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Cotton specialist cautions growers on herbicide drift

J. C. Banks, Oklahoma State University cotton specialist, cautions farmers to be aware of the potential for herbicide drift and its detrimental effect on broadleaf crops, particularly young cotton plants.

“As cropping systems change, producers need to be aware of the potential for drift of pasture and summer fallow herbicides to susceptible crops. All broadleaf plants are susceptible to phenoxy herbicides, but cotton is one of the most sensitive to drift rates of these chemicals.

“These phenoxy or hormone type herbicides include 2,4-D, dicamba, picloram, triclopyr and clopyralid as active ingredients. Many trade names contain these ingredients, so it is a good idea to evaluate the active ingredients as you decide on materials to purchase,” Banks said.

Herbicide labels, usually just below the trade name, include a section stating active ingredients and the percentage of each.

“Look for 2,4-D, dicamba, picloram, triclopyr or clopyralid as the active ingredients, and if present, be very careful when applying the chemical if cotton or other susceptible crops are in the vicinity,” Banks said. “In some Oklahoma counties applying a herbicide with any of the above active ingredients requires a form be sent to the Oklahoma Department of Agriculture stating intent to apply the herbicide or mixture and the location of the application. Within seven (7) working days following the application a report is required to be filed to ODA with the requested application information.

“Any wind, even a light breeze can move small droplets of chemical many hundreds of feet, and under windy conditions, movement can be up to several miles. If you are spraying near a cotton field, time the spray when the wind is blowing away from the cotton,” Banks said.

“Use lower pressure and drift reduction nozzles to ensure the material lands on the target and is not carried by the wind.”

Some materials are formulated as esters instead of amines and these will not only drift but vapor can move from the application site for several days following application. During the growing season of a sensitive crop, only amine formulations should be used.

Banks also warns about off-site movement of phenoxy herbicides in contaminated spraying equipment. The herbicide becomes bound to plastic in solution tanks and rubbers hoses of the boom. It is almost impossible to completely clean these herbicides from a sprayer.

“Stainless steel tanks can be cleaned, but all rubber components of the boom should be changed to avoid contamination of the spray,” Banks said. In many cases 2,4-D is extracted from boom hoses and contaminates hundreds of acres of cotton.

“The Oklahoma Department of Agriculture, Food and Forestry maintains a website for growers to post locations of sensitive crops and for applicators to evaluate an area prior to application. Check

Specific areas can be located on a state map, and a zoom feature can locate the area for application. If an isolated field of cotton or a grape vineyard is not on the map, it can be added. ODAFF now has identified the hormone herbicide restricted areas on the Pesticide Sensitive Location Viewer.

“All applicators should take precautions to avoid harming sensitive crops when they apply herbicides. Legally, the applicator is always responsible for off-site movement of herbicides,” Banks said.

In addition to economic injury to the crop, damaged relations with neighbors often result from misapplication. Applicators can avoid the problem by taking a few precautions.

NTOK Cotton is a cotton industry partnership that encourages increased cotton production on the Rolling Plains of North Texas, Oklahoma and Kansas.

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