What is in this article?:
- Drought made it hard to grow cotton this year and is also making it hard to kill the cotton in preparation for wheat or other follow-up crops.
- There is no ‘one recommendation fits all’ for killing cotton stalks.
- Tillage and herbicide applications may be effective.
On the herbicide front, more than 10 years of applied research and demonstration trials have been initiated to evaluate the efficacy of chemical-stalk destruction, he said.
Previous research in Texas has indicated the most effective and consistent herbicide is 2, 4-D at 1 to 1.5 pounds of active ingredient per acre on standing, freshly shredded (one to four hours after shredding) or delayed applications (two to three weeks after shredding).
The herbicide Clarity, at 0.5 pound of active ingredient per acre, has been the best alternative to 2, 4-D, but has typically provided slightly less kill than 2, 4-D, he said.
Although 2, 4-D and Clarity typically provide more than 90 percent kill, where growing conditions remain favorable for approximately 60 days or more after herbicide application, a follow-up treatment may be required to kill any remaining host plants, Morgan said. If a second herbicide application is required, 2, 4-D at 0.5 to 1 pound of active ingredient per acre or Clarity at 0.5 pound of active ingredient per acre is recommended.
In years with early harvest and a warm fall, growers may see some advantage to the delayed herbicide applications, two to three weeks after shredding, he said.
“The herbicide efficacy is comparable, but this delayed application may decrease the chance of a second application being necessary and can also help control emerging seedling cotton,” Morgan said. “However, herbicide efficacy can be hindered as temperatures cool in the fall.”
Problems also may occur in cotton fields that are planted into wheat, he said. This cropping sequence has numerous benefits, but one challenge in South, Central and East Texas is destroying the cotton crop prior to planting wheat or after wheat establishment.
When destroying cotton stalks prior to planting wheat, remember 2, 4-D has a minimum of a 30-day planting restriction for wheat, Morgan said. Even observing this 30-day planting restriction, some wheat injury can occur, if inadequate rainfall occurs. At the recommended rate of Clarity for cotton stalk destruction, the plant-back restriction is 44 days.
When destroying cotton stalks in established wheat fields, 2, 4-D is labeled for application to fully tillered wheat through the boot stage, he said.
Applications of 2, 4-D prior to the full-tiller stage can significantly decrease yields. Clarity is labeled for application from wheat emergence through jointing; however, the labeled rate is a maximum of 4 ounces per acre.
Morgan said several other products are labeled for post-emergence broadleaf weed control in wheat, include Affinity Broadspec, Aim, Buctril, CleanWave, ET, Huskie, Peak and Starane, and this should provide sufficient suppression of cotton stalks until the first killing freeze occurs on cotton.
He referenced several publications to provide more information, including “Managing Volunteer Cotton in Grain Crops,” “Weed Control Recommendations in Wheat” and “Cotton Stalk Destruction with Herbicides.”