Herbicide Injury Symptomology: Growth Regulator Injury

Benzoic Acids, Phenoxy Acetic Acids, and Pyridines


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Benzoic acids

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Trade Names and Uses:

  • Banvel (Dicamba)
    -corn, grain sorghum, wheat, pastures
  • Clarity (Dicamba)
    -corn, grain sorghum, wheat, pastures

Injury Symptoms: Malformation or necrosis of terminal meristematic areas, stem twisting and epinasty, early petioles turned down, and leaves cupped upward. Broadleaf plants may exhibit more cupping than strapping of leaf tissue. Benzoic acids are more toxic to soybeans than phenoxy's with leaves turned up.

Phenoxy Acetic Acids

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Trade Name and Uses:

  • 2, 4-D
    -corn, grain sorghum
  • 2, 4-DB
    -soybeans, alfalfa

Injury Symptoms: Abnormal growth responses with youngest leaves being strap-shaped and cupped upward and twisted; brittle, branched, and/or developcallous tissue on stems. Corn plants exhibit rolled leaves (onion-leafing), fused brace roots, stalk bending, brittleness and missing kernels. Small grains exhibit twisted flag leaves, sterile florets or multiple florets. More strapping occurs with phenoxy acetic acids than the benzoic acids.

Pyridines

Trade Names and Uses:

  • Stinger (Clopyralid)
    -corn, pastures
  • Garlon/Rely (Triclopyr)
    -pastures, rice

Injury Symptoms: Growth regulator, malformation or necrosis of terminal meristematic areas, stem twisting and epinasty, early petioles turned down, and leaves cupped upward. Broadleaf plants may exhibit more cupping than strapping of leaf tissue.


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