Weekly in-season Updates
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INFORMATION |
July 23, 2007 Talkin’ Cotton Lots of Rain, and Lots of Weeds! By Shane Osborne, Oklahoma State University
Regardless of the latest and greatest technological advances in the cotton industry one thing that still plagues cotton farmers is weed problems. Weeds in cotton can rob the soil of both moisture and essential nutrients. Although Roundup Ready Flex cotton varieties (which allow broadcast applications of approved formulations of Glyphosate for most of the growing season, refer to label) have simplified most producers weed control programs new problems continue to emerge. Horseweed (often referred to as mares tail) has quickly become one of many producer’s biggest weed problems across the much of the cotton belt. For the past several years glyphosate-resistant populations of this weed have grabbed many headlines at one time or another in almost every agricultural magazine or newspaper. The fact is that even the plants that do not have true resistance to glyphosate (which currently still happens to be the case for most of Oklahoma) can still be very difficult to control. Cotton Incorporated through the Oklahoma State Support Committee funded a project initiated by Oklahoma State University’s Extension Cotton Program this past spring. Two trial locations were chosen, one in Tillman county on the Roger Fisher farm and one in Washita county on the Doc and Danny Davis farm. Both locations were no-till dryland cotton production systems with heavy populations of horseweed. Data from other regions across the cotton belt suggested that pre-season control was essential to get a clean start and most programs included either 2,4-D or Banvel. Therefore four treatments were applied at each location to evaluate their effectiveness at controlling horseweed. The applications at each location were applied approximately 45 days prior to planting. At the Tillman county location Banvel + Glyphosate + Valor provided excellent control of horseweed. At the Washita location a cover crop was still growing at application timing, therefore the Glyphosate was dropped out of the mix, however, Banvel + Valor was again very effective at controlling horseweed. The key to controlling this particular weed is in the application timing. Typically, very effective control can be achieved when the horseweed is in the rosette stage or just beginning to bolt upward. Most successful applications are made on small horseweed, less than 6 inches tall, but when drought stressed the smaller the better. For detailed information regarding chemical rates and all of the treatments evaluated please call the OSU Southwest Research and Extension Center located in Altus at 580-482-2120 or email me at shane.osborne@okstate.edu. Also we would like to thank the Cotton Incorporated State Support Committee for funding this project as well as our cooperators Roger Fisher and Doc and Danny Davis. Washita County – 2 Weeks after planting 8 oz/A Banvel + 2 oz/A Valor + 0.25% v/v Induce Applied 45 days before planting
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