Cogongrass Wars: Extension Experts Marshal Efforts to Fight “Weed From Hell”

Auburn, January 8, 2003 --- It’s been called the weed from hell.  And while experts are 
the first to admit it isn’t possible to send the weed back from where it fictitiously sprang, they are 
looking for ways to contain its rapid spread throughout Alabama’s Gulf Coast region.
Since its accidental introduction into the state almost a half century ago, cogongrass -- 
which, contrary to popular opinion, actually comes from Asia rather than the infernal regions -- 
has caused nothing but trouble for people living and working in the Gulf Coast region.
“This is especially true in the forestry industry, where it’s infested many pine plantings,” 
says Dr. Mike Patterson, an Alabama Cooperative Extension System weed scientist and Auburn 
University professor of agronomy who is helping develop strategies to control the weed’s spread.
	Before foresters can even think about planting a new crop of pine seedlings, they spend 
as much as $200 dollars an acre to beat back cogongrass.  Otherwise, young seedlings, 
particularly longleaf seedlings, will not grow into healthy pines.
	A 6-acre forestry research site was established in Theodore, Ala., to develop more cost-
effective strategies for managing cogongrass, with assistance provided by local industry.  Wilson 
Faircloth, one of Patterson’s agronomy doctoral students, and Dr. Jim Miller, a weed ecologist 
with the USDA’s Southern Forestry Laboratory, spearheaded this effort.	
	Currently, foresters have only two chemicals to control cogongrass – glyphosate, typically 
sold as Roundup and other trade names, and imazapyr, sold as Arsenal, Chopper and other 
product names. 
	But here’s the rub: the chemicals typically have to be applied before the seedlings are 
planted, which means that, with only one exception, there is very little foresters can do later on if 
the grass begins overtaking the seedlings.
	“Neither loblolly nor longleaf seedlings can withstand glyphosate sprayings after 
planting,” Patterson says, “And while loblolly seedlings can tolerate Arsenal applications, longleaf 
seedlings can’t.”
	That leaves Patterson and other researchers with the challenge of finding other methods 
for containing the grass’ spread as the seedlings begin taking root.
	One promising approach under study involves mechanical site preparation prior to 
planting.  
	“After herbicide spraying, we used a fire plow, which throws the cogongrass over to the 
side and creates a 3-foot trench in which the seedlings can be planted,” Patterson says.  
	This removes much of the weed’s biomass, thereby reducing its ability to take root again.
	Another site preparation method involves spraying cogongrass with herbicides in the fall 
while the weeds are still green, followed by pine planting in the winter. 
	“Some experts believe fall treatment is most effective in the way it depletes the weed’s 
carbohydrate food sources it uses for growth the following spring.”
	Initial results show both approaches -- mechanical site preparation and fall spraying – 
can provide foresters with some financial relief.  Mechanical site preparation costs about $100 an 
acre, while fall chemical applications typically run about $75 -- both substantially less than the 
$200 an acre foresters are currently spending to control cogongrass.
	Foresters are not the only people contending with this troublesome weed.  Cogongrass 
also is a bane for state and county highway departments, especially the latter, many of whom 
lack funds to deal with the weeds effectively.  Unfortunately tillage isn’t an option because of the 
risk of roadside erosion.
	With funding provided by the Alabama Department of Transportation, Faircloth and 
Patterson are exploring the interaction between mowing frequency and herbicide application.  
	 “Along with mowing, we’re trying to beat back cogongrass with one or two chemical 
applications,” Patterson says.  “That doesn’t eliminate it entirely, but, hopefully, it will hurt the 
weed enough to shift the competition in favor of more desirable grasses, such as bermudagrass 
and bahia that we plant after spraying.”
	Efforts are also under way to study how cogongrass has managed to establish itself so 
quickly throughout the Gulf Coast region.
	“We know it spreads through the soil thanks to its very active rootstocks,” Patterson says.  
	“But what we really need to understand is its seed dispersal.  We know the seeds can be 
dispersed by wind, but what we don’t know is how much of this seed is viable and actually takes 
root.”
	Two Auburn University researchers -- agronomist Dr. Edzard van Santen and Dr. Ludovic 
Capo-chichi, a geneticist doing post-doctoral work -- are trying to answer this question.  They’ve 
collected cogongrass seeds as far north as Tuscaloosa County to determine the cogongrass 
biotypes that produce viable seed. 
	“Hopefully, these cooperative research efforts will lead to effective management 
strategies for cogongrass in forests and along highway rights-of-way.”
	Indeed, Patterson believes a comprehensive effort will be required by private landowners, 
industries and government agencies to combat cogongrass effectively throughout the state -- an 
effort that will require a “central coordinating group composed of representatives of the major 
stakeholders affected by cogongrass infestations.”
(Source: Dr. Mike Patterson, Extension Weed Scientist, 334-844-5492.)