University of Illinois Extension

University of Illinois Extension

Hort Answers

Herbicide Injury

Plant Growth Regulator (PGR) Herbicide Injury

Purple coneflower plant as affected by PGR herbicide drift.
Purple coneflower plant as affected by PGR herbicide drift.
 
Severity
Can vary (1 = very little damage 5 = plants killed)
 
Hosts

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.

 
Plants Affected

Annual

Shrub

Small Fruit

Tree

Vegetable

Vine

 
Symptoms

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:

  • Translocated in both xylem and phloem.

Symptoms of Injury:

  • Stunting and cupped-shaped crinkled leaves.
  • Twisting of stems and petioles.
  • Leaf strapping,puckering, parallel venation. (associated with pyridinecarboxylic acids).

 
Management
  • Read and follow all label directions.
  • Use caution when applying PGR herbicides around broadleaf plants as desirable plants may be sensitive and injury may result.
  • Do not spray when air temperature and/or humidity is high or is expected to be high.
  • Do not spray when wind speed and direction are such that herbicide drift is likely to occur.
  • Affected plants may or may not survive herbicide drift; it depends on both the degree of exposure and the plant's tolerance to the herbicide.
  • Water and fertilize plants as needed to promote good plant health.
  • Illinois residents: If you suspect herbicide injury as a result of off-target movement from a nearby application and you are interested in filing a complaint with the Illinois Department of Agriculture, call the Illinois Department of Agriculture's Bureau of Environmental Programs at 1-800-641-3934. To learn more about spray drift and the formal complaint process, visit the Illinois Pesticide Safety Education Spray Drift Resources website.
  • Non-Illinois residents: If you are interested in filing a complaint, contact your state pesticide control official via the Association of American Pesticide Control Officials website.

 
Related Resources
Herbicide Residue Testing Labs
U of IL - Distance Diagnosis through Digital Imaging