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HCS Weed Database

College of Food, Agricultural, and Environmental Sciences


Authority Assist

Active ingredients: 
sulfentrazone, imazethapyr
Site of action groups: 
14, 2
EPA reg number: 
Restricted use product or combination: 
Rate (per A): 

Application rates when used in standard PRE or PRE + POST programs, on soils with 2 to 4% OM: coarse-textured - 8 to 10 oz; medium-textured - 10 to 12 oz; fine-textured - 12 oz. Application rate when followed by a POST applica-tion of glyphosate in Roundup Ready soybeans, on soils with 2 to 4% OM: coarse-textured - 4 to 5 oz; medium-textured - 5 to 6 oz; fine-textured - 6 oz. Within a rate range, use higher rates where soil pH is less than 7, and lower rates where soil pH is greater than 7.

Application timing: 

Apply preplant or preemergence, up to 3 days after soybean planting. To minimize risk of crop injury, apply a week or more prior to planting. When applied after planting, apply prior to soybean seed germination to prevent injury to emerging soybean seedlings.


Do not use on coarse soils with less than 1% organic matter, or to soils with pH greater than 7.5. Do not incorporate deeper than 2 inches.

Rotation intervals: 

Time to wait to plant following application (months; NR = no restrictions): corn - 10; wheat - 4; oats - 18; alfalfa - 12; clover - 40; soybeans - NR; tomatoes - 40; popcorn - 18; sweet corn - 18.