Without question, Cogongrass is the most troublesome invasive plant that I (and my clients) deal with. Here in Northwest Florida, we have a lot of it, and it is very difficult to manage. With that in mind, I write about cogongrass control with some frequency. If you follow Panhandle Ag e-Newsand/or Panhandle Outdoors you’ve probably seen much of what’s included below before. That’s ok, a refresher never hurt anyone and, unfortunately, there are plenty of folks out there who are just realizing that they have a cogongrass problem.
It has been my observation that the difficulty of management and the corresponding limited early success often led to frustration and ultimately a loss of interest in control efforts on the part of landowners/managers. This is the absolute worst-case scenario, as diligence over time is paramount to successfully managing cogongrass. With all this in mind, optimizing the impact of the initial control effort is crucial both in terms of biology (efficacy on the plants) and psychology (keeping the landowner encouraged and motivated). If you have cogongrass to fight, take every step you can to get the absolute best results out of every treatment, especially the first one.
Cogongrass has no visible jointing, segmentation, or branching above ground. However, in the top 3-6 of the soil it forms a dense mat of white, fleshy, clearly segmented rhizomes which are a key identifying feature. Photo Credit: Mark Mauldin
The following is a discussion of some of the steps you can take to maximize the efficacy of your control efforts.
1) Timing Matters
Cogongrass is best treated with a fall-spring, one-two punch. Mid-summer and mid-winter treatments are not advisable. Based on my experience, the ideal time to treat cogongrass is October through November, before first frost, with good soil moisture. Spray now, during the fall window, and be prepared to spray again in the spring when you have at least 12 inches of green leaf and good soil moisture. I have mentioned “good soil moisture” twice… what exactly does that mean? It means there is sufficient moisture in the soil that the cogongrass is not experiencing any level of drought stress. Herbicide applications made to stressed plant are generally less effective than are applications to made to “happy plants”. It is very hard to see symptoms of drought stress in cogongrass. Generally, you need to look at the plants around the infestation for clues. If any of the plants in the surrounding landscape look wilted or crispy during the heat of the day, it’s probably best to delay herbicide applications. This concept is worth noting primarily because here in the central panhandle we tend to be dry during both the fall and spring application windows. I am writing this article on 10/9/24. At my house we’ve not had a drop of rain since Hurricane Helene came through on 9/27 and my trusty weather app say not to expect any for the next 10 days. While it will vary greatly by location and soil type, it loos to me like we are running out of hurricane moisture, and it is rapidly becoming too dry to spray. All this boils down to the fact that you need to be ready take advantage of the situation and spray when soil moisture is adequate.
With that one-two punch successfully delivered, you should see significant reduction in the size of the infestation by this time next year. Keep repeating the fall-spring process until you can no longer find any cogongrass. Be sure to look carefully, as the infestation retreats it can be easy to miss the less robust and more scattered remnants mixed in with other vegetation. These remnants need to be sprayed, if not rapid regrowth will occur.
Close examination of this cogongrass patch shows regrowth occurring in the patch and growth that was apparently missed by the prior herbicide application. Both of these scenarios are common and help to illustrate why it is important to scout diligently and be prepared for re-treatments. Photo credit: Mark Mauldin
2) Coverage & Leaf Area are Crucial
To make the most out of each treatment you must maximize the amount of chemical you get into the plant. This is done by getting thorough coverage on as much green leaf area as possible. Make sure you have plenty of green leaves (at least 12inches) and spray them like you’re painting a wall. You don’t want runoff, but you want every square inch of leaf covered with spray. Don’t mow or burn for at least 30 days after you spray. Cogongrass can be hard to spot when it is growing mixed with other grasses/green foliage. Look diligently to find the edge of the patch and then spray 10ft past the known edge on all sides of the patch.
3) Get the Spray Mixture Right
Notice, I didn’t say pick the right chemical. There’s more to it than that. The following recommendations will be based on managing cogongrass with the active ingredient glyphosate. (Imazapyr is also very effective on cogongrass, but due to its soil activity it is inherently more complicated to use and ensure the safety of desirable plants near the treatment area. I am not comfortable recommending imazapyr without first seeing the site where it is to be applied and discussing the risk to other vegetation with the landowner. Glyphosate must enter a plant through a green leaf making it much easier for applicators to ensure the safety of desirable vegetation.)
Generally speaking, the efficacy of glyphosate will increase if a water conditioner and surfactant are included in the spray solution. To clarify, this means there would be three separate products going into the spray tank – one herbicide and two adjuvants. The preferred water conditioner would be a 34% liquid Ammonium Sulfate (AMS) product and the surfactant would be an 80/20 Non-ionic surfactant (NIS). These products should be available anywhere ag chemicals are sold (not the garden center at a big box store) under many different name brands. Selecting a glyphosate product can be somewhat confusing, simply because there are so many different products on the market. The product amounts listed below are based on a 41%, 3lbs acid equivalent (ae) per gallon glyphosate product. This is a relatively common formulation, but there are many others available. All can be effective; it is just a matter of value and correctly adjusting the rate to match the formulation you are using.
For a broadcast application using a tractor mounted sprayer or other similar equipment, mix a spray solution such that 1 gallon of 41%, 3lbae glyphosate herbicide is applied per acre. Ideally this would be delivered in 10-20 gallons of water (be sure spray equipment is properly calibrated). Add a liquid AMS water conditioning product at 2% v/v before adding herbicide to the tank. Add a non-ionic surfactant (80/20 NIS) at 1qt per 50-100 gallons of spray solution after the herbicide has been added.
I understand that nobody likes to have to deal with all the numbers, especially the various formulations of glyphosate. Unfortunately, that’s just part of it… There are so many different products out there that the numbers are necessary to communicate the recommendations in a way that is widely applicable. Please don’t hesitate to contact me (850-638-6180) or your local UF/IFAS Extension Agent for assistance sourcing vegetation management products or tailoring the recommendations to match the specific products you have on hand. The most important thing is to get the mixture right and make the application be as effective as possible.
More than any other weed I manage, Cogongrass penalizes the applicator for not paying attention to the details. It is a very difficult plant to control; partial efforts are essentially a waste of time. I encourage you to take the extra time, effort, and expense and make the most of every application.
Cogongrass (Imperata cylindrica) is one of the most noxious weeds in the U.S. and has been a problem in the agricultural and timberland for decades. In more recent years it has been found on our barrier islands. Stands of cogongrass on the beaches are not as massive and dense as they are in the upland regions of our district, but now is the time to try and manage it before it does. And NOW is the time to identify whether you have it on your property or not – it is in seed.
Cogongrass shown here with seedheads – more typically seen in the spring. If you suspect you have cogongrass in or around your food plots please consult your UF/IFAS Extension Agent how control options. Photo credit: Mark Mauldin
Cogongrass produces blades that resemble St. Augustine but are taller and wider. The blades can reach a height of three feet and the color is more of a yellow green (lime green) than the deep green of St. Augustine. If you can touch the blade, you will notice that the midline of the parallel leaf veins is off center slightly and the edges of the blades are serrated – feeling like a saw blade when you run fingers from top to bottom. They usually form dense stands – with a clumping appearance and, as mentioned, it is currently in seed, and this is very helpful with identification.
The midline vein of cogongrass is off-center. Photo: UF IFAS
The seeds are white, fluffy and elongated extending above the plant so the wind can catch them – similar to dandelions. These can easily be seen from the highway or riding your bike through the neighborhoods. As mentioned above, if you see seeds like this you can confirm the identification by examining the leaf blades. You can also send photos to your county extension office.
The white tufted seeds of cogongrass. Photo: University of Georgia
If the identification is confirmed the next step is to report the location on EDDMapS – https://www.eddmaps.org. You can also do this with the free app IveGotOne (which can be found on the EDDMapS website or any app store). HOWEVER, you cannot report private property without their permission.
The next step would be management. It is not recommended to mow or disturb the plant while in seed. Herbicide treatment is most effective in the fall. Many will mow the plant, allow the grass to resprout no more than 12 inches, and treat this with an herbicide. It is recommended that you contact your county extension office for recommendations as to which herbicide to use and how.
The negative impacts of this noxious grass have been an issue in the upland communities for decades. There have been few major issues with it in the coastal zone, but early detection rapid response is the most effective management plan to keep negative impacts from occurring. We encourage coastal communities to survey for cogongrass while it is in seed and develop a management plan for the fall.
ARE YOU AWARE THAT THE INVASIVE COGONGRASS HAS MADE ITS WAY TO OUR COASTAL AREA?
Many may be familiar with this noxious weed but that is because it has been a problem in agricultural and timber lands for many decades now.
Cogongrass seedheads are easily spotted in spring.
Photo credit: Mark Mauldin
This grass (Imperata cylindrica) is native to Southeast Asia and arrived by accident within cargo delivered to the port of Mobile in the early part of the 20th century. It quickly spread and has been a menace ever since. It can be found in ditches, roadsides, empty lots, golf courses, pastures, and timberlands. On a recent drive south through Mobile County there was nowhere the plant could not be found. The current records on EDDMapS shows the plant has spread through nine states in the southeastern U.S. and every county in Florida. Cogongrass has serrated edges and is imbedded with silica, so is not a popular forage plant with many forms of livestock and wildlife. It burns very hot and has made land management with prescribe fire difficult. States across the south spend hundreds of thousands of dollars annually trying to control the plant. Though working primarily in Santa Rosa and Okaloosa counties of the Florida panhandle, the Longleaf Alliance has a team focused on managing it.
My role with UF IFAS Extension is with Florida Sea Grant, I focus on coastal issues. A couple of years ago, we received a call from a condo manager on Perdido Key who believed they had found cogongrass growing on their property. I, along with natural resource personnel from Escambia County, made a site visit and sure enough – there was cogongrass growing around their swimming pool. It most likely got there by the lawn maintenance crew. This is a common method of spreading this plant. Crews mow the grass down, do not clean their equipment, load it on a trailer, and spread the plant to other locations. However it got there, this was a classic EDRR situation on our islands and plans were made to remove the plant without harming the native sea oats nearby.
Cogongrass, like beach vitex, is allelopathic – it can draw moisture away from nearby plants, killing them, and taking over their space. The plant can grow into thick monocultures displacing the native dune plants and altering the ecology – possibly impacting the federal protected Perdido Key beach mouse. It is a relatively new issue on our barrier islands. The current EDDMapS records show the plant has been found on Horn Island and Petiti Bois Island in Mississippi – Dauphin Island, Ft. Morgan peninsula, and Gulf Shores in Alabama – Perdido Key, Santa Rosa Island, Destin, south Walton, St. Andrew’s State Park, Tyndall AFB, Cape San Blas, St. Vincent Island, Apalachicola, and the St. Marks Wildlife Refuge in the Florida panhandle. This is most likely under reported and notes that the invasion of the coastal areas has begun. A rapid response is needed.
IF I LIVE IN A COASTAL AREA, HOW WOULD I KNOW IF THERE IS COGONGRASS PRESENT?
First it is a grass. It resembles typical turf grass, but the blades are tall – up to three feet high – and the blades are between 0.5-1.0 inches wide. It has a lighter green color than most of the native plants but does become brown in colder weather. It is usually found in very dense patches and looks “invasive” – like it is taking over the landscape. Close inspection of the blades you will find the edges rough (serrated) and the “veins” all running parallel (not branching) with the darker midline not in the middle of the blade but offset to one side. When the grass goes to seed in the spring it can be identified by the white “fluffy” seeds that extend above the grass and are dispersed by the wind – much like dandelions.
The midline vein of cogongrass is off-center.
Photo: UF IFAS The white tufted seeds of cogongrass.
Photo: University of Georgia
Managing this plant is very difficult. Fragments of the rhizomes can generate re-growth and removing all of the rhizomes by hand is very difficult. Herbicide treatment is the most effective and the grass tends to return even with this. The best time to apply herbicide is in the fall.
If you think you may have this grass, contact your county extension office to verify and for advice on how to manage.
Without question, Cogongrass is the most troublesome invasive plant that I (and my clients) deal with. Here in Northwest Florida, we have a lot of it, and it is very difficult to manage. It has been my observation that the difficulty of management and limited early success often lead to frustration and ultimately a loss of interest in control efforts on the part of landowners/managers. This is the absolute worst-case scenario, as diligence over time is paramount to successfully managing cogongrass. With all this in mind, optimizing the impact of the initial control effort is crucial both in terms of biology (efficacy on the plants) and psychology (keeping the landowner encouraged and motivated). If you have cogongrass to fight, take every step you can to get the absolute best results you can, out of every treatment, especially the first one.
Cogongrass is highly invasive, difficult to control and widespread in Northwest Florida.
Phot Credit: Mark Mauldin
The following is a discussion of some of the steps you can take to maximize the efficacy of your control efforts.
1) Timing Matters
Cogongrass is best treated with a fall-spring, one-two punch. Mid-summer and mid-winter treatments are not advisable. NOW is the time to treat. As I write this it is mid-October with rain on the way – by the time this is published the front will have passed and the timing will be perfect. If you ask me the absolute best time of year to treat cogongrass, I will tell you, without hesitation, “October through November, before first frost, with good soil moisture”. Spray now and be prepared to spray again in the spring when you have at least 12 inches of green leaf and good soil moisture. With that one-two successfully delivered you should see significant reduction in the size of the infestation by this time next year. Keep repeating the spring-fall process until you can no longer find any cogongrass.
Getting good herbicide coverage over all of the characteristically lime green foliage of cogongrass is essential for good control.
Photo Credit: Mark Mauldin
2) Coverage & Leaf Area are Crucial
To make the most out of each treatment you must maximize the amount of chemical you get into the plant. This is done by getting thorough coverage on as much green leaf area as possible. Make sure you have plenty of green leaves (at least 12inches) and spray them like you’re painting a wall. You don’t want runoff, but you want every square inch of leaf covered with spray. Don’t mow or burn for at least 30 days after you spray. Cogongrass can be hard to spot, especially if it is growing mixed with other grasses/green foliage. Look diligently to find the edge of the patch and then spray 10ft past the known edge on all sides of the patch.
3) Get the Spray Mixture Right
Notice, I didn’t say pick the right chemical. There’s more to it than that. The following recommendations will be based on using the active ingredient glyphosate. (Imazapyr is also very effective on cogongrass, but due to its soil activity it is inherently more complicated to use and ensure the safety of desirable plants near the treatment area. I am not comfortable recommending imazapyr without first seeing the site where it is to be applied and discussing the risk to other vegetation with the landowner. Glyphosate must enter a plant through a green leaf making it much easier for applicators to ensure the safety of desirable vegetation.)
Generally speaking, the efficacy of glyphosate will increase if a water conditioner and surfactant are included in the spray solution. To clarify, this would be 3 separate products going into the spray tank – one herbicide and two adjuvants. The preferred water conditioner would be a 34% liquid Ammonium Sulfate (AMS) product and the surfactant would be an 80/20 Non-ionic surfactant (NIS). These products should be available anywhere ag chemicals are sold (not the garden center at a big box store) under many different name brands. Selecting a glyphosate product can be somewhat confusing, simply because there are so many different products on the market. The product amounts listed below are based on a 41%, 3lbs acid equivalent (ae) per gallon glyphosate product. This is a relatively common formulation, but there are many others available. All can be effective; it is just a matter of value and correctly adjusting the rate to match the formulation you are using.
An example mixture for treating a small patch with a hand-held single nozzle sprayer:
Fill spray tank ½ – ¾ full of water (run agitation if available)
For each gallon of spray solution you are making add:
3.2oz of 34% AMS water conditioner (add this first and let it completely mix before proceeding)
5oz of 41% 3lbs ae glyphosate herbicide
0.5oz of 80/20 NIS
Finish filling spray tank
For a broadcast application using a tractor mounted sprayer or other similar equipment, mix a spray solution such that 1 gallon of 41%, 3lbae glyphosate herbicide is applied per acre. Ideally this would be delivered in 10-20 gallons of water (be sure spray equipment is properly calibrated). Add a liquid AMS water conditioning product at 2% v/v before adding herbicide to the tank. Add a non-ionic surfactant (80/20 NIS) at 1qt per 50-100 gallons of spray solution after the herbicide has been added.
I understand that nobody likes to have to deal with all the numbers, especially the various formulations of glyphosate. Unfortunately, that’s just part of it… There are so many different products out there that the numbers are necessary to communicate the recommendations in a way that is widely applicable. Please don’t hesitate to contact me or your local UF/IFAS Extension Agent for assistance sourcing vegetation management products or tailoring the recommendations to match the specific products you have on hand. The most important thing is to get the mixture right and make the application be as effective as possible.
Miami is ground zero for invasive species in this state. But the Florida panhandle is no stranger to them. Where they are dealing with Burmese pythons, melaleuca, and who knows how many different species of lizards – we deal with Chinese tallow, Japanese climbing fern, and lionfish. The state spends hundreds of thousands of dollars each year battling and managing these non-native problem species. By definition, invasive species cause environmental and/or economic problems, and those problems will only get worse if we do not spend the money to manage them. Those who work in invasive science and resource management know that the most effective way to manage these species is to detect them early and respond rapidly.
The Invasive Species Curve
Invasive species have made their way to the coastal waters and dunes of the barrier islands in the Florida panhandle. Beach vitex, Brown anoles, and Chinese tallow are found on most. Recently on Perdido Key near Pensacola, we found a new one – cogongrass.
Cogongrass (Imperata cylindrica) was accidentally introduced to the Gulf coast via crates of satsumas entering the port of Mobile in 1912. It began to spread from there and has covered much of the upland areas of the southeastern U.S. It has created large problems within pasture lands, where livestock will not graze on it, and in pine forest where it has decreased plant and animal biodiversity as well as made prescribed burning a problem – it burns hot, hot enough to actually kill the trees. The impacts and management of this plant in that part of the panhandle has been known for a long time. The Department of Agriculture lists it as one of the most invasive and noxious weeds in the country.
Cogongrass seedheads are easily spotted in spring.
Photo credit: Mark Mauldin
Two years ago cogongrass was discovered growing around a swimming pool area at a condo on Perdido Key. To be considered an invasive species you must (a) be non-native to the area – cogongrass is certainly non-native to our barrier islands, (b) have been introduced by humans (accidentally or intentionally) – strike two, we THINK it was introduced by mowers. This is a common method of spreading cogongrass, mowing an area where it exists, then moving those mowers to new locations without cleaning the equipment. We do not know this is how it got to the island, but the probability is high. Third, it has to be causing an environmental and/or economic problem. It certainly is north of the I-10, but it is not known what issue it may cause on our barrier islands. Could it negatively impact protected beach mice and nesting sea turtle habitat? Could alter the integrity of dunes to reduce their ability to hold sand and protect properties. Could it overtake dune plants lowering both plant and animal diversity thus altering the ecology of the barrier island itself? We do not know. What we do know is that if we want to eradicate it, we need to detect it early and respond rapidly.
According to EDDMapS.org – there are 75 records of cogongrass on the barrier islands, and coastal beaches of the Florida panhandle. This is most likely under reported. So, step one would be to conduct surveys along your islands and beaches. Florida Sea Grant and Escambia County of Marine Resources are doing just that. EDDMaps reports five records on Perdido Key and four at Ft. Pickens. It most likely there is more. A survey of the northeast area of Pensacola Beach (from Casino Beach east and north of Via De Luna Drive) has found two verified records and two unverified (they are on private property, and we cannot approach to verify). Surveys of both islands continue.
The best time to remove/treat cogongrass is in the fall. The key to controlling this plant is destroying the extensive rhizome system. In the upland regions, simple disking has been shown to be effective if you dig during the dry season, when the rhizomes can dry out, and if you disk deep enough to get all of the rhizomes. Though the rhizomes can be found as deep as four feet, most are within six inches and at least a six-inch disking is recommended. Depending on the property, this may not be an option on our barrier islands. But if you have a small patch in your yard, you might be able to dig much of it up.
Chemical treatments have had some success. Prometon (Pramitol), tebuthurion (Spike), and imazapyr have all had some success along roadsides and in ditches north of I-10. However, the strength of these chemicals will impede new growth, or plantings of new plants, for up to six months. There are plants that are protected on our islands and on Perdido Key any altering of beach mouse habitat is illegal. We certainly do not want to kill plants that are holding our dunes. If you feel chemical treatment may be needed for your property, contact the county extension office for advice.
Most recommend a mixture of burning, disking, and chemical treatment. But again, this is not realistic for barrier islands. Any mechanical removal should be conducted in the summer to remove thatch and all older and dead cogongrass. As new shoots emerge in late summer and early fall herbicides can then be used to kill the young plants. Studies and practice have found complete eradication is difficult. It is also recommended not to attempt any management while in seed (in spring). Tractors, mowers, etc. can collect the seeds and, when the mowers are moved to new locations, spread the problem. If all mowing/disking equipment can be cleaned after treatment – this is highly recommended.
Step one would be to determine if you have cogongrass on your property, then seek advice on how to best manage it. For more information on this species, contact your local extension office.
