As cotton harvest nears completion it is important not to forget about destroying cotton stalks as soon as the crop has been removed from the field to aid in reducing costs for the Boll Weevil Eradication Program (BWEP). 

This year we’ve seen a 99 percent reduction in the number of boll weevils caught in the zone, with only one weevil caught in Nueces County and only 108 boll weevils caught in the entire zone—564,000 acres of cotton.

The cotton stalk destruction deadline for Nueces County remains September 1, 2011.

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.

Many growers use reduced tillage systems, which do not allow for primary tillage operations, causing producers to evaluate new methods for stalk destruction.

Consequently, we see a lot of interest in alternative cotton stalk destruction throughout South Texas. While many producers still use various tillage methods to destroy cotton stubble, be aware that other choices are available. Regardless of the method, the primary purpose of destroying cotton stalks is the removal of both feeding and fruiting sites that may be used by the boll weevil to reproduce.

Several herbicides are registered for cotton stalk destruction, including but not limited to: 2, 4-D (ester and salt formulations); several dicamba products (Weedmaster, Clarity, Banvel); and Harmony Extra (thifensulfuron-methyl + tribenuron-methyl). For these 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 active ingredient per gallon formulation). Generally, a second application of 0.5 to 1.0 pound active ingredient per acre will be necessary for control of any live stalks and emerged cotton seedlings.

To obtain optimum results, cotton stalks should be shredded (6- to 8-inch height) and application should be 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 are banding the herbicide during the shredding operation, and achieving excellent results.

Note that 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 per100 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 stalks left standing.

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

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