Removing Perennial Ryegrass and Poa annua in Dormant Zoysiagrass and Bermudagrass

Unwanted guests. We’ve probably all had one at some point in time, but imagine if that same unwanted guest came back year after year. Meet perennial ryegrass and Poa annua, two types of grasses that commonly emerge in dormant zoysiagrass and bermudagrass. These two grasses can be a nuisance to lawn care professionals, but there are ways to keep them from popping up.

Poa annua control

While Poa annua may be defined as a cool season grass, in many cases, it acts like more of a weed. That’s due in part to the fact that it aims to take control of turf, spreading rapidly and resulting in the death of non-mature turfgrass. While poa can be beneficial on golf courses due to its adaptability and resilience to traffic, it establishes fast—not good for lawn care professionals looking to keep it away.

Its adaptability and resilience are a double-edged blade, however, because when poa is introduced to other types of turfgrass, it will compete with them and often win. A poa takeover can spell disaster for turf. To add insult to injury, it often blends in since it looks very similar to Kentucky bluegrass. Remember, unless you already have Kentucky bluegrass, if you see something that looks like it, it’s probably Poa annua.

Tackling Poa annua in bermudagrass and zoysiagrass can be accomplished under full dormancy or in actively growing turf. Using a pre-emergent herbicide in the fall is the first line (and best line) of defense against poa—providing the product several months to seep into the soil and kill it at the source come spring.

Bermudagrass is very tolerant to post-emergent herbicides in almost any growing stage. In areas where full dormancy has been reached, RoundUp or Diquat can be used to achieve control (this is also a great time to get those pre-emergents we mentioned ready).

RoundUp or Diquat can also be used on zoysiagrass in instances where full dormancy has been reached. If used in areas where zoysiagrass hasn’t reached full dormancy (breaking from partial dormancy), zoysiagrass is not as tolerant to post-emergent herbicides as bermudagrass and caution should be used, as this can set back the process of it returning to active growth. If total dormancy is not achieved, it is best to wait for active growth to return in order to avoid injury.

Perennial ryegrass control

Sticking with the cool season theme, perennial ryegrass is often found in the northern United States and, unlike Poa annua, is a useful, tough grass. While perennial ryegrass is a common choice for homeowners and property owners as their turf of choice, it can also pop up where it isn’t wanted.

The presence of perennial ryegrass as overseed is very common in bermudagrass, but is not common in zoysiagrass, since most zoysiagrass is either left dormant or colorants/paints are used to maintain its appearance.

Tackling control of perennial ryegrass in bermudagrass can be done at pretty much any time since it’s very resilient and will generally transition well if overseeded at a lower rate. At a higher rate, it’s prudent to begin control when the bermudagrass is no longer dormant, which will make the transition smoother.

Choosing an herbicide

Now that we’ve explored why Poa annua and perennial ryegrass can cause issues, it’s time to choose an herbicide—and there are plenty, both pre- and post-emergent, to choose from. Each of the following products have their own unique characteristics that make them a good choice for poa and perennial control. For more info, click on each product to check out the label and SDS.

RoundUp QuikPro SC Total Herbicide: A non-selective pre- and post-emergent solution with quick knockdown

Diquat SPC 2L: A non-selective post-emergent that can be used in a tank-mix with pre-emergent

Revolver: Post-emergent specifcally designed for controlling annual and perennial grasses in zoysiagrass and bermudagrass (Residential use permissible if overseeded)

Tribute Total: Provides post-emergent control of weeds in bermudagrass and zoysiagrass

Katana: Selective herbicide that kills Poa annua and perennial ryegrass

Negate 37WG: A post-emergent Sulfonylurea herbicide for control of weeds in bermudagrass and zoysiagrass (NOT for use on residential turf)

Pro tip: Adding a quality surfactant and soluble ammonium sulfate are great ways to increase the efficacy of these products and help you eliminate perennial ryegrass and Poa annua in your turfgrass, too. If you have questions about the products we recommend, are interested in learning more, or are looking for tips/advice, one of our representatives would be happy to chat with you.