The high price of diesel may encourage some cotton farmers to weigh their options this fall when removing stalks and residue from fields.

Dr. Travis Miller, Texas Cooperative Extension agronomist, said traditional tillage methods may not be the most economical approach, nor the best practice for controlling boll weevils.

"Some farmers are realizing more profit in reduced tillage methods, particularly with diesel prices hitting over the two-dollar mark (per gallon)," he said. "We want to encourage those systems that reduce tillage, and at the same time, get excellent control of cotton residue with herbicides."

Since boll weevils use squares, blooms and bolls of growing cotton as a food source, research activities using herbicides were conducted in cotton-growing regions receiving late winter freezes. Research efforts focused on the Rio Grande Valley, Upper Gulf Coast and Central Texas regions.

"We found a procedure where herbicides applied immediately after shredding cotton stalks could kill almost 100 percent with one application," Miller said. "For about the cost of one tillage operation, we can kill almost all of the cotton stalks, saving as many as three tillage operations, which used to be pretty much the norm to plow out cotton stalks and prevent regrowth."

Treatment costs were $3 per acre to $4 per acre, Miller said. Studies in Central Texas and the Upper Gulf Coast showed 2,4-D amine provided excellent control of shredded and standing cotton stalks, Miller said.

Results from research and producer experience indicated 2,4-D applied immediately following stalk shredding, or applied to standing stalks, provided the most cost-effective means of chemically destroying stalks.

"In some instances, a second application will be necessary to control emerged seedlings and any remaining live stalks," Miller said.

To achieve optimum effectiveness, some growers mounted spray booms directly on flail shredders and have been "banding" or spraying herbicide directly over rows during shredding operations.

"With a mounted spray nozzle on a flail shredder, producers can get good, timely stalk destruction," said Dr. Robert Lemon, Extension state cotton specialist. "Another benefit is inclement weather in the past has prevented producers from getting into the fields with tillage equipment. A lot of them have switched to using herbicide during stalk destruction activities."

In Nueces and San Patricio counties, 75 percent to 80 percent of the acreage has been treated chemically, according to the Texas Boll Weevil Eradication Foundation. Kleberg, Refugio, Victoria and Calhoun counties are also seeing increased use of the technology.

In the upper Coastal Bend and Southern Blacklands regions, approximately 30 percent of the acreage is chemically terminated.

Extension researchers recommend the following management practices:

• Based on field research, the first application of an amine salt formulation should be at the rate of 1 pound of active ingredient per acre (one quart of a 4-pound active ingredient/gallon formulation). Generally, a second application of 0.5 pounds of active ingredient per acre is necessary for control of any live stalks and emerged cotton seedlings.
  Applications should be made with 5 gallons to 15 gallons of water per acre. Surfactant added at a minimum rate of 0.5 percent is recommended.
• Cotton stalks should be shredded 6-8 inches in height and spray application should be made soon after shredding.
• Standing cotton stalks should be sprayed soon after harvest (within 7 days) for optimum control.

An Extension publication, "Cotton Stalk Destruction with Herbicides", can be found on the Web at http://publications.tamu.edu.