The highly invasive weed Cogon Grass

Imperata cylindrica, or most commonly known as ‘cogon grass’, is in the Top 100 Invasive Species list, according to the Invasive Species Specialist Group (ISSG) and in the Top 10 Worst Weed species in the world. This weed is native to Japan and Southeast Asia and has been introduced around the world through several ways, including as forage for cattle ranchers and packaging material from Japan. It is currently found in Southeastern US (mostly in Florida) and areas with humid tropics conditions.

figure-1_edd-map-of-the-distribution-of-cogon-grass-in-southeast-us

Figure 1: EDD map showing the distribution of Imperata cylindrica in southeast US.

This weed can grow in nutrient poor soils without much effort as it has the ability to absorb nutrients more effectively compared to other plants (Inderjit and Dakshini, 1991). This leads to natives plant having less nutrients (such as nitrogen) and hence hindered development. It also affects the biodiversity of an area as less native species can grow and their survival chances decrease.

One can say that its removal might be easy by uprooting them or burning them. These methods could work for other invasive species but not for the cogon grass. This weed has the capacity to adapt to fire regimes and in fact grows well in disturbed habitats. If we would burn an area and rely on the available seed bank to repopulate the area, it would be counter-productive as the cogon grass would be among the first plants to sprout back. Hence, by the time other species would be developing, this weed would already be well developed (Lippincott, 2000) and already absorbing much of the nutrients in the soil, leaving little for the native developing plants. If we decided to uproot these, their seed would be dispersed more easily and lead to more damage than benefits.

One way to manage them might be by using species-specific herbicide (Ramsey et al., 2003), but their rhizome network might become dormant and still be viable for a long time. Hence, there are no true solution to manage this highly invasive weed.

References

Early Detection and Distribution Mapping System (EDDMapS). 2009. Cogongrass: Imperata cylindrica (L.) Beauv.

Inderjit and Dakshini. 1991. Investigations on some aspects of chemical ecology of cogongrass, Imperata cylindrica (L.) Beauv. Journal of Chemical Ecology. 17(2):343-352.

Invasive Species Specialist Group. 2010. Imperata cylindrica. Reviewed by: Dr. James Leary, Department of Natural Resources and Environmental Management, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa.

Lippincott CL. 2000. Effects of Imperata cylindrica (L.) Beauv. (cogongrass) invasion on fire regime in Florida sandhill (USA). Natural Areas Journal. 20(2):140-149.

Ramsey et al. 2003. Cogongrass [Imperata cylindrica (L.) Beauv.] response to herbicides and disking on a cutover site and in a mid-rotation pine plantation in southern USA. Forest Ecology and Management. 179(1-3):195-207.

Mohammad Arshad Imrit

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