Cotton crop consultants say farmers across the Belt can’t afford to underestimate the devastation they face from herbicide-resistant weeds.

“We have to take it seriously,” said Paul Pilsner, who works the upper Texas coast area for Coastal Crop Consulting. “We began to see waterhemp escapes about six years ago,” Pilsner said Tuesday during the Cotton Consultant’s Conference, part of early activities at the 2011 Beltwide Cotton Conferences in Atlanta.

“High rates of glyphosate would not control waterhemp,” he said. Pilsner recommended that cotton farmers use residual herbicides to augment over-the-top applications. “We need to use a full residual package. Resistant weeds will spread from two or three fields to two to three counties. And we need to be concerned about resistant weed seed production.”

Pilsner said growers also should watch for resistant johnsongrass.

Brant Baugh, Texas AgriLife Extension integrated pest management specialist in Lubbock, Texas, says Palmer amaranth is the area’s top weed problem, followed by marestail. He said resistance has not been identified in either of those weeds yet.

“Our farmers are still using pre-emergence herbicides and some are still deep-breaking land every four to five years. Also, some growers north of Lubbock practice crop rotation.”

Baugh said climate also may help delay resistance. “We have a shorter growing season in the High Plains so we have fewer generations of Palmer amaranth.”

David Hydricks, Hydricks Crop Consulting in Jonesboro, Ark., said farmers are pulling out hooded sprayers to treat herbicide resistant pigweeds. “And we are chopping weed escapes,” he said.

LibertyLink cotton adds another tool to weed resistant management, he said.

Palmer amaranth is the number one resistant weed problem for North Carolina cotton, said Billy McLawhorn, McLawhorn Crop Service. Marestail is number two.

“We can’t overstate how bad resistance can be,” McLawhorn said. “And it continues to spread. ALS herbicide resistance is coming in as well. Most farmers are using pre-emergence herbicides and we are getting more aggressive.”