Oh the weeds. You will never hear me complain about rain (except on gamedays), but these awesome growing conditions are really getting the weeds moving. I am constantly trying to find the right herbicide to apply to treat the unwanted weed growth in my lawn. Out of the four standard warm season turf grasses we have in our area, zoysia, St. Augustine, centipede and bermuda, trying to find the right herbicide to clash with these weeds can be challenging.
The biggest battle lately is with grassy type weeds. Grassy weeds, like all weeds, are divided into perennials and annuals.
PERENNIAL GRASSY WEEDS get established and stay with us year after year. They take up residence and don’t want to leave. Squatters. The most common grasses of our extended stay weeds are nutsedges, bahia, dallisgrass and wild garlic/onion.
Depending on the turf type, these perennials are hard to fight. UGA makes recommendations for how homeowners can fight these pests and I do my own tests as well. Here is what I have found works best for homeowner to control grassy weeds in our turf grasses (with the standard caveat … always read the label on the pesticides you are going to apply. It will save you time, money and the environment.)
Sedgehammer (Halosulfuron) is the best product out there for nutsedges, but that is about all it treats. Image for Nutsedge (Imazaquin) is also a good general product for fighting nutsedges, but it also works great on wild garlic, decent on annual poa annua and sandbur and has some good control on a few common broadleaf weeds as well.
When reading the label on Imazaquin, you can find some pretty cool other herbicide uses for weed control as well. One use is being able to overhead spray certain Junipers, Liriope, Indian Hawthorne, mondograss, Asiatic Jasmine and a host of other ornamentals for various weed control. As a precaution, Image has two available herbicides with the other having atrazine, so when purchasing make sure you are buying the correct Image product.
Martin’s TopShot (metsulfuron) is an underrated product that can be a little harder to find. This is about the best homeowner product available for controlling bahiagrass. And like Image with Imazaquin, TopShot controls a bunch of other weeds as well. All three of these products are labeled to spray on all four of our warm season turf grasses.
ANNUAL WEEDS come from seeds that blow in from the wind, are brought in from birds, or are hand delivered from a lawnmower used to cut a neighbor’s weedy yard.
Crabgrass is our predominant annual warm season weed grass. Poa annua is our most prolific cool season weedy grass. Once these weeds are up, the challenge begins. For instance, the chemical quinclorac will kill crabgrass graveyard dead only in zoysia and bermuda. In St. Augustine and centipede grass, quinclorac is lethal to your expensive turf. But quinclorac doesn’t treat for poa annua. Atrazine will destroy some poa annua, but isn’t labeled for actively growing bermuda. Sethoxydim is fantastic for crabgrass and sandbur, but only in centipede. You see the dilemma. The best control for annual weeds is always going to be a preemergence herbicide.
As seeds lay dormant, they wait just until the temperature is right and pop open. Crabgrass starts opening when the forsythia starts blooming. Poa annua begins when soil temperatures fall below 70 degrees in the autumn.
Preemergence is essentially a type of herbicide that creates of cloud that kills a freshly germinated seeds. If you can get the timing right for applying these preemergence products, annual weed control is a whole lot easier.
The active ingredient to look for in your preemergence turf herbicides is benefin, oryzalin or pendimethalin. Rotate these products to avoid weeds building a tolerance to one specific chemical. If the label says it is OK to put the product out every 90 days and you don’t mind the expense, do it. It will save you a lot of headaches the rest of the growing season.
Reach Campbell Vaughn, the UGA Agriculture and Natural Resource agent for Richmond County, by e-mailing firstname.lastname@example.org.