University of Illinois Extension

University of Illinois Extension

Hort Answers

Herbicide Injury

Amino Acid (ALS) Inhibitor Herbicide Injury

Chlorimuron (ALS) herbicide drift on Russian sage.
Chlorimuron (ALS) herbicide drift on Russian sage.
varies (1 = very little damage 5 = plants killed)

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

The list below of specific plants is NOT all inclusive. It reflects the authors' experience as well as University of Illinois herbicide injury research trial results.

Plants Affected

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 and fertilize 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

  • Non-Illinois residents: If you are interested in filing a complaint, contact your state pesticide control official via the Association of American Pesticide Control Officials website.

Related Resources
Herbicide Residue Testing Labs
U of IL - Distance Diagnosis through Digital Imaging