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 on.
• Chlorosis/necrosis of plant tissue.
• Drift injury occurs as speckling on leaves.

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 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.