Herbicide Injury Symptoms

This information comes from Cooperative Extension
brochure #195021 written in June 1996 by:

Barry Tickes
Cooperative Extension, The University of Arizona

David Cudney
Cooperative Extension, University of California, Riverside

Clyde Elmore
Cooperative Extension, University of California, Davis

Herbicides are applied with the goal of injuring or killing unwanted plants. Many herbicides are selective in that they injure weeds and cause minimal or no disruption of desirable plants. Occasionally, however, desirable plants are injured. This can happen through soil residues of herbicides from applications in previous crops, from spray drift of herbicides moving "off target", or from mistakes in application rates, improper herbicide choice, or improper timing of application. Crop injury can be caused by many factors and may not be due to herbicides, Nutrient deficiencies, salinity, drought, insect, disease, and nematode injury can all produce crop symptoms that can be mistaken for herbicide damage. It is helpful to know what type of injury to expect from herbicides that are commonly used.

In this brouchure herbicides are divided into seven main groups with two of the seven groups further subdivided each having three subgroups. This is similar to the classification method employed in the Herbicide Action Short Course initiated by G.F. Warren and taught each fall at Purdue University. Decisions on grouping were made on the basis of what plant processes were being limited or disrupted by the various herbicides. The groups consist of:

• Growth Regulators
  

• Photosynthetic Inhibitors
  

• Pigment Inhibitors
  

• Lipid Biosynthesis Inhibitors
  

• Amino Acid Synthesis Inhibitors
  

• Inhibitors of Seedling Growth
  

  • Herbicides which disrupt cell division
    

  • Herbicides which inhibit shoot growth
    

  • Herbicides which inhibit both shoot and root growth
    

• Cell membrane disrupters
  

  • Oils, Acids & Salts
    

  • Bipyridylium Herbicides
    

  • Diphenylether Herbicide