Weeds need watching in newly planted cotton

Weeds need watching, says J.C. Banks, Oklahoma State University Extension state cotton specialist.

“Cotton planting is essentially complete in irrigated areas and is well underway in dryland areas. Most early planted cotton is up to a good stand, but not growing rapidly due to a lack of heat and sunshine. I have been observing a few fields with wet weather blight on leaves and some disease lesions on roots, but warm weather should turn the cotton around and it should grow out of the early problems.

“The cooler weather that slows cotton growth also favors weed growth. We are learning the value of a yellow pre-emergence herbicide, even when we are in a Roundup Ready program. The wet weather has not allowed timely spraying of Roundup and weeds are growing much faster than the cotton,” Banks says.

“One weed problem that is much worse this year is horseweed (mares tail), which can be managed when it is small, but when it gets over six inches tall, it is difficult to kill. It is especially difficult in no-till conditions if it was not controlled prior to planting. The best control programs have involved phenoxy herbicides alone or tank mixed in early to mid-April, about one month prior to planting. At planting or soon after planting, a treatment of Roundup will usually control the small weeds before they get large enough to be difficult.

“Continued Roundup treatments in the summer should be as needed when weeds are small. If the weeds (especially horseweed) are over six inches tall, the maximum-labeled rate of Roundup should be used. Be sure to condition the spray solution with ammonium sulfate prior to adding the Roundup and set spray boom height and pressure to obtain maximum deposition on the weeds.

“For morningglory control in irrigated areas, Staple has been effective, but wait until after the water furrows are made to avoid moving an untreated layer of soil on top of a band of Staple.”

Texas Rolling Plains

Billy Warrick and Chris Sansone, Texas A&M University Extension agronomist and entomologist, respectively say almost 50 percent of the Rolling Plains cotton is now planted and should be completed in two weeks. Good soil moisture and favorable temperatures are helping cotton establish a stand in less than seven days. Seedling cotton is looking good with minimal thrips damage.

Most producers are using seed treatments that provide control early in the season. Weeds are being controlled either mechanically or chemically to allow the crop to establish without competition. Cotton acreage in the area, they say, is close to normal with a slight increase in grain sorghum acreage. Wheat is still drying down and harvest is beginning on a limited basis.

To contact these scientists: Warrick and Sansone telephone is (325) 653-4576 at San Angelo, Texas. Banks’ telephone is (580) 482-2120 at Altus, Okla.

Email addresses are: [email protected]; [email protected]; [email protected].

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