As cotton harvest continues, it is important to remember to destroy cotton stalks as soon as the crop has been harvested to aid in reducing costs for the Boll Weevil Eradication Program (BWEP). This year the number of boll weevils caught in the zone has been 90 percent less than last year.

The Chairman of the Zone 2 Cotton Producer Advisory Committee has sent a request to the (Texas Department of Agriculture (TD) to extend the cotton stalk destruction deadline for Zone 2, Areas 1, 2 and 3. Citing weather conditions that delayed cotton planting at the beginning of the season, along with seasonal weather that delayed crop maturation, the committee chairman is requesting the deadline for these areas with a September 1 and September 15 deadline be extended to September 22, 2010. This change will be in effect for the 2010 crop year only.

Counties affected by the extension include: Jim Wells, Kleberg, Nueces, San Patricio, Duval, Webb and the southern portions of Bee, Live Oak and Aransas counties.

In its native habitat cotton is a perennial shrub that may survive for many years. The perennial habit of cotton allows it to re-grow following harvest, providing the potential for development of hostable fruit (squares and bolls) for boll weevil feeding and reproduction. Under good environmental conditions, cotton plants can generate hostable fruit in three to four weeks.

When field conditions and weather are favorable for tillage, stalks can be shredded and then disked to destroy the intact plant. Stubble stalk pullers can also be used to uproot the stalk. These mechanical methods are generally successful, but some stalks may survive these operations. Also, many growers are implementing reduced tillage systems, which do not allow for primary tillage operations, causing producers to evaluate new methods for stalk destruction.

There has been much interest in alternative cotton stalk destruction throughout South Texas in recent years. While many producers still use various tillage methods to destroy cotton stubble, other choices are available. Regardless of the method, the primary purpose of destroying cotton stalks remains the same –removing both feeding and fruiting sites the boll weevil may use to reproduce.

Several herbicides have been registered for cotton stalk destruction, including but are limited to: 2,4-D (ester and salt formulations), several dicamba products (Weedmaster, Clarity, Banvel), and Harmony Extra (thifensulfuron-methyl + tribenuron-methyl). For products to be legal for cotton stalk destruction, the label must contain a section addressing “crop stubble” or specify cotton as the target pest following harvest.

Based on most recent field research, it appears the low-volatile, amine salt formulations are equally as effective as the ester formulations for cotton stalk destruction and minimize problems associated with off-target drift. The first application should be at the rate of one pound of active ingredient per acre (for example, 1 quart of a 4 pounds of active ingredient per gallon formulation). Generally, a second application of 0.5 to 1.0 pound active ingredient per acre will be necessary to control live stalks and emerged cotton seedlings.

To obtain optimum results, cotton stalks should be shredded (6 to 8 inch height) and the spray application made soon after shredding. Best results are achieved if the herbicide is applied the same day as the shredding operation.

To achieve optimum effectiveness, some growers have mounted spray booms directly on their flail shredders and banding the herbicide during the shredding operation, and achieving excellent results. Thorough coverage is essential, and should be in the range of 5 to 10 gallons of water per acre. Also, the addition of surfactant at the rate of 0.5 percent v/v (2 quarts per 100 gallons of water) is recommended. In a recent study conducted at the Texas AgriLife Research and Extension Center, there was essentially no difference in killing re-growing cotton plants with 2,4-D between treating shredded stalks or those or left standing.

If one uses a hormone herbicide like 2,4-D, there is always the potential for off-target drift that might affect other susceptible crops in the area, so be careful and monitor local environmental conditions that could promote the off-target movement of the product.

As we work to wrap up another cotton harvest, it is important to remember that without an effective cotton stalk destruction program in South Texas, boll weevil eradication cannot be accomplished.