Postemergence control of labeled grass weeds in greenhouses, lathhouses, shadehouses, and around outdoor ornamentals, including nurseries, parks, Christmas or other tree farms, roadside plantings, and landscaped areas around buildings. Note: the 2EC formulation is labeled for conifer production, not for nursery or landscape uses.

Many annual and some perennial grasses such as barnyardgrass, crabgrass, crowfoot grass, foxtails, field sandbur, bermudagrass, johnsongrass, and quackgrass.

Sedges and broadleaf weeds.

Apply to actively growing grasses that are not under environmental stress. Repeated applications are required for control of perennial grasses. See specific label for recommended adjuvants. Add a nonionic surfactant (containing at least 80 percent active ingredient) at 0.25% by volume to the spray solution (1⁄₃ oz per gallon). Or, add crop oil concentrate at 1 pt/A. Consult label for appropriate application timing for perennial grass control.

Unsatisfactory control may result if grasses are stressed by drought, temperature extremes, excessive water, or low humidity, or if grasses are not at the correct growth stage at the time of application. Do not cultivate treated grasses seven days before or seven days after application or control may be reduced. Do not apply a broadleaf herbicide within one day following clethodim application. Do not apply clethodim if rainfall is expected within 1 hour of application. Sugar maples cannot be tapped for syrup within one year of application. Do not apply more than 68 fluid ounces (0.5 pound active ingredient) per acre per season. Growers have reported some injury on Blue Ice cypress, Asiatic lily, Emerald arborvitae and Arizona cypress. Flowers on landscape plants contacted by the spray can be damaged, but no impacts on subsequent flowering have been reported.

No residual weed control should be expected.

Little volatility. Clethodim is rapidly degraded through activity of microbes and exposure to sunlight. The chemical is only slightly adsorbed and has the potential to leach, but degradation is very rapid so the actual amount of leaching is probably slight.

Slow acting herbicide; requires 7 to 14 days for control. Grass weeds will have slowed growth within a few days, followed by chlorosis of the emerging leaves, then a general decline. Inhibits acetyl coenzyme A carboxylase, an important enzyme for many biosynthetic pathways. MOA Group 1.

Herbicide injury symptoms factsheet