Pursuit / imazethapyr

WSSA Resistance Group: 2

Crop/non-crop registration: Soybeans, beans, imidazolinone-resistant (IR) corn, alfalfa for seed

Sensitive weeds: Many annual BLW (broadleaf weeds) species and several annual grasses, especially when applied PPI, PRE, or early POST (2-leaf stage of weeds): green and yellow foxtails, barnyardgrass, witchgrass, cocklebur, velvetleaf, common ragweed, wild mustard, redroot pigweed, lambsquarters, smartweed.

Application method: Early PREPLANT, PPI, PRE, and POST.

Absorption & Translocation: Readily absorbed by foliage;root absorption also occurs but is slower; translocated via both the xylem and phloem.

Mode of Action: Inhibition of acetolactate synthase.

Metabolic pathway inhibited: Inhibits acetolactate synthase (ALS), also called acetohydroxyacid synthase (AHAS), a key enzyme in the biosynthesis of the branched-chain amino acids isoleucine, lecucine, and valine.

Basis of Selectivity: Metabolized by tolerant species to non-phytotoxic compounds.

Symptoms: Growth of treated plants is inhibited within a few hours after application and susceptible weeds are no longer competitive with the crop; injury symptoms usually appear 1-2 wks after application; following growth inhibition, meristematic areas gradually become chlorotic and necrotic, and this is followed by a slow general foliar chlorosis and necrosis.

Residuality: Intermediate-long (4-6 months) depending on weather and soil conditions (more persistent under dry conditions); see additional comments section below.

Toxicity: Oral LD50 = >5000 mg/kg - practically non-toxic (PURSUIT = >5000 mg/kg - practically non-toxic).

Additional comments: Rotational cropping restricted to soybeans, white and kidney beans, processing peas, corn, spring barley, spring wheat, and winter wheat (but for this latter crop, a period of 100 days is required between application of imazethapyr and planting); do not plant other crops the year following application as injury may result; can be applied up to 30 days prior to planting; can be used in reduced and no-till situations; POST applications require the addition of a surfactant and liquid fertilizer solution for maximum efficacy; temporary soybean discoloration and/or stunting may occur with POST applications.