WSSA Resistance Group: 2
Crop/non-crop registration: Field and seed corn, grain sorghum
Sensitive weeds: Annual BLW (broadleaf weeds): cocklebur, velvetleaf, ragweed, wild mustard, redroot pigweed, Venice mallow, yellow nutsedge.
Application method: POST- in corn, from spike stage to 10 leaf stage (typically before crop is 50-76 cm tall (20-30").
Absorption & Translocation: Following foliar absorption, halosulfuron is rapidly absorbed through the leaves and translocated via both 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;following growth inhibition, meristematic areas gradually become chlorotic and necrotic, followed by a general foliar chlorosis and necrosis with complete control typically occurring within 1-2 wks.
Residuality: Intermediate (1- 4 months).
Toxicity: Oral LD50 = >1287 mg/kg - slightly toxic.
Additional comments: When early POST treatments are used in corn, sequential applications may be required to control later weed flushes; following application to foliage, allow 30 days before grazing domestic livestock, harvesting forage, or harvesting silage; halosulfuron can be tank mixed with a number of grass herbicides (atrazine, dicamba, nicosulfuron) to increase the spectrum of control.
