Ronald Strahan, Koske, Thomas J.
Herbicides can reduce weeds in your turf, but thick sod keeps weeds out. Your county agent can advise you in your weed control plan. Apply herbicides either before or several weeks after first green-up but not during first greening up. Some herbicides should not be used on certain grass types (read labels thoroughly).
Broadleaf weeds often can be controlled by using selective postemergence blends that contain two or more herbicides. Formulations of 2,4-D or blends with 2,4-D are available for most southern grasses, but be extra careful using it on St. Augustine lawns. Examples of these products are Bayer Advanced Southern Broadleaf, Ortho, Weed B Gon, Spectracide Weed Stop, Trimec or Fertilome Weedfree Zone.
Manor or Blade herbicides easily control bahiagrass in Bermuda, centipede, St. Augustine or zoysia grasses.
Most labels will stress use on younger weeds growing in the cooler midspring. A temporary discoloration of the lawn may occur. A second application two or three weeks later is usually needed (sometimes a third). Wet the foliage only; don’t saturate the soil. Control weeds NOW, in spring! Mow herbicide-treated lawns several times without a bag before collecting clippings for compost or mulch. Read and follow label directions! Some products contain phenoxy (2,4-D) herbicides. Avoid drift and keep spray away from gardens.
Clean these sprayers thoroughly with an ammonia solution if the sprayer is used with plant protectants on good plants. It is best to buy a sprayer only kept for weed killers.
For Bermuda or zoysia lawns only, weed killers with MSMA or DSMA often provide good selective control for most grassy and some broadleaf weeds. Use these two arsenicals when weather is well warm as in June through August.
Preemergence herbicides can be applied to thin lawns to protect them from weeds until they thicken and cover. These PreEs are not for newly seeded areas or areas with growing weeds because they work on seedlings only.
Some home PreE are Greenlight Crabgrass Preventer, StaGreen Crabex, Hi Yield Dimension, Scott’s Halts, Portrait, Atrazine and Crabgrass Preventer 2.
It is often said that your weed control is only as good as your application, but you also must have an appropriate material for the time, turf and target species.
The LSU AgCenter and the LSU College of Agriculture