Who is This Invader? Let’s Talk About Cogongrass
Scientific name: Imperata cylindrica
Common names: Japanese bloodgrass, Red Baron grass (red varieties), Cogongrass, Cogon grass, japgrass, bloodroot grass.
Have you ever seen cogongrass? Even if you do not know, you likely have as it is one of the most prominent weeds in Marion County. Not only is it prevalent here, it is the world’s seventh worst weed and considered a noxious invasive weed, meaning it is not native and can cause harm to other species. (United States, 2014). Thought to be originally from southeast Asia, cogongrass is now present throughout tropical and subtropical regions of the globe including much of the southeastern US, covering almost 500 million acres worldwide. It was actually introduced intentionally to Florida in the 1930s to control erosion and as a forage crop (Cogongrass, n.d.). It was also utilized as packing material and introduced earlier to Louisiana in 1912. Today, it reduces forest productivity, destroys wildlife habitat (including those for gopher tortoises, Eastern Indigo snakes, and some birds), encroaches in pasture and hay fields, displaces native and desirable vegetation, affects roadways, and is a poor forage crop. It also acts as a fire hazard since it can grow well in fire prone areas and burn very hot if ignited, even when green (United States, 2014, Holmes, 2018). It is important to know about this weed including its characteristics and methods of control so it can be managed and eradicated where possible.
Cogongrass is a perennial rhizomatous grass that grows in tropical and subtropical regions. It does well in a variety of soils including fine sand to heavy clay and low fertility. It grows in bunches up to four feet high with light green leaves that display an off-center mid-rib and finely serrated margins. These serrations as well as roughness and high silica content of the leaves make the grass undesirable as forage to livestock. It can grow well in full sunlight as well as partial shade. The leaves can become brown if they are older or subjected to frost, which results in a fire hazard. In the Spring, it develops long, fluffy, white seed heads with as many as 3000 seeds. It can initiate flowering outside of this timeframe in response to some disturbance such as mowing, herbicide application, and the first hard frost, but it is unsure whether or not it spreads via seed. It definitely can spread via rhizomes. While one can see the grass on the surface, much of the plant exists underground in sharply pointed rhizomes that can extend 48inches into the soil, far beyond where visible above ground. (Imperata, n.d., Holmes, 2018, United States, 2014)
The persistence and prevalence of cogongrass can make it difficult to control. Once it establishes itself, it can be hard to remove it. Nevertheless, there are some ways that this weed can be eradicated and prevented through dedicated efforts. The two main methods of control are herbicides and cultivation. In order to fully eradicate it, the rhizomes have to be destroyed. Pesticides such as prometon (Pramitol), tebuthiruon (Spike), imazapyr (Arsenal), and glyphosate (Roundup) can be used, but caution should be taken to not damage other crops (Imperata, n.d.). It is best to apply herbicides in the Fall prior to frost. In addition to pesticides, discing or plowing the area several times during the dry season can also help to kill this weed. It is important to cut to a depth of at least 6inches to insure adequate breakage of the rhizomes (Imperata, n.d.). A combined approach with careful management over the course of months is the best way to successfully eradicate the weed. In addition to control of current weed infestations, prevention its introduction to new areas is also important. Be mindful of cleaning equipment, vehicles, clothing, etc. that were used on cogongrass, and do contaminated areas last (United States, 2014).
Cogongrass is definitely a problematic weed that plagues many pastures and other areas in Marion County. Not only does it displace native species and take over viable pastureland, it also can pose a danger as a fire hazard. Through understanding it’s characteristics and control methods, it can be better understood how to identify and eradicate this nuisance to improve our pastures and other areas for our livestock and community.
Imperata cylindrica. (n.d.) UF IFAS University of Florida Center for Aquatic and Invasive Plants. https://plants.ifas.ufl.edu/plant-directory/imperata-cylindrica/
United States Department of Agriculture. (2014). Cogongrass Help Needed to Destroy This Nuisance Weed in Alabama [Brochure]. U.S. Department of Agriculture. https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs141p2_021449.pdf
Holmes, D. (2018, June 13). Learn to Control Cogongrass. UF IFAS University of Florida Blogs. http://blogs.ifas.ufl.edu/marionco/2018/06/13/learn-control-cogongrass/
Cogongrass. (n.d.). USDA National Invasive Species Information Center. https://www.invasivespeciesinfo.gov/terrestrial/plants/cogongrass