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Ministry of Agriculture, Food and Rural Affairs


Trade Names: Conquest B, Pursuit

Group 2

Site of Action: Inhibitors of acetolactate synthase (ALS) and also called acetohydroxyacid synthase (AHAS)

Following POST emergent application:

  • Within an hour the inhibition of ALS enzyme leads to a rapid cessation of cell division and plant growth
  • Within 1- 2 weeks symptoms become visible
  • Meristematic regions are the first to experience chlorosis and necrosis followed by general foliar chlorosis and necrosis

Uptake and Translocation

  • Absorbed by both roots and foliage
  • Translocation in both xylem and phloem


  • Depends on weather and soil conditions (more persistent under dry conditions)
  • Half-life in field: 60- 90 days
  • For most vegetable crops, a 22 month recropping interval is recommended

Photographs courtesy of:

F.A Holm and Ken Sapsford at University of Saskatchewan - Department of Plant Sciences - Weeds Research - Herbicide Injury Symptoms:


Imazethapyr Imazethapyr injury on brassica Imazethapyr injury on tomato Imazethapyr injury on strawberries ImazethapyrImazethapyr injury on hempnettleImazethapyr injury on stinkweedImazethapyr injury on wild buckwheatImazethapyr injury on wild buckwheatImazethapyr injury on wild oat Imazethapyr injury on potatoClick to enlarge.