited in a recent Cotton Incorporated survey, and herbicide resistance is number two on the list.

But even with resistance, cotton producers still have effective and affordable options to control weeds, if they follow a systems approach and do a little homework, says Shane Osborne, Oklahoma State University associate Extension specialist.

Osborne, addressing the inaugural Red River Crops Conference recently in Altus, Okla., said pigweed and horseweed take the top two spots as most difficult weed in Oklahoma cotton. But, unlike other cotton producing states, especially in the Mid-south and Southeast, horseweed takes the top spot, cited by 46 percent of respondents as the worst weed problem. Pigweed was listed by 31 percent. Moringglory came in third at 15 percent and common groundsel was fourth with 8 percent.

Picking variety is critical decision for cotton farmers.

Osborne says 82 percent of those recently surveyed said they have resistant pigweed and 78 percent said they had resistant horseweed.

“Cotton farmers currently spend about $32 per acre on herbicides, on average,” Osborne said. “That’s not bad. At current prices that amounts to about 40 pounds of cotton. We are in a lot better shape than other areas of the Cotton Belt.”

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He said identification is important. Farmers should determine if they have pigweed or horseweed. “It’s important to know so we can focus programs and know what to target. We have glyphosate resistant horseweed all over and we began to pick up resistant pigweed a few years ago.”

He said farmers have “a lot of choices to control horseweed,” including pre-plant and burn-down options. But controlling horseweed in season is not an option. “We have no effective herbicides to use in season. Focus on pre-plant; that’s when we can control horseweed.”

Timing is critical. He recommends treating horseweed at the rosette stage. “It makes a big difference in the level of control we get from the rosette stage to early bolt.”

He also cautions producers to look at the 30-day plant-back restriction after using 2,4-D and 21 days (after a 1-inch rain) on dicamba. “And do not use if rainfall for the area averages less than 25 inches per year. Observe the label.”