Invasive Species background from ACES.
“Cogongrass (Imperata cylindrica) has become a major problem for landowners, land managers, foresters, and governmental agencies since its introduction into Alabama. Known to many as “Japan grass,” cogongrass was accidentally introduced into Alabama near Grand Bay about 1911 as seed in packing materials from Japan”
“Native to Asia and introduced into the Mobile area in early 1900s. This tall perennial grass with yellowish foliage forms dense circular infestations that exclude all native species and has no known uses. It is highly flammable and poses a severe fire hazard. Over half of Alabama’s counties have cogongrass infestations with the most severe being in the southern tier of counties. Cogongrass is steadily spreading northward by windblown seeds, movement of contaminated fill dirt, and probably through horticultural plantings (commercial red variety) as well as hay, pine straw, and straw sells from infested areas. This is a federal and Alabama State listed noxious weed. Successful eradication is achieved with multiple herbicide treatments over several years.”
For more info go to Cogongrass Management FAQ for good info on how and when to kill it.
Cogongrass Control Recommendations by the University of GA – Includes info on Rehab after killing.
Control Methods from MSUES
Currently, there is no single treatment that effectively eliminates cogongrass infestations. Roundup Ultra, Roundup Pro, or other brands of glyphosate (41% active ingredient formulations) at 5 quarts per acre or as a 1.5% solution will suppress cogongrass. Repeated applications each year for several years are needed for control. Applications of Arsenal, Imazapyr, Polaris, or Habitat (2 pounds imazapyr per gallon formulation) at 48 ounces per acre can be used in certain areas and provide excellent control up to 1 year after application. Because Arsenal and Roundup are nonselective, applications may damage nearby desirable vegetation. Since Arsenal remains in the soil for long periods, its effectiveness on cogongrass and other plants may continue up to a year after application. Do not apply imazapyr herbicides within two times the dripline of any desirable vegetation.
Imazapyr – The active ingredient, imazapyr, inhibits the plant enzyme AHAS (acetohydroxyaced synthase). Habitat is a systemic herbicide that is effective on post-emergent floating and emergent aquatic vegetation. Imazapyr is effective at low-volume rates and does not contain heavy metals, organochlorides or phosphates, making it safe to humans and livestock. Habitat requires the use of a spray adjutant when applying on post-emergent vegetation. Common trade or product names include but are not limited to:
From https://bugwoodcloud.org/mura/cogongrass/assets/File/basffactsheet.pdf: Arsenal AC also fits well into forestry re-vegetation systems- both crimson clover and bahiagrass were found to thrive in areas previously infested with cogongrass that had been treated with Arsenal AC.