Postemergence

clethodim (Prism; Select 2C in Oregon only)

Rate 9 to 16 fl oz/a for annual grasses; 12 to 16 oz/a for perennial grasses at 0.25% v/v

Time Apply to actively growing grasses at recommended weed heights.

Remarks Add non-ionic surfactant (NIS) at 0.25% v/v. Maximum 4 applications or 64 fl oz/a per year. 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 for 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. Crop rotation intervals are up to 24 months for beets and spinach and 18 months for many crops of the mustard family 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.

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