University of Arizona a dot Cooperative Extension

Herbicide Symptoms

by Pat Clay, Kai Umeda and Bill McCloskey

Phenoxy and pyridinoxy Auxin-type herbicides

  • Postemergence
  • Foliar absorbed and translocated
  • Also root absorbed
  • Broadleaf weeds


Clarity (dicamba) -

  • Stem twisting
  • Stem swelling

Photo of stem twisting and swelling in cantaloupes.


  • Stem twisting
  • Stem and leaf reddening

Photo of stem twisting, stem and leaf reddening.
(cotton seedlings)


  • Leaf curling and cupping

Photo of leaf curling and cupping on a lettuce seedling.
(lettuce seedling)

Butyrac (2,4-DB) -

  • Stem twisting
  • Necrosis

Photo of stem twisting and necrosis on morninglory.

  • Legumes not as injured as other broadleaves
Photo of cowpeas, cantaloupe and morningglory, showing less injury on cowpeas.
(cowpeas, cantaloupe and morningglory)
  • Leaf strapping

Photo of leaf strapping on cowpea.

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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, Extension Agent, Field & Veg Crops
Kai Umeda, Area Extension Agent, Vegetable Crops
William B. McCloskey, Extension Weed Specialist
College of Agriculture, The University of Arizona, Tucson, AZ.
Material written September 2002.

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Copyright © 2001 University of Arizona,
College of Agriculture and Life Sciences