NATIVE
RANGE
Southeast Asia, Philippines, China, and Japan
DESCRIPTION
Cogon grass is a perennial,
rhizomatous grass that grows from 2 to over 4 feet in height. The leaves
are about an inch wide, have a prominent white midrib, and end in a sharp
point. Leaf margins are finely toothed and are embedded with silica crystals.
The upper surface of the leaf blade is hairy near the base; the undersurface
is usually hairless. The flowers are arranged in a silvery, cylindrical,
branching structure, or panicle, about 3-11 inches long and 1½ inches
wide.
ECOLOGICAL THREAT
Cogon grass can invade
and overtake disturbed ecosystems, forming a dense mat of thatch and leaves
that makes it nearly impossible for other plants to coexist. Large
infestations of cogon grass can alter the normal fire regime of a fire-driven
ecosystem by causing more frequent and intense fires that injure or destroy
native plants. Cogon grass displaces a large variety of native plant
species used by native animals (e.g., insects, mammals, and birds) as forage,
host plants and shelter. Some ground-nesting species have also been known
to be displaced due to the dense cover that cogon grass creates.
DISTRIBUTION
IN THE UNITED STATES
Cogon grass is distributed throughout the south
and southeastern United States as far west as eastern Texas. There have
been reports of cogon grass surviving as far north as Virginia, West Virginia
and Maryland.
HABITAT IN THE UNITED STATES
Cogon grass
is a hardy species, tolerant of shade, high salinity and drought. It can
be found in virtually any ecosystem, especially those experiencing disturbance. Cogon
grass has been found growing on sand dunes in the southeast, along roadsides,
forests, open fields, and up to the edge of standing water.
BACKGROUND
Cogon grass was introduced
to the United States both accidentally and intentionally. Cogon grass
was first introduced to the U.S. at Mobile, Alabama, via shipping crates
that contained cogon grass as a packing material. It was also brought in
and distributed by the U.S.D.A. for use as a forage grass and for soil erosion
control. Cogon grass is also sold by the nursery trade as an ornamental grass,
valued for its attractive foliage and hardiness.
BIOLOGY & SPREAD
Cogon
grass reproduces both vegetatively and from seed. A single plant can
produce several thousand very small seeds that may be carried great distances
by the wind. Vegetative spread of cogon grass is aided by its tough and massive
rhizomes that may remain dormant for extended periods of time before sprouting. Rhizomes
of cogon grass may be transported to new sites in contaminated fill dirt
or by equipment used in infested areas.
MANAGEMENT OPTIONS
An integrated approach
to cogon grass management, including chemical, mechanical and cultural methods,
is necessary to achieve successful, long lasting control. Effective
management of cogon grass has been achieved by the following combined mechanical-chemical
protocol. First, the infested area is mowed in late spring to remove last
year’s growth and the accumulated thatch layer. About six to eight weeks
later, when about eighty percent of the cogon grass has resprouted to a height
of 6-12 inches, the site needs to be disced as deeply as possible. [Discing
may not be possible in all areas, due to the sensitive nature of some ecosystems].
When adequate regrowth of the cogon grass has occurred, systemic herbicides
(chemicals are carried through the plant tissues to the roots) are applied.
The best time to apply herbicides is in the early
fall before first frost. A 2% solution of glyphosate (e.g., Roundup®)
is recommended in areas that will be immediately revegetated, because glyphosate
has no residual soil activity. In areas where immediate revegetation is not
planned, and non-target plant damage is not a concern, application of a 1-1.5%
solution of imazapyr (e.g., Arsenal®) may be considered. IMPORTANT: Because
imazapyr is highly active in soil, it has a high potential for leaching into
groundwater, so should only be used when groundwater impacts can be eliminated
or minimized. Additionally, nearby trees or other plants may be damaged by
improper application of this herbicide.
Revegetation
may be necessary following herbicide treatment, to prevent soil erosion and
to help reduce reinfestation by cogon grass. For roadside areas, revegetation
with bahia grass and bermuda grass have been used successfully for these
purposes. In natural areas, the choice of which species to use for revegetation
becomes more difficult. For some areas, assisting the process of natural
revegetation succession may be the best choice. Once decisions are made regarding
the ultimate goal of the restoration project, revegetation plans should
be made accordingly. Regardless of the goal, the area should be revegetated
quickly to allow a stable plant community to be established. Lastly, it is
important to exercise diligence, as it will be necessary to scout areas that
have been treated for cogon grass and spot treat new plants with herbicides.
It may not be possible to use all of the methods
prescribed above in every situation, but most effective control will be gained
by using as many of the steps outlined above as possible. In areas
where burning, mowing, or discing, are not possible, spot treatment with
herbicides will help to control cogon grass. Revisit treated areas
frequently and retreat with herbicides as necessary. The best time to begin
a control program is late spring to mid-summer when cogon grass is experiencing
peak growth. Some control measures, such as mowing and spot spraying with
herbicides, can be implemented year round.
Burning has also been used successfully in controlling
cogon grass. As with mowing, burning stimulates the growth and spread of
cogon grass, making followup control a necessity. If you are interested in
attempting this technique, contact management specialists listed below for
more specific information. Also, be sure to obtain all required permits before
attempting a burn even on small infestations.
USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS.
NOTICE: MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.
CONTACTS
For more information on
the management of cogon grass, please contact:
- Donn G. Shilling, Ph.D., University
of Florida, Weed Science / Agronomy, Center Director and Professor, West
Florida Research and Education Center, (850) 484-4482 or 983-2632, dgs at gnv.ifas.ufl.edu
- Eric R. R. L. Johnson, University of Florida,
Graduate Research Assistant, Weed Science / Agronomy, (352) 392-7512,
Voice mail (352) 392-6598 ext 310, errlj at nersp.nerdc.ufl.edu
SUGGESTED ALTERNATIVE PLANTS
A number of
native plants should be considered for replanting areas that were infested with
cogon grass. Along roadsides, bahia grass (Paspalum notatum) is
a possible choice. Each scenario will require a different approach to return
an area previously infested with cogon grass to a healthy ecosystem. Specialists
in cogon grass management should be contacted for assistance.
OTHER LINKS
AUTHORS
Eric R. R. L. Johnson, University of Florida,
Weed Science, Gainesville, FL
Donn G. Shilling, Ph.D., University of Florida,
Weed Science, Milton, FL
EDITOR
Jil M. Swearingen, National Park Service, Washington,
DC
PHOTOGRAPHS
Jeffrey Lotz and Luanne Marsh with
the Florida Dept. of Agriculture, Division of Plant Industry
REFERENCES
Gaffney, J. F. 1996. Ecophysiological and technological
factors influencing the management of cogon grass (Imperata cylindrica). Dissertation.
Agronomy Department, University of Florida, Gainesville, Florida.
Johnson, E. R. R. L. and D. G. Shilling. 1998.
Hernando County Final Report. Agronomy Department, University of Florida,
Gainesville, Florida.
Lippincott, C. L. 1997. Ecological consequences
of Imperata cylindrica (cogon grass): Invasion in Florida Sandhill. Dissertation. Botany
Department, University of Florida, Gainesville, Florida.
Plant Conservation
Alliance, Alien Plant Working Group.
|