Miller, James H.; Manning, Steven T.; Enloe, Stephen F. 2010. A management guide for invasive plants in southern forests. Gen. Tech. Rep. SRS–131. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 120 p.
Cogongrass [Imperata cylindrica (L.) P. Beauv.] and the closely related native, Brazilian satintail (I. brasiliensis Trin.), are aggressive, colony-forming dense erect perennial grasses 1 to 6 feet (30 to 180 cm) in height. Hybridization is probable and makes differentiation difficult. Both have tufts of long leaves hiding short stems, yellow-green blades (each with an offcenter midvein and finely saw-toothed margins), and silver-plumed flowers and seeds in spring (sporadically year-round). Seed are dispersed by wind and on contaminated clothing, equipment, and products like pinestraw mulch and fill materials. Seed viability appears at this time to be significantly less in northern Florida and southern Georgia and higher in southern Alabama and Mississippi. Dense stands of dried plants remain standing during winter to present a severe fire hazard, while remaining green year-round in central and southern Florida. These species burn hot even when green.
Infestations form dense rhizome mats making eradication difficult, because abundant shoot and rhizome buds usually sprout after treatment or lay dormant to sprout within months. Rhizomes are sharp tipped and can pierce roots of other plants. Older infestations will be more difficult to control than new invasions that occur as circular patches.
Both species are Federal and State noxious weeds, while red-tipped cultivars are still sold and planted in many Southern States. These cultivars, bred for cold hardiness, have viable pollen that might spread to the invasive cogongrass plants. Red cultivars can revert to the green aggressive type. Some Southern States prohibit the sale of the red cultivars. Visit www.cogongrass.org and other State cogongrass Web sites for more details. Resemble Johnsongrass [Sorghum halepense (L.) Pers.]; purpletop [Tridens flavus (L.) Hitchc.]; silver plumegrass [Saccharum alopecuroidum (L.) Nutt.]; and sugarcane plumegrass [S. giganteum (Walter) Pers.]—all having a stem, do not produce fluffy seed heads, and no sharp-tipped rhizomes jutting up from the soil surface. Also resemble longleaf woodoats [Chasmanthium sessiliflorum (Poir.) Yates] that occurs in shaded colonies in forests but lacks offcenter midveins and silky flowers having tufts of spiked flowers and seeds along a slender stalk.
Management strategies
- Do not plant the red-tipped cultivars (Japanese bloodgrass and Red Baron). Remove prior plantings, and control sprouts and seedlings.
- Treat when new plants are young and located through frequent surveillance of lands in infested zones.
- Minimize disturbance within miles of where this plant occurs, and anticipate wider occupation when plants are present or adjacent before disturbance.
- Repeated cultivation and planting of aggressive grasses or herbicide resistant crops can restore pastures and croplands.
- Burning and bush-mowing treatments can remove standing plants for more efficient herbicide treatments. However, burning usually causes rapid infestation expansion and can kill native shrubs and trees that constrain spread.
- Do not use or transport fill dirt, rock, hay, or pinestraw from infested lands.
- Seed production can be stopped by mowing, burning, or herbicide treatments in early stages of flowering or even shortly before flowering. However, these treatments can prompt later flowering/seeding as well.
- Clean seed and rhizomes from equipment and personnel working in infestations before leaving the infested site.
- Forage quality is low, eaten only when shoots are young and tender by horses, goats, sheep, mules, and some cattle.
Recommended control procedures
- Thoroughly wet all leaves with one of the following herbicides in water with a surfactant when grass is actively growing and at least 1to 2 feet high or older growth from June to September: Chopper Gen2* as a 2-percent solution (8 ounces per 3-gallon mix) or Arsenal AC* as a 1-percent solution (4 ounces per 3-gallon mix). Repeat applications in subsequent years may be required for eradication. A glyphosate herbicide may be tank mixed as a 2- to 5-percent solution with Chopper Gen2* at 2 percent (8 ounces per 3-gallon mix) or Arsenal AC* at 1 percent (4 ounces per 3-gallon mix). This treatment will accelerate burndown of actively growing shoots but may not improve rhizome kill.
- When safety to surrounding vegetation is desired (especially hardwoods, shrubs, and pines), apply a glyphosate herbicide as a 2- to 5-percent solution (8 to 20 ounces per 3-gallon mix). Two applications per growing season (just before flowering in spring and again in late summer to regrowth) are typically necessary. Apply in successive years when regrowth is present until no live rhizomes are observed for eradication; at the same time promote or establish desirable plants.
* Nontarget plants may be killed or injured by root uptake.
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