Halosulfuron is the active you want. It is the only home-garden option rated good to excellent on both yellow and purple nutsedge, so it covers you either way. Bentazon, imazaquin and sulfentrazone each fall down on one species or the other. That makes it the best nutsedge killer for most home lawns, as long as the label covers your turf type and your site. Read the ingredient line on the back of the jug before you pay, because brand names shift around and the active is the part that does the work.
"Same jug, same weekend, and mine died and yours did not." My neighbor told me that over the fence with a bottle of bentazon in his hand. His sedge was yellow nutsedge, where bentazon rates good. Mine was purple, where the same product drops to poor. I had worked my own patch for three seasons and never once asked which sedge I was dealing with. One jug, two lawns, the same label on both, and only one of us got a dead patch out of it that summer.
The two sedges are separate species, and the ratings split right along that line. UC IPM counts only four of these actives on the home-gardener shelf, and two of them sit in the table above. It also warns that no product controls mature plants well, so your timing counts as much as the active you pick. Halosulfuron for nutsedge pays off on young shoots, while the plant still hauls the chemical down into its tubers. Spray a big old stand instead and you are aiming at the hardest target in the yard.
Speed differs too. Penn State sprayed sulfentrazone on yellow nutsedge in early July and saw injury in 2 days. The treated plants had vanished at 10 days. Halosulfuron in that same trial did nothing you could see for about a week, and the plants dried out fully at three weeks. Those numbers come from one application on one species, so read them as observations and not as a schedule. Green sedge a week after you spray a halosulfuron product is normal, and pulling it out early wastes the treatment.
Two rules keep that spray working for you. Clemson calls for a nonionic surfactant at 2 teaspoons per gallon (10 ml per 3.8 L), plus a repeat treatment in 6 to 10 weeks. North Carolina State Extension found that two sprays at the lower rate beat one spray at the higher rate, and it caps you at two applications per year. Your own label sets the rate for your formulation and your grass, so read it before you mix anything in the tank.
Do not apply postemergence herbicides in hot, dry weather above 90°F (32°C). Wait for a cooler stretch and spray then.
Match the sedge herbicide to the species in your lawn, then spray it while the shoots are young. If you know the patch is yellow nutsedge, bentazon rates good on it. If the patch is purple, or you cannot tell the two apart from across the lawn, the best nutsedge killer on your shelf should be halosulfuron. Add the surfactant and the second pass, then leave the patch alone for three weeks before you judge how well the spray worked. New shoots after that point are your cue to line up the repeat treatment, not to go buy a stronger jug.
Read the full article: Nutsedge: How to Kill It and Keep It Out
