Beware of Cogon Grass
Cogon grass (Imperata cylindrica) is an invasive, non-native
grass which occurs in Florida and several other southeastern
states. A pest in 73 countries, and considered to be one
of the "Top 10 Worst Weeds in the World", cogon
grass affects pine productivity and survival, wildlife habitat,
recreation, native plants, fire behavior, site management costs
and more.
Identifying Cogon Grass
How
to Recognize Cogon Grass |
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Cogon grass is a tall (2-5 ft.) perennial
grass with bright yellowy-green foliage. The leaf blades have
a midvein which is clearly offset to one side, and serrated
(toothed) edges. The rhizomes are hard, scaly, and cream-colored
with sharply pointed tips. The seed head is fuzzy, white, and
plume-like (see images above).
Cogon
grass invasion in Central FL upland pine sites |
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Common Locations for Cogon Grass
Cogon grass is found on roadsides, mining sites,
borrow pits, and other areas of soil disturbance, and is able
to invade moist to dry upland pine sites, Following initial
invasion, cogon grass often forms dense, field-like monocultures.
Cogon grass spreads readily on disturbed sites and through
movement of soil contaminated with small pieces of rhizome
or seed (often due to site disturbance in timber harvest,
site preparation, road grading, use of contaminated fill dirt,
etc.). Cogon grass infestations can reduce pine survival and
growth, and in fire situations, may result in complete mortality
of overstory trees due to flammable oils in the grass blades
raising the intensity and severity of prescribed burns. Over
time cogon grass may significantly impact management and productivity
of pines on infested sites.
Aerial view of expanding cogon grass infestation (light
and green colored patches) following harvest of timber
stand in NW Florida.
Image courtesy of Greg Leach, International Paper |
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Decreased pine growth and survival in
cogon grass-infested portions of pine plantation. |
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Regulatory Status
Due to the damaging effects of cogon grass invasion, cogon
grass is listed as a noxious weed by both the state and federal
levels. See list of regulations and ordinances.
Some Treatment Recommendations
Prevention
Avoid soil disturbance, timber harvest, fire,
etc. unless as a part of a specific treatment regime. Always
clean equipment after operating in infested areas.
Mechanical/Cultural
Mow or prescribed burn prior to herbicide
application to remove built-up thatch and promote active growth
herbicide uptake. Do not mow when seedheads are present. Do
not burn without a follow-up herbicide treatment.
Chemical
Allow 12 inches of re-sprout before
applying herbicide.
Most managers recommend a foliar application of 2% glyphosate
(eg. Roundup/Accord), or 1-1.5% imazapyr (eg. Arsenal/Chopper)
(be aware of soil activity), or a tank mix of the two herbicides. Apply
herbicide by spraying all foliage just until wet to the point
of run-off. Links to Identification and Control Guides.
Timing
If you can only do one treatment a year, apply your
treatment in the fall before the first frost. Otherwise,
re-treat regularly whenever adequate foliar re-sprout has
occurred.
Integrated
treatment of cogon grass (herbicide & fire) |
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