Herbicide Injury Symptomology: Amino Acid Synthesis Inhibitors

Imidazolinones

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Trade Name and Uses:

• Arsenal (Imazapyr)
  -noncropland
• Lightning (Imazethapyr + Imazapyr)
  -corn
• Pursuit (Imazethapyr)
  -soybeans, alfalfa, IT/IR corn
• Raptor (Imazamox)
  -soybeans
• Scepter (Imazaquin)
  -soybeans

Mode of Action: Inhibition of ALS or AHAS enzyme (acetohydroxyacid synthase).

Injury Symptoms: Soil and foliar activity - kills slowly, loss of apical dominance, chlorosis, and shortening of internodes. Grass plants may be stunted with chlorosis or purpling. Corn plants may be stunted and show symptoms of root inhibition such as pruning of lateral roots. Leaves emerging from the corn whorl may not unfurl properly and be yellow to translucent in appearance. Broadleaf plants may be stunted and chlorotic or purple. Soybean injury can range from stunting to death of terminal growing point. Soybean leaves may be yellow in appearance and leaf veination may appear red or purple in color.