University of Arizona a dot Cooperative Extension

Herbicide Symptom Key

by Pat Clay and Bill McCloskey

Guide to Herbicide Injury Symptoms on Crops and Weeds

Determining if problems in the field are related to herbicides or other factors is difficult at best. Many plant diseases, fertility problems, and environmental factors can be confused for herbicide injury. If herbicides are involved, having a basic understanding of how herbicides are used, move in plants, and effect plant processes can be of assistance in narrowing down the injury to a family of herbicides if not an individual material.

The following guide is setup to give a basic understanding of typical symptoms that occur for many of the herbicides available for use in Arizona.

I. Herbicide applied exclusively to the soil - injury appeared as the weed/crop emerged or did not emerge

II. Herbicides with significant foliar use - classified by translocation pattern - some herbicides in this group are exclusively applied to foliage while others can be applied to foliage but are more commonly applied to soil

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
William B. McCloskey, Extension Weed Specialist
College of Agriculture, The University of Arizona, Tucson, AZ.
Material written June 2003.

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