Palmer amaranth is making its way into fields across the Midwest, threatening crop systems and severely reducing yield if not controlled early.
Palmer amaranth is a highly competitive weed that can produce seeds at a tremendous rate — ranging from several hundred thousand to more than a million seeds per plant, according to a recent study from the University of Illinois. A few surviving female plants can produce enough seeds to alter the weed spectrum of any field. Its rapid seed production has contributed to its spread north.
“Palmer amaranth is moving northward and is a serious threat to corn fields and should be on the radar of growers throughout the Midwest,” says Scott Ditmarsen, field scientist, Dow AgroSciences. “The key to managing Palmer amaranth is to identify it early and utilize an aggressive weed management program, including tillage, multiple herbicide applications with multiple modes of action, and physical plant removal.”
According to the University of Illinois study, Palmer amaranth seed has a higher germination rate than most other Amaranthus species, including waterhemp. Left untreated, this invasive weed can devastate a crop’s yield.
“Palmer amaranth is unique because of its rapid growth,” Ditmarsen says. “It can grow several inches per day, making it extremely competitive among corn crops. Along with its ability to grow rapidly, Palmer amaranth also has an extended germination period that spans from early spring through late summer, which requires growers to actively scout for it throughout the season.”
According to WeedScience.org, Palmer amaranth is resistant to five different herbicide classes, with multiple resistance found in many states, including Nebraska, Georgia, Tennessee and Kansas.
“Due to its increasing herbicide resistance, growers should implement a season-long management plan using multiple herbicides that work on different sites of action,” Ditmarsen says. “Targeting different sites of action is key to managing and preventing the spread of herbicide-resistant weeds such as Palmer amaranth.”
According to 2012 Stratus data,1 13.3 percent of growers in 31 corn- and soybean-growing states reported the presence of glyphosate-resistant Palmer amaranth on their farm, which is up from 8.7 percent in 2011. Meanwhile, upward of 75 percent of growers in Southern states reported glyphosate-resistant Palmer amaranth on their farm in 2012.
There are ways to control Palmer amaranth and prevent it from spreading. According to Brittany Loewen, U.S. corn herbicide product manager, Dow AgroSciences, SureStart herbicide is an effective tool featuring three non-glyphosate modes of action that are necessary to control Palmer amaranth prior to planting.
“Because Palmer amaranth can have a tremendous impact on yield potential, it is important to stay one step ahead of it,” Loewen says. “Using SureStart herbicide in a two-pass program is an effective way to control this aggressive weed and give corn a clean start.”
For more information on controlling Palmer amaranth, visit GetMoreTime.com.
1Stratus Agri-Marketing Inc. Glyphosate Resistance Tracking USA 2012.