What is in this article?:
- Texas growers now facing reality of resistant weeds
- Late-season scouting
• In the last two years Texas has come into the real world of weed control issues.
• Glyphosate resistant common waterhemp has been identified in southeast and central Texas.
• Glyphosate resistant Palmer amaranth (pigweed) has been identified on the Texas High Plains.
A SINGLE uncontrolled common waterhemp plant (resistant) is surrounded by controlled plant carcasses.
Baumann recommends farmers pay attention to their fields late in the season, looking for weeds that escaped all attempts at control. “It might be too late in some parts of Texas,” Baumann says, “but farmers can check for patches of weeds that were not killed with glyphosate applications.” Fields with consistent infestations across the field could indicate application errors, but those patches that were not controlled at all could result from one or two resistant weeds going to seed last year.
“I’m seeing more of this than I want to,” Baumann said.
He’s looking at program approaches to control and prevent resistance. “We’re considering the whole ball of wax,” he says. “That includes a soil-applied herbicide followed by a postemergence herbicide, with or without Roundup (glyphosate).”
Dicamba, and 2, 4-D also may play roles in resistant weed management. “We may use all the traditional methods and then incorporate new technology that could be available in the next couple of years, including dicamba and 2, 4-D tolerant cotton varieties.
“We will not throw Roundup under the bus,” he says. “It’s too good and too economical. But we have to be more aware of other modes of action.”
Roundup resistance should provide a lesson. “As we get new technology, including, dicamba and 2, 4-D tolerance, we must make certain we don’t ruin it by neglecting to use herbicides with alternate sites of action,” Baumann says.
A back to the future approach also may be necessary. “We might see some growers go back to more conventional cotton varieties, back to ground zero, the approach we used 15 years ago to control weeds before we had Roundup-resistant varieties.”
Growers had other serious issues back then, including things like silver leaf nightshade in the High Plains and morningglory in central Texas. “We have really reduced the impact of those weeds,” Baumann says. “Thanks to technology, we cleaned those problems out of the fields.”
That could give farmers a window of opportunity to go back to “the cadre of herbicides we were using 15 years ago. We may see those (old) problems develop, but we will have new products in the pipeline.
“We still have a good selection of chemicals available. We still have holes, but those will be filled, and we will keep working around these issues.”