University of Arizona a dot Cooperative Extension


Herbicide Symptom Key

Photosystem I energized cell membrane destroyers - these herbicides accept electrons from PS I and produce hydroxyl radicals (OH*) that result in rapid lipid peroxidation and membrane destruction.

Symptoms: rapid development of "water soaked" appearance followed by dessication and necrosis.

Bypyridilium herbicides

paraquat - Gramoxone Max diquat - various trade name

  • Rapid desiccation of leaf tissue (on purslane)

Photo of desiccated purslane plants.

  • Leaf tip burn (on corn)
  • Necrotic lesions

Photo of a corn plant with tip burn and necrotic lesions.

  • Necrotic spots with red halo (on cotton)

Photo of cotton plant with necrotic spots on the leaves.

Full Disclaimers

Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director Cooperative Extension, College of Agriculture, The University of Arizona.

The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.

Because labels are subject to frequent change, always consult the label attached to the product before using any pesticide. The user must assume responsibility for proper application and for residues on crops as well as for damage or injury caused by pesticides, whether to crop, person or property.

Any products, services, or organizations that are mentioned, shown, or indirectly implied in this web document do not imply endorsement by The University of Arizona.

Erin Taylor, etaylor@cals.arizona.edu Extension Agent, Field & Veg Crops
William B. McCloskey, wmcclosk@ag.arizona.edu Extension Weed Specialist
College of Agriculture, The University of Arizona, Tucson, AZ.
Material written June 2003.


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