Shawn Askew (@vtturfweeds), PhD Associate Professor, Turf Weed Specialist Virginia Tech

Ahh… the nostalgia of the close cropped, well manicured bermudagrass lawn. Having been raised in the South, thoughts of bermudagrass conjure images of pine needles, magnolias, and the sweet smell of Gardenias. I’ve found, however, that the further I migrate north, the more my beloved bermudagrass loses its favor. Images of overgrown flower beds, contaminated fescue lawns, and those hideous patches of brown in an otherwise green fall lawnscape tend to conjure smells other than sweet Gardenia. Even the name tends to change as you approach the Mason-Dixon Line. What once was called “bermudagrass” and had a place among the prominent turfgrasses where PGA golf events and national football games are hosted, is now called “wiregrass” with a lump in one’s throat that is often hard to swallow. Don’t get me wrong, as a research scientists and extension specialist, I know that certain cultivars of bermudagrass have an excellent fit as turfgrass in the transitional climate zone and even further north. It is hard, though, to convince the citizens of the north of positive bermudagrass attributes when all-out war has been waged against the grass for so many years. So I find myself, once again, writing an article with the sole purpose of driving bermudagrass back to the fiery depths of, well, from where it came.

The Problem: Bermudagrass poses such problems in cool-season lawns for two main reasons. It is almost impossible to kill and it is almost impossible to kill. It survives most environments with less water, less nutrient, less fungicide, and less topsoil. About the only thing the grass can’t tolerate is less light and we will get to that in a moment. Bermudagrass is a C4 grass meaning it has a method of metabolism that is more efficient in hot weather than our C3 cool-season grasses. Plants can persist as stolons and rhizomes and common types also may spread by seed. It protects itself from threats by distributing nutrients and other needs over a vast network of conductive tissue, going dormant when needed to avoid extreme stress, and using adventurous stolons to “find new ground” and overcome competing vegetation. Yes, it is a pain and you already know that; let’s get to the part where we kill it.

Cultural Control: Most extension recommendations will have that section on cultural control or nonchemical control, right? It is sort of like the appetizer that you eat while you wait for the “real meal” to be served. But listen to what I tell you. Bermudagrass can’t be controlled without the use of cultural methods. The best way to control bermudagrass is by raising the mowing height of cool-season grasses into the “jungle” range because bermudagrass can’t tolerate low light. Research has shown that tall fescue can completely kill bermudagrass at a mowing height of 4 inches without use of herbicides. Have you ever seen tall fescue that was really mown at 4 inches? It is a bit shaggy and mowers tend to leave tire tracks for a day or so but your fescue will love you for it. Your fescue will be so happy, it will give you darker green color, more drought resistance, more disease resistance, and of course, a barrier against weeds that is to die for – if you are a weed. Another way to know that your fescue loves you at a 4 inch mowing height is that it will continue to reach up and try to hug you. In other words, it grows really fast and must be mown more frequently. Cool-season turfgrass managed at the lower end of recommended mowing heights or less will reduce the effectiveness of herbicide controls for bermudagrass to such an extent that control is nearly impossible. You must maintain cool-season turfgrass at the upper end of recommended mowing heights if you intend to be successful at controlling bermudagrass.

Chemical Control: For those who skipped straight to this section, please see the cultural control section for an important announcement. There are only a few herbicides that will harm bermudagrass more than tall fescue. And by the way, that is about as good as it gets. You can “harm bermudagrass more than you harm fescue”. The goal of your herbicide program is to apply repeated treatments that continue to suppress bermudagrass while allowing the cool-season lawn to expand without causing excessive injury. The following table outlines the tools in the toolbox and how they apply to our typical lawn grasses for selective control.

Bermudagrass Control option table

Note: Trade names are not meant to be exclusive of other suitable products that use the same active ingredient. Read and follow the product label. Rates shown are the maximum single use rate. In some cases, this rate must be reduced depending on the number of times bermudagrass will be treated in the cool-season turf.

Based on research at Virginia Tech and other universities, the following control strategies are currently recommended for bermudagrass in tall fescue lawns:

Option 1, Renovate: Spray patches of bermudagrass in late June or early July with glyphosate (e.g., Roundup™) at 5 quarts of product per acre. Keep the site irrigated to promote regrowth and treat again 3-4 weeks later. One week after the second treatment, either install sod or seed the treated area.

Option 2, Pylex + Turflon: Apply a combination of 1 oz/A Pylex and 32 oz/A Turflon with 0.5 % methylated seed oil adjuvant starting around the middle of August and repeated every 3 weeks for a total of three treatments. The timing of this program is late in the season as we are limited to only three treatments of Pylex per year and, when applied in fall, the Pylex + Turflon program can reduce bermudagrass winter survival. To prevent early summer recovery of any surviving bermudagrass in the next year, apply Tenacity + Turflon (See option 3) in the spring.

Option 3, Tenacity + Turflon: Apply Tenacity at 4 oz/A plus Turflon at 32 oz/A starting in late spring when bermudagrass is about 50% green and growing. Repeat the treatment three to four times at 3-week intervals. This program will reduce bermudagrass expansion during the summer. It is a great program to mix with the Options 2, 4, or 5.

Option 4, Acclaim + Turflon:  Acclaim at 28 oz/A plus Turflon at 32 oz/A can be applied monthly starting when bermudagrass is about 50% green and growing. Fall treatments are more effective than spring and summer treatments. This program can be expensive so a more economical approach is to use Option 3 in spring/summer and follow with monthly applications of Acclaim + Turflon in fall.

Option 5, Ornamec + Turflon:  Apply a combination of Ornamec at 24 oz/A and Turflon at 32 oz/A when bermudagrass is 50% green in spring and repeat the treatment in fall just before bermudagrass enters dormancy. This program may be used in conjunction with other programs.

Other considerations: In addition to the extreme importance of managing tall fescue turf at or near 4 inches mowing height, fall seeding to fill voids left by dying bermudagrass is also important. It is best to seed desirable tall fescue in fall following the treatment programs. Turflon Ester requires a 3-week post-treatment delay before tall fescue can be seeded. It may be necessary to exclude Turflon from the final fall treatment to allow for more immediate seeding of tall fescue when using Pylex. Acclaim and Ornamec also have seeding restrictions so consult the label.

Do's and Don'ts in Bermudagrass Control

Do:

1) Make sure that your lawn is predominately tall fescue as similar turfgrasses may be harmed by some of these programs.

2) Test your soil and make sure the cultural program you are using to manage your tall fescue lawn is optimum, with 3.5 to 4.0 inch mowing heights and fall fertility being the most important.

3) Concentrate more effective herbicides in the fall. If you are only willing to apply a few times, make sure they are in the fall rather than spring or summer.

4) Keep an eye out for conditions that promote tall fescue disease as these herbicide treatments can temporarily injure tall fescue and make it more vulnerable to disease.

5) Read and follow herbicide labels.

Don't:

1) Mow your lawn within 3 days before or after a herbicide treatment.

2) Apply herbicides immediately before a rainfall or irrigation event or during any longterm stressful condition, such as drought, that is limiting the growth rate of the bermudagrass.

3) Exceed herbicide rates or spray herbicides with a sprayer that has not been calibrated to deliver a known rate of spray. With a pump sprayer, we "calibrate ourselves" by simply determining how much water we spray over a known area and use that metric to determine mixing rates.

4) Mow your lawn at less than 3.5 inches tall while trying to kill bermudagrass selectively.

5) Mow your lawn at an interval greater than 7 days when tall fescue is growing optimally.