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University of Illinois Extension

Plant Growth Regulator (PGR) Herbicide Injury

Purple coneflower plant as affected by PGR herbicide drift.

Purple coneflower plant as affected by PGR herbicide drift.  


Can vary (1 = very little damage 5 = plants killed)


Not specific to a particular plant. Dicots are primarily affected.

The list below of specific plants is NOT all inclusive. It reflects the authors' experience as well as University of Illinois herbicide injury research trial results.    


The growth regulator compounds mimic different growth regulating compounds in the plant and may cause a variety of growth abnormalities in susceptible species. The injury symptoms generally are first seen in the newly developing tissue or leaves.

Benzoic Acids: dicamba (Banvel, Clarity, and a component of Marksman and Distinct)

Phenoxyacetic acids: 2,4-D, 2,4-DB, MCPP, and MCPA.

Pyridinecarboxylic acids: clopyralid (Stinger, Lontrel, and a component of Curtail), fluroxypyr (Starane, Spotlight, and Vista), picloram (Tordon) and triclopyr (Garlon and Turflon Ester).

Characteristics of activity:

Symptoms of Injury:


Filed under problems: Herbicide Injury

More information is available on Hort Answers.