Oh, the weeds.
You will rarely hear me complain about rain, except on game days, but these great growing conditions really have the weeds moving. As much as I try not to use pesticides, some weeds just won’t go away.
I am constantly trying to find the right herbicide to apply to unwanted weeds 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 control these weeds can be challenging.
The biggest battle lately is with grassy-type weeds. Common grassy weeds you might be familiar with are Poa annua, crabgrass, nutsedges, bahia, dallisgrass, and wild garlic/onion.
Like most plants, lawn weeds are divided into perennials and annuals. With perennial grassy weeds, they establish and stay with us year after year. They take up residence and don’t want to leave. Depending on the turf type, these perennials are hard to fight. Annual weeds live fast and die after one growing season.
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 post-emergence grassy weed control in our turf grasses. 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 nutsedge, 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 that another benefit of this product is being able to overhead spray junipers, liriope, Indian Hawthorne, mondo grass, Asiatic jasmine, and a host of other ornamentals for various weed control.
As a precaution, Image has several available herbicides, so when purchasing, make sure you are buying the correct Image product. MSM Turf (metsulfuron methyl) is the best homeowner product available for controlling bahiagrass. And like Image with imazaquin, MSM Turf controls a bunch of other weeds as well.
All three of these products I mentioned here are labeled to spray on all our four warm season turf grasses.
Annual weeds come from seeds that blow in from the wind, cars driving down your street, or 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 annual grass. Once these weeds are up, the challenge begins. For instance, the chemical quinclorac will kill crabgrass graveyard dead only in Zoysia and Bermuda, but in St. Augustine and centipede grass, quinclorac is lethal to your expensive turf. But quinclorac doesn’t treat for Poa annua. Atrazine will wipe out 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 of annual weeds is always going to be a pre-emergence 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 a cloud that kills freshly germinated seeds. If you can get the timing right for applying these pre-emergence products, annual weed control is a whole lot easier. Usually that means in the spring, apply by at least March 1, and in the fall for cool-season weeds, apply by Sept. 1.
Some of the active ingredients to look for in your pre-emergent turf herbicides are benefin, oryzalin, prodiamine, 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 for the rest of the growing season.
This article originally appeared on Augusta Chronicle: Timing weed treatments right can prevent headaches | Exclusive
