Amino Acid Inhibitor Herbicide Injury


Mostly affects broadleaf plants; however, some grassy plants can also show injury.


These herbicides inhibit key enzymes in various amino acid synthesis pathways.

  • Imidazolinones: imazaquin (Scepter, Image), imazapic (Plateau), imazapyr (Arsenal, Chopper), imazethapyr (Pursuit), imazamox (Raptor).
  • Sulfonylureas: chlorimuron (Classic), primisulfuron (Beacon), thifensulfuron (Harmony GT), nicosulfuron (Accent), halosulfuron (Permit, Sedgehammer), and tribenuron (Express).
  • Triazolopyrimidine sulfonanilides: flumetsulam (Python) and cloransulam (First Rate)

Characteristics of activity

  • Translocation in both xylem and phloem.

Symptoms of injury

  • Stunted plants.
  • Leaf yellowing or chlorosis of leaf margins, purpling of new leaves first.
  • Slow plant death.
  • Early symptoms may appear similar to potassium deficiency.  


  • Read and follow all label directions.
  • Use caution when applying herbicides around plants as desirable plants may be sensitive and injury may result.
  • Do not spray during cool, wet weather as herbicide is metabolized slower at these times.
  • Do not spray when wind speed and direction are such that herbicide drift is likely to occur.
  • Affected plants may or may not survive herbicide drift; it depends on both the degree of exposure and the plant's tolerance to the herbicide.
  • Water plants as needed to promote good plant health.
  • Illinois residents: If you suspect herbicide injury as a result of off-target movement from a nearby application and you are interested in filing a complaint with the Illinois Department of Agriculture, call the Illinois Department of Agriculture's Bureau of Environmental Programs at 1-800-641-3934. To learn more about spray drift and the formal complaint process, visit the Illinois Pesticide Safety Education Spray Drift Resource.