Cotton Stalk Destruction – What’s New for 2018
By Corrie Bowen
County Extension Agent
Cotton stalk destruction is a topic of research that has been evaluated for a good 20 to 25 years. Herbicides have been applied to conventional and Roundup Ready Cotton, focusing on the traditional active ingredients such as 2,4-D and dicamba. The gold standard has been applying 1 quart/acre of a 4lb/gallon a.i. 2,4-D amine product immediately afterwards through two weeks after shredding stalks. This practice has yielded better than 90% control for decades.
With an increase in adoption of the dicamba and/or 2,4-D tolerant cotton varieties in 2017 and 2018 and with harvest upon us, chemical selection for cotton stalk destruction is a current topic of discussion. For Enlist, (2,4-D tolerant) cotton, 2,4-D is no longer an option to chemically destroy cotton stalks.
Stalk Destruction Options for Enlist Cotton
For cotton growers with Enlist (2,4-D tolerant) cotton, they will now have the choice of using either dichlorprop or dicamba to control cotton stalks. I received word on July 25th from TDA that a 24(c) Special Local Need label has been approved for a dichlorprop-containing product called Duplosan by NuFarm. ( see attached file). This product will be equally effective on cotton varieties with the XtendFlex or Glytol LibertyLink traits. Data compiled by AgriLife Extension shows that this product will be more effective than dicamba for controlling Enlist cotton. The Duplosan label calls for a use rate of 32-48 fl oz/acre. Make notice that when using Duplosan for cotton stalk destruction, Duplosan should be applied to cotton stalks with some leaf regrowth. Applications of Duplosan made to freshly mowed stalks may be less effective. Please note that Duplosan is an ester formulation, so special care will need to be taken if susceptible plants are nearby as volatilization is likely. Also note that this product is a state limited use pesticide, thus you must be a licensed pesticide applicator or be working under the direct supervision of a licensed applicator to purchase or apply this product. What does Duplosan cost per acre? I did a little research, getting quotes from only two local distributors. Approximate cost is $39.60 per gallon. With the labeled use rates, this equates to $9.90 to $14.85 per acre for Duplosan.
Stalk Destruction Options for Xtendflex Cotton Varieties
For Xtendflex (dicamba tolerant) cotton varieties, the old gold standard of 2,4-D amine is still a valid option for cotton stalk destruction, costing generally less than $5.00 per acre for 2,4-D amine. 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. The first application should be at the rate of one pound of active ingredient per acre (for example, 1 quart of a 4 lb/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 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 2010 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. We also know from previous research that waiting 21 days after shredding cotton stalks has not been as effective with 2,4-D.
2,4-D Application by Ground Application allowable September 1, 2018
The Texas Department of Agriculture has granted the suspension of a rule regarding the application dates of 2,4-D in Wharton County – Section 7.53(oo)(1) and (2) of the special provisions for Wharton County of the Texas Pesticide Laws and Regulations. The suspension allows for the ground application of 2,4-D and 2,4-D containing herbicides by permit on the west side of the Colorado River in Wharton County beginning on Saturday, September 1, 2018. Ground applications of 2,4-D on the east side of the Colorado River in Wharton County are already permissible under rule 7.53(oo)(1). All other applicable rules for Wharton County continue in effect. Pesticide applicators are urged to pay special attention to 7.53(oo)(4) “In no case shall 2,4-D be used to treat any area that is nearer than two miles to any susceptible crop”. Pay close attention that this rule suspension granted by TDA only allows the application of 2,4-D by ground application only beginning September 1st. The aerial application of 2,4-D in Wharton county continues to be prohibited until September 15th on the east side of the Colorado River and until October 1st on the West side of the Colorado River. Also note in rule 7.50 (b) (3) that the use of any turbine or blower-type ground application equipment to apply regulated herbicides is prohibited.
Also, in a regulated county such as Wharton County, no person shall spray regulated herbicides (2,4-D, dicamba, MCPA, or quinclorac) when the wind velocity exceeds 10 miles per hour or as specified on the product label, if the label is more restrictive. Regulated Herbicide Spray Permit applications are available at the Wharton Co. Extension Office, or by logging-on at http://texasagriculture.gov/Portals/0/forms/PEST/Applicator/spraypermitq820.pdf
TDA Pesticide license holders are required to submit a regulated herbicide spray permit when 2,4-D, dicamba, MCPA, or quinclorac will be sprayed in a regulated county. The submission of the regulated spray permit pertains to 2,4-D, but also when spraying dicamba, MCPA, or quinclorac in Wharton County. Completed Regulated Herbicide Spray Permit applications can be faxed to the TDA Regional Office in Houston at (888) 223-5606.
Corrie Bowen, MS
County Extension Agent – Agriculture
315 E. Milam, Suite 112
Wharton, Texas 77488