August is Cogongrass treatment time

Jul 3, 2024

If you have cogongrass on your property, now is the time to start treating it with herbicide. This perennial grass first introduced in the U.S. in 1912 from the tropical and subtropical regions of the world but has exploded in recent years as an aggressive, invasive species. Early detection and multiple treatments are keys to eradicating cogongrass.

Cogongrass should be fairly easy to identify. When it is actively growing it tends to be bright green and often presents as  a dense patch of grass that outcompetes other vegetation. Cogongrass spreads by rhizome with leaves that are bunched at the soil level, without any branching blades above the ground.

An easy indicator is an off-center whitish mid-rib on each grass blade, which comes to a sharp point. The rhizomes form thick mats under the soil and produce biochemicals that inhibit the growth of other plants, which is why we typically see very little other vegetation within a cogongrass infestation.

Cogongrass if often seen growing along road shoulders and many properties have populations that spread from there. In Georgia, the Georgia Forestry Commission will map, treat, and monitor the site if the landowner contacts their regional Forest Health specialist. In Leon County, Florida, there is a county branch dedicated to the treatment of the right of ways. Contact their office for assistance with a right-of-way infestation.

If you have cogongrass that spread onto your property from the road shoulder, you can coordinate spraying by contacting the county and requesting treatment of the road shoulder simultaneously.

Cogongrass also gets introduced by contracted work, hitchhiking on heavy equipment such as timber harvested equipment. It is important that any heavy equipment you have coming onto your property is properly cleaned before you allow access. Typically, if cogongrass is introduced it often appears first in disturbed soil and logging decks. Disturbing these areas will spread the rhizomes and create new populations of the plant.

The Red Hills Region has been fortunate to not be overrun with this species, but action must be taken quickly to prevent this from becoming the dominant grass in the region, as it has in many other parts of the South and in other countries.

Cogongrass is present throughout the Southeast and there are a number of ways to go about treating it. We compiled a few recommendations from Tall Timbers biologists that have proven regionally successful in its control.

Red Hills region: Kim Sash, Tall Timbers Biological Monitoring Coordinator

We recommend treating the affected area and a buffer around the cogongrass, which varies with the size of the patch, with 24 to 30 ounces Arsenal (Imazapyr) + 2 quarts Glyphosate + 1 quart of Methylated seed oil + 50 gallons water/acre.

The effects from spraying Arsenal take many months to appear. Therefore, we find it helpful to add 2 quarts of Glyphosate to the mix, which will brown the cogongrass but not kill it, allowing you to see any areas you missed when applying your herbicide mix.

The soil activity can target new rhizome shoots growing. Caution, Arsenal is soil active and can cause significant damage or mortality if sprayed under hardwoods, especially oaks, and longleaf if sprayed on the needles, even at low rates.

Treat the patches with glyphosate beginning in the spring using the method above if you are spraying under trees.

Greater Southeast region: Ryan Mitchell, Tall Timbers’ Southeast Private Lands Prescribed Fire Outreach Coordinator

Monitor for new patches after a prescribed burn (typically they recover and green up much quicker than native vegetation), after mowing, any mechanical disturbance, or forestry operation.

In the spring, treat patches with a 4% to 6% glyphosate mix 0.5% nonionic surfactant or Methylated seed oil. Spray 10 feet outside the noticeable patch, to ensure you treat all of the cogongrass. A follow-up treatment with glyphosate in the fall, about a month before growing season is a must.

Using this regimen, Auburn achieved 97% control within three years.

Central Florida: Geoff Bean Research/Prog. Manager, Central FL Rangeland Quail Program (CFRQP)

At our Central Florida Rangeland Quail Program, biologists and land managers have had success in curbing cogongrass using the following treatment.

Spray 4% Roundup Power Max with 1% ammonium sulfate as a surfactant, adding a dye to ensure good coverage on the spray. Spray beyond the cogongrass patch also to make sure get coverage of any new sprouts that are emerging that are difficult to see.

In the areas where the infestation was the worst, biologists then burned the area about a month after spraying and resprayed again when the cogongrass was about 8 inches tall. Repeat the process on any areas that return and spot spray any areas that reappear; one treatment may not be enough. The herbicide mixture useful in areas that are sensitive to imazapyr.

Over the past 100-plus years cogongrass in the U.S. continues to be a problem. It claims the title of the “Top 10 Worst Weeds in the World.” Persistent spraying over multiple years is the best way to keep this longtime invasive species from taking over your property.

For more information about Cogon grass, see the links below.

In Florida: https://edis.ifas.ufl.edu/publication/WG202

In Georgia: https://gatrees.org/cogongrass-in-georgia/

 

 

 

 

 

 

 

 

 

 

About the Author
Tall Timbers
Welcome to our collection of articles that were either a group effort by several staff members or were authored by former staff members. In some cases, additional author information is included in the article. Enjoy!
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