Issue link: http://read.uberflip.com/i/802944
WWW.POTATOGROWER.COM 25 on glyphosate for weed control, resistant Palmer amaranth (Amaranthus palmeri) began to overrun crops and caused yields to plummet. Today, integrated weed management programs that use a diverse range of controls have become commonplace in cotton, despite the higher cost. Growers are using cover crops, hand-weeding, tillage, weed seed removal and herbicides with different mechanisms of action in order to keep Palmer amaranth at bay. There have been tradeoffs. Additional herbicides, labor and fuel have tripled the cost of weed control in cotton. In addition, increased tillage has raised concerns about soil erosion from water and wind. But for now, the crop has been preserved. "Although diversification is critical to crop sustainability, it can be difficult to make a decision to spend more on integrated weed control strategies," says Stanley Culpepper, a weed scientist at the University of Georgia. "As a result, many of the most successful diversification efforts can be found in crops like cotton where change became an imperative." Culpepper says that in addition to costs, another barrier to adoption of integrated weed management is the belief by some that new types of herbicides will be invented to take the place of those no longer effective on resistant weeds. But the HPPD inhibitors discovered in the late 1980s for use in corn crops are the last new mechanism of action to make its way out of the lab and into the market. "It would be naïve to think we are going to spray our way out of resistance problems," Culpepper says. "Although herbicides are a critical component for large-scale weed management, it is paramount that we surround these herbicides with diverse weed control methods in order to preserve their usefulness—not sit back and wait for something better to come along." This report, originally distributed by the Weed Science Society of America, appeared on www.potatogrower.com on July 15, 2016. Commelina diffusa was the fi rst species reported to display herbicide resistance when Hawaiian sugarcane growers noticed its resistance to a synthetic auxin herbicide in 1957. Photo courtesy Southern Illinois University If growers are to avoid weeds like lambquarter developing resistance to herbicides, they must incorporate diverse weed control programs on their operations. Plants like waterhemp and its weedy brethren may have begun developing resistance to herbicides long before most people realize. WWW.POTATOGROWER.COM 25