Postemergence

clethodim (Prism; Select 2C in Oregon only)

Rate Consult label for rate required to control different grasses.

Time Apply to actively growing grasses at recommended weed heights.

Remarks Add crop oil concentrate as described on label.

Caution Consult labels for maximum rate per application and season. Preharvest interval is 14 days.

Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor

Chemical family Cyclohexanedione

halosulfuron-methyl (Sandea)

Broadcast sprays on cucumbers, cantaloupe, processing winter squash, and pumpkins only; directed sprays allowed on other cucurbit crops

Rate 0.023 to 0.047 lb ai/a (0.5 to 1 oz/a) for cucumbers and other cucurbits depending on soil type; 0.023 to 0.035 lb ai/a (0.5 to 0.75 oz/a) for processing winter squash and pumpkins.

Time Apply postemergence to seeded or transplanted crops that are well established and that have two to five leaves (preferably four to five leaves), and before the first female flowers appear.

Remarks Results in the Pacific Northwest indicate potential for crop injury or delayed flowering with broadcast postemergence treatments. Primary use is nutsedge suppression. Applications are allowed for most cucurbit crops if spray is directed to row middles after planting or transplanting, or if applied with shielded sprayers that prevent herbicide contact with the crop. Avoid irrigation or rain within 4 hr after treatment.

Caution Crop growth may be stunted or become yellow briefly after treatment. Consult label for rotation crops, soil-applied organophosphate insecticides, and other precautions. Do not exceed 2 oz/a herbicide per year. Preharvest interval is 30 days for squash, cucumber, and pumpkin, 57 days for melons.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Sulfonylurea

sethoxydim (Poast)

Rate 0.19 to 0.28 lb ai/a (1 to 1.5 pints/a Poast)

Time Apply at optimum growth stage listed on the label.

Remarks Identify susceptible grasses and add 2 pints/a nonphytotoxic crop oil concentrate to improve leaf absorption. Control often is erratic on grasses stunted or stressed from drought, high temperatures, or low fertility. Resistant grasses include annual bluegrass and all fine fescues, but quackgrass can be suppressed. Inhibits fatty acid production, cell membranes, and new growth.

Caution Preharvest interval is 14 days (3 days for cantaloupe). Do not exceed 3 pints/a per season.

Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor

Chemical family Cyclohexanedione