University of Illinois Extension
University of Illinois Extension - Selecting Trees for Your Home
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Photosynthesis (PSI and PSII) Inhibitor Herbicide Injury
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Atrazine herbicide drift on pumpkin (cucurbit).
Severity: out of 5
Frequency: out of 5
Symptoms:

These herbicides all inhibit photosynthesis in susceptible plants.

Triazines: atrazine (numerous premixes), metribuzin (Sencor), and simazine (Princep).

Characteristics of activity:

  • Translocated in xylem.

Symptoms of injury:

  • Leaf margin burn and interveinal chlorosis.
  • Older leaves affected first.

Benzothiadiazoles: bentazon (Basagran), Phenylpyridazines: pyridate (Tough), and Benzonitriles: bromoxynil (Buctril)

Characteristics of activity:

  • Limited translocation.

Symptoms of injury:

  • Necrotic spots, speckles chlorosis, or bronzing.
  • Activity and injury increase with temperature.

Bipyridiliums: paraquat (Gramoxone Max, Gramoxone Extra, Gramoxone Inteon) and diquat (Reward).

Characteristics of activity:

  • Nonselective
  • Very little translocation.

Symptoms of injury:

  • Water-soaked look early.
  • Chlorosis/necrosis of plant tissue.
  • Drift injury occurs as speckling.
Cycle:
Management:
  • Read and follow all label directions.
  • Use caution when applying herbicides around plants as desirable plants may be sensitive and injury may result.
  • Do not spray during cool, wet weather as herbicide is metabolized slower at these times.
  • 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.
Associated trees: