Imazapyr Active Herbicide: A Versatile, Pre- and Post-Emergent Herbicide

Imazapyr active herbicide is a versatile herbicide with a variety of applications in crops, forestry, aquatic and land management. This ALS-inhibiting herbicide is used to control a broad spectrum of grasses, broadleaf weeds, woody brush trees, and floating and emergent aquatic weeds. Its versatility also means imazapyr can be used as a pre-emergent herbicide or post-emergent herbicide. With its residual activity, imazapyr provides control of most newly germinating weeds with post-emergence applications. It is available under the brand names Chopper® herbicide and Arsenal® herbicide.

Key Features and Benefits of Imazapyr

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  • Controls a broad spectrum of grass, broadleaf weed, brush species and aquatic weeds
  • Features exceptionally low mammalian toxicity



  • Can be used in a wide range of applications including row crops, forestry and aquatic vegetation
  • Poses no significant hazard to wildlife

Mode of Action

Imazapyr is an imidazolinone, which is readily absorbed by the roots of weeds. As it moves through the weed, it works by inhibiting the enzyme acetohydroxyacid synthase (AHAS or ALS). This inhibition disrupts protein synthesis and subsequently the cell starves from lack of proteins it needs for growth.

Imazapyr at-a-glance