What is in this article?:
• Cogongrass has been called “the weed from hell” and “the mother of all invasive species.”
• It is so aggressive, if left unchecked it can replace an entire ecosystem.
• Mississippi has just finished the first year of spraying in a $1.1 million suppression program, while Alabama has a $6 million-plus eradication program in progress.
Important identification feature
John Byrd, Jr., Mississippi Extension professor of weed science, says one of most important identification features of cogongrass is that it blooms in the spring.
“It grows during summer, but unlike other warm season grasses, except zoysia, it blooms immediately after it turns green for summer growth, and then forms white, fluffy seedheads.”
Another identification feature is its rhizome system. “Johnsongrass has rhizomes, but cogongrass rhizomes are far more extensive and numerous,” he says. “Each of the many nodes on a rhizome is capable of producing roots and a new plant above ground. Over 60 percent of the plant’s biomass is in roots and rhizomes, and that’s what you have to kill to completely eradicate a population.”
Two products are available for use in a control program, Browning notes — glyphosate (Roundup ProDry) and imazapyr (Arsenal Powerline and Chopper). Recommended rates for foliar application, he says, vary from 2 percent to 3 percent glyphosate product to 1 to 1.5 percent Arsenal products.
“You can safely use Arsenal around pine trees and it will hammer cogongrass,” he says. “I prefer a mixture of 1.5 percent solution of Roundup with 1/2 percent to 1 percent of Arsenal and a good surfactant, which gives a good synergistic response.
“Be aware, though, you can’t use this mixture around hardwoods; in those areas, you’ll have to use only a glyphosate product. It will take more applications, but over a period of time you can take out the grass. The more you can do to cogongrass, the more control you’ll get.”
Jim Hancock says the Mississippi spray program isn’t using the herbicide mixture. “We feel we get a more permanent kill with the Arsenal products. We use a 2 percent solution and spray enough to thoroughly wet the plants.”
In agricultural or pasture environments, disking the ground will put additional stress on the cogongrass, Browning says. “Deep disking will knock it back; continued deep disking will really hamper it. If you can mow or burn the grass, come back and disk, then let it sprout back up and apply herbicide, it will be more effective than just one spray application or one technique alone.
“But, you have to be vigilant in going back to see how well the herbicide applications have worked and which areas you may have missed. In one field that was sprayed three times with Roundup, there were still spots coming back. So, you may have to spot treat over two or three years. Be sure to spray 6-8 feet beyond visible cogongrass to get any tillers.”
Charles Bryson, USDA/ARS botanist, says cogongrass is similar in invasiveness to kudzu. “It has not yet reached the level of importance of kudzu, but has potential to spread and become as bad or worse than kudzu.”
In 1948, Browning says, Weed Scientist R. L. Pendleton warned, “Steps should be taken at once to completely eradicate this noxious weed from the Western Hemisphere.”
“Now, in the 21st century, we’re behind the curve,” he says. “It’s time to get busy working on stopping this pest. Fortunately, a lot of groundwork through Mississippi’s Bureau of Plant Industry and the Mississippi Department of Agriculture and Commerce.