Quackgrass and Other Perennial Grasses

atrazine

Rate Consult label

Time Apply in fall or, preferably spring either as a single application at higher rates 1 to 3 weeks before plowing to actively growing quackgrass or as a split treatment, first before plowing and second before, during, or after planting, before weeds are 1.5 inches tall.

Remarks Adding a nonionic adjuvant enhances control. Control of wild proso millet is poor. See label for planting sensitive crops within 12 to 24 months, depending on time of application and total applied. Select other herbicides with reduced soil persistence to reduce carryover.

Caution A restricted-use herbicide. Do not graze treated area or feed treated foliage to livestock for 45 days after treatment.

Site of action Group 5: photosystem II inhibitor

Chemical family Triazine

glyphosate (numerous trade names)

Rate Consult labels.

Time Spot-treat vigorously growing quackgrass 6 to 8 inches tall by eliminating both the weed and crop within the treated area.

Remarks Spray before corn silks to avoid residues in the harvested crop. Inhibits production of three amino acids and protein synthesis.

Caution Do not treat more than 10% of the acreage.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

sethoxydim (Poast)

Poast-protected sweet corn varieties only

Rate Consult label; maximum rate is 0.28 lb ai/a (1.5 pints/a) with a maximum of 0.56 lb ai/a (3 pints/a) per year.

Time Maximum height for quackgrass and wild proso millet control is 8 and 10 inches, respectively.

Remarks Use in Poast-protected sweet corn varieties only, such as Rogers GH 2042, GH 6333, and GH 6631. May be applied over the top. A second application is allowed 10 days after the first. Identify susceptible grasses and add 2 pints/a non-phytotoxic 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; quackgrass can be suppressed. Grass control may be reduced if applied with bentazon. Inhibits fatty acid production, cell membranes, and new growth.

Caution Do not apply to corn hybrids that are not tolerant to Poast. Do not exceed 3 pints/a per year. Preharvest interval is 30 days.

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

Chemical family Cyclohexanedione