I keep seeing posts asking how to control bermudagrass in a turf type tall fescue lawn so I thought I would write a post summarizing the research I have found on this topic. I have a tall fescue lawn and my neighbor has bermudagrass so intrusion over the last 5 years has hit a tipping point. There has been much research at universities that specialize in turfgrass sciences on this topic. The amount of the spread and aggressiveness of the approach dictates your path to control. The best approaches rely on multiple types of herbicides to attack multiple biological systems (see herbicide classes below), because bermudagrass is very resilient and at its peak growing season resistant to even the best selective herbicides. Controlling bermudagrass is a systemic approach of starving it of nutrients through lack of fertilizer and selective herbicide assault. Hopefully you find this useful.
Just for reference, I am in Nashville, TN which is zone 7a in the transition zone so adjust the timing of applications and overseeding according to your area.
Abbreviations used are acre (A), fluid ounce (oz), milliliter (mL), non-ionic surfactant (NIS), methylated seed oil (MSO), crop oil concentrate (COC) and 1000 sq. ft. (M). Small volumes in ounces are best converted to milliliters and measured using a syringe you can get from a pharmacy or buy a box of them on Amazon.
Glyphosate
If the Bermudagrass is contained to a few well-defined areas, then the non-selective herbicide glyphosate can be used. Glyphosate or glyphosate + fluazifop are the most economical options. An article in Turfgrass Trends by the University of Arkansas (https://archive.lib.msu.edu/tic/tgtre/article/2001aug1a.pdf) outlines the treatment plan.
Selective Herbicides & Overseeding
The next 2 options are for larger areas where the Bermudagrass is intermixed with the fescue. Two selective herbicides are available, the less expensive option fluazifop and the more expensive, but more potent and less toxic to fescue option, topramezone. In both instances overseeding (aka. interseeding) significantly aids in successful eradication (https://www.cambridge.org/core/jour...actylon-control-with-topramezone-and-triclopyr/DEC0FAE8150934D42D6EA6E20173A9E0), see below for more discussion on this.
Fluazifop/Fenoxaprop
The University of Tennessee recommends the following regimen for controlling Bermudagrass in fescue using fluazifop (https://extension.tennessee.edu/Sul...-1294e9e2e95b&RootFolder=%2FSullivan%2FDocuments%2FAg%20Documents&CurrentPage=1):
This regimen must be continued for 2-3 years.
See Application Timing below for new data on suggested application timing.
Fenoxaprop can be used as it is less toxic to tall fescue, but it is less effective than Pylex even when combined with overseeding (https://www.cambridge.org/core/jour...actylon-control-with-topramezone-and-triclopyr/DEC0FAE8150934D42D6EA6E20173A9E0).
Topramezone
This herbicide was created to control grassy weeds (i.e. Bermudagrass) in cool season grasses. In correspondence with BASF, their technical team recommends the following application plan:
BASF stated you can move the initial application timeline up to mid-July and proceed from there, but see the Application Timing section below for new data on suggested application timing and why it may not a good idea to move the timing up to July. Any time sooner than mid-July and the Bermudagrass has the ability to grow through the Pylex inhibition.
The program should be administered for 2 years, but substantial suppression should occur in the first year.
Since mesotrione is in the same herbicide class as topramezone, what about adding it to the mix? Virginia Tech has an article on using mesotrione and triclopyr to control Bermudagrass (https://archive.lib.msu.edu/tic/golfd/article/2008mar80.pdf). According to this study fenoxaprop + triclopyr is more effective than mesotione + triclopyr. This added to the fact and that topramezone is more effective than mesotrione, it is probably not worth using mesotrione for this purpose as it would cost more than Pylex. Additionally the rates used in this study exceed the annual maximum application rate for mesotrione.
Even though it is expensive, Pylex is more cost effective than mesotrione or fenoxaprop given its effectiveness and amount used per application. If price is an issue, then fluazifop is the next best approach. Just remember that overseeding is a key factor to success when using either selective herbicide.
Research on Application and Overseeding Timing
Research in 2013 from the University of Tennessee suggests that applications in mid-late April and early September/October seem to have the most effect in suppression (https://www.cambridge.org/core/jour...ssion-with-mixtures-of-fluazifop-and-triclopyr/6117FB8602336EB8FEAF3A84C3392DDB). This study suggests that an application in April when Bermudagrass is first coming out of dormancy impairs its ability to quickly recover in time for its prime growing season and applications in fall, as the temp drops below 72F, inhibit its ability to store energy to survive winter, which really stresses the Bermudagrass. You would just need to be sure to leave enough time in the fall for your overseeding to be established prior to winter.
If you want to geek out you can determine the Growing Degree Days (GDD) for your area like they used in the paper above. GDD is a temperature-based indicator for assessing crop development. It is a calculation used by crop producers that is a measure of heat accumulation used to predict plant and pest development rates such as the date that a crop reaches maturity. Growing degrees (GDs) is defined as the mean daily temperature (average of daily maximum and minimum temperatures) above a certain threshold base temperature accumulated on a daily basis over a period of time. The base threshold temperature is that temperature below which plant growth is zero. For cool season grasses that temperature is 50F or 10C. The Syngenta website (https://www.greencastonline.com/growing-degree-days/home) has a calculator for this (you can look up the equation online if you are interested). You should select 10C as the Base Temperature in order to match that of the paper and the germination temp of cool season grasses. The days that had the most inhibition in that paper were GDD10C of 200 and 2550 with 1775 also being significant.
In the study, GDD10C days fell on 4/22/2009 & 4/28/2010 (200), 8/24/2009 & 8/11/2010 (1775) and 11/5/2009 & 9/9/2010 (2250). Using 2019 data for my area these days roughly fell on 4/21/2019 (200), 8/9/2019 (1775) and 9/24/2019 (2250). For 2020 those dates are 4/11/2020 (200) and the 1775 and 2550 GDD10C have not yet occurred, but my application timing will roughly coincide with these dates.
My Hybrid Approach
I chose to use a hybrid of these approaches to maximally stress the Bermudagrass and minimize its spread during to summer. I applied fluazifop + triclopyr in early May (I did get my chemicals in time for a late April application) and June, did/will not fertilize May-August and will apply Pylex in the fall as well as overseed. UPDATE: I applied Pylex+triclpyr on 8/5.
By late June the Bermudagrass (and other grassy weeds) were completely yellow, but came back in early July. This robbed it of an entire month of growth so hopefully that inhibited its spread over that month. I will not know the success of this approach until late fall and spring of next year.
Herbicide Background
A quick background on the herbicides follows. A good summary chart can be found here (https://weedscience.missouri.edu/publications/2017_Updated_ClassificationPoster.pdf).
Lipid synthesis inhibitors:
Growth regulators:
Amino Acid Synthesis Inhibitor: glyphosate (tradenames: RoundUp, RoundUp Pro)
Pigment inhibitors:
Just for reference, I am in Nashville, TN which is zone 7a in the transition zone so adjust the timing of applications and overseeding according to your area.
Abbreviations used are acre (A), fluid ounce (oz), milliliter (mL), non-ionic surfactant (NIS), methylated seed oil (MSO), crop oil concentrate (COC) and 1000 sq. ft. (M). Small volumes in ounces are best converted to milliliters and measured using a syringe you can get from a pharmacy or buy a box of them on Amazon.
Glyphosate
If the Bermudagrass is contained to a few well-defined areas, then the non-selective herbicide glyphosate can be used. Glyphosate or glyphosate + fluazifop are the most economical options. An article in Turfgrass Trends by the University of Arkansas (https://archive.lib.msu.edu/tic/tgtre/article/2001aug1a.pdf) outlines the treatment plan.
- Apply Roundup Pro (higher concentration glyphosate) at 2 quarts/A (1.5 oz/M) or Roundup Pro + fluazifop at 24 oz/A (0.6 oz/M) to actively growing Bermudagrass.
- The important part is 3 applications, 30-60 days apart (as the Bermudagrass greens up). Any fewer applications is not effective. Spraying brown Bermudagrass is useless as it must be actively growing for these herbicides to work so do not apply the next app until the Bermuda is greening up and regrowing.
- Wait 2 weeks before seeding.
- The following spring spot spray any remaining Bermudagrass.
Selective Herbicides & Overseeding
The next 2 options are for larger areas where the Bermudagrass is intermixed with the fescue. Two selective herbicides are available, the less expensive option fluazifop and the more expensive, but more potent and less toxic to fescue option, topramezone. In both instances overseeding (aka. interseeding) significantly aids in successful eradication (https://www.cambridge.org/core/jour...actylon-control-with-topramezone-and-triclopyr/DEC0FAE8150934D42D6EA6E20173A9E0), see below for more discussion on this.
Fluazifop/Fenoxaprop
The University of Tennessee recommends the following regimen for controlling Bermudagrass in fescue using fluazifop (https://extension.tennessee.edu/Sul...-1294e9e2e95b&RootFolder=%2FSullivan%2FDocuments%2FAg%20Documents&CurrentPage=1):
- Apply Fusilade II at 6 oz/A (0.14 oz/M) + triclopyr at 32 oz/A (0.73 oz/M) + NIS starting when the Bermudagrass is green and actively growing (mid-May). Do not apply fluazifop when the fescue is under stress (i.e. heat, drought).
- Apply every 28 days until August 15th
- Wait 15 days before overseeding or 30 days if bare soil, then overseed.
- Fertilize at 1 lb. N/M in September 15, November 1 and March 1 to support fescue growth. Do not fertilize after April 1 and before September 1 in order to stress the Bermudagrass. This aids in Bermudagrass suppression because it limits the storage of up nutrients prior to summer and in the fall as it tries to store carbohydrates for winter.
This regimen must be continued for 2-3 years.
See Application Timing below for new data on suggested application timing.
Fenoxaprop can be used as it is less toxic to tall fescue, but it is less effective than Pylex even when combined with overseeding (https://www.cambridge.org/core/jour...actylon-control-with-topramezone-and-triclopyr/DEC0FAE8150934D42D6EA6E20173A9E0).
Topramezone
This herbicide was created to control grassy weeds (i.e. Bermudagrass) in cool season grasses. In correspondence with BASF, their technical team recommends the following application plan:
- Mid-August - 1.5 oz/A (0.034 oz or 1.0 mL /M) Pylex + 32 oz/A (0.73 oz or 21.5 mL /M) triclopyr + MSO or COC
- Early-Mid September (21 days from previous app) - 1.5 oz/A (0.034 oz or 1.0 mL /M) Pylex + 32 oz/A (0.73 oz or 21.5 mL /M) triclopyr + MSO or COC
- Early October (21 days from previous app) - 1.0 oz/A (0.023 oz or 0.7 mL /M) Pylex (no triclopyr) + MSO or COC + overseeding. Seeding can occur immediately. According to the article posted above this is a critical step.
BASF stated you can move the initial application timeline up to mid-July and proceed from there, but see the Application Timing section below for new data on suggested application timing and why it may not a good idea to move the timing up to July. Any time sooner than mid-July and the Bermudagrass has the ability to grow through the Pylex inhibition.
The program should be administered for 2 years, but substantial suppression should occur in the first year.
Since mesotrione is in the same herbicide class as topramezone, what about adding it to the mix? Virginia Tech has an article on using mesotrione and triclopyr to control Bermudagrass (https://archive.lib.msu.edu/tic/golfd/article/2008mar80.pdf). According to this study fenoxaprop + triclopyr is more effective than mesotione + triclopyr. This added to the fact and that topramezone is more effective than mesotrione, it is probably not worth using mesotrione for this purpose as it would cost more than Pylex. Additionally the rates used in this study exceed the annual maximum application rate for mesotrione.
Even though it is expensive, Pylex is more cost effective than mesotrione or fenoxaprop given its effectiveness and amount used per application. If price is an issue, then fluazifop is the next best approach. Just remember that overseeding is a key factor to success when using either selective herbicide.
Research on Application and Overseeding Timing
Research in 2013 from the University of Tennessee suggests that applications in mid-late April and early September/October seem to have the most effect in suppression (https://www.cambridge.org/core/jour...ssion-with-mixtures-of-fluazifop-and-triclopyr/6117FB8602336EB8FEAF3A84C3392DDB). This study suggests that an application in April when Bermudagrass is first coming out of dormancy impairs its ability to quickly recover in time for its prime growing season and applications in fall, as the temp drops below 72F, inhibit its ability to store energy to survive winter, which really stresses the Bermudagrass. You would just need to be sure to leave enough time in the fall for your overseeding to be established prior to winter.
If you want to geek out you can determine the Growing Degree Days (GDD) for your area like they used in the paper above. GDD is a temperature-based indicator for assessing crop development. It is a calculation used by crop producers that is a measure of heat accumulation used to predict plant and pest development rates such as the date that a crop reaches maturity. Growing degrees (GDs) is defined as the mean daily temperature (average of daily maximum and minimum temperatures) above a certain threshold base temperature accumulated on a daily basis over a period of time. The base threshold temperature is that temperature below which plant growth is zero. For cool season grasses that temperature is 50F or 10C. The Syngenta website (https://www.greencastonline.com/growing-degree-days/home) has a calculator for this (you can look up the equation online if you are interested). You should select 10C as the Base Temperature in order to match that of the paper and the germination temp of cool season grasses. The days that had the most inhibition in that paper were GDD10C of 200 and 2550 with 1775 also being significant.
In the study, GDD10C days fell on 4/22/2009 & 4/28/2010 (200), 8/24/2009 & 8/11/2010 (1775) and 11/5/2009 & 9/9/2010 (2250). Using 2019 data for my area these days roughly fell on 4/21/2019 (200), 8/9/2019 (1775) and 9/24/2019 (2250). For 2020 those dates are 4/11/2020 (200) and the 1775 and 2550 GDD10C have not yet occurred, but my application timing will roughly coincide with these dates.
My Hybrid Approach
I chose to use a hybrid of these approaches to maximally stress the Bermudagrass and minimize its spread during to summer. I applied fluazifop + triclopyr in early May (I did get my chemicals in time for a late April application) and June, did/will not fertilize May-August and will apply Pylex in the fall as well as overseed. UPDATE: I applied Pylex+triclpyr on 8/5.
By late June the Bermudagrass (and other grassy weeds) were completely yellow, but came back in early July. This robbed it of an entire month of growth so hopefully that inhibited its spread over that month. I will not know the success of this approach until late fall and spring of next year.
Herbicide Background
A quick background on the herbicides follows. A good summary chart can be found here (https://weedscience.missouri.edu/publications/2017_Updated_ClassificationPoster.pdf).
Lipid synthesis inhibitors:
- fluazifop (tradenames: Ornamec Over the Top, Fusilade II)
- fenoxaprop (tradename: Acclaim Extra)
Growth regulators:
- triclopyr (tradenames: Turflon Ester, Triclopyr 4)
- As an aside, most 3-way herbicides (2,4-D, MCPA, dicamba) and quinclorac are in this class. Sulfentrazone and carfentrazone are not and are cell membrane disruptors.
Amino Acid Synthesis Inhibitor: glyphosate (tradenames: RoundUp, RoundUp Pro)
Pigment inhibitors:
- mesotrione (tradenames: Tenacity, Meso 4SC)
- topramezone (tradename: Pylex)
