University of Arizona a dot Cooperative Extension


Herbicide Symptom Key

Aromatic amino acid synthesis inhibitor (inhibition of 5-enolpyruvylshikimate-3-phosphate synthase, EPSPS) - causes a lack of aromatic amino acids (phenylalanine, tyrosine, and tryptophan) that inhibits synthesis of proteins and secondary plant metabolites. Deregulation of the shikimate pathway and uncontrolled flow of carbon into the shikimate pathway removes building blocks from other metabolic pathways.

Symptoms are yellowing and wilting that progress from the new to the older tissues. Can cause deformed leaves and multiple shoots or whorls of narrow or strapped leaves on regrowth in some plants.

glyphosate – (Roundup UltraMax, Rodeo, Touchdown, etc.)

  • Chlorosis followed by necrosis (cowpea)

Photo of dead cowpea plants all bleached out.

 

  • Immediate cessation of growth
  • Stacked nodes (regrowth)

Photo of cotton plants with stacked nodes.

 

  • Interveinal chlorosis at sub-lethal dose

Photo of interveinal chlorosis at sub-lethal dose on corn.

 

Photo of glyphosate caused chlorosis on lettuce seedlings.

Photo of glyphosate caused chlorosis on spinach seedlings.


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.

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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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