Proper post-application procedures
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Proper post-application procedures

Features - Weed Control // BMPs

Best management practices don’t end when herbicides are applied. Be sure you’re following through with certain tasks.

January 10, 2022

Part of a smart weed control strategy includes chores that should be done after herbicide applications are complete.

Keep application records

Every time a chemical of any type is applied, a complete record of the application should be made. Pesticide records will be the basis for any changes that may be needed in the pest/weed control program. If the material did not work, the records could indicate why. A change in the time or rate of application, the application technique, or the chemical used may be required. If the crop was injured, well-kept records will help determine what changes must be made to prevent additional problems in the future.

The records should include:

  • Application date
  • Chemical
  • Formulation
  • Application rate
  • Area covered
  • Amount of product applied
  • If sprayed, volume of water applied
  • Weather (temperature, clear or cloudy, time to next precipitation of at least 0.5 inch)
  • Growth stage of weeds
  • Growth stage of the crop
  • Comments on any problems at the time of application (e.g., clogged nozzle, broken spray line)


Soil treated with most preemergence herbicides can be cultivated to a depth of 1.5 inches without reducing weed control. Cultivating deeper than 2 inches reduces the effectiveness of all herbicides. Soil treated with oxadiazon or any herbicide containing oxyfluorfen should not be cultivated following treatment.

Clean the sprayers

Immediately after being used, sprayers should be cleaned. Flush the system with clean water, including spraying water through all of the lines and nozzles. Rinse the sprayer with a detergent solution. Next, rinse again with clean water.

Sprayers used for applying oil-based compounds should be cleaned as follows:

  • Flush the entire system with a detergent solution.
  • Fill the tank and prime the spray system with a 10 percent ammonia solution (1 gallon of household ammonia in 10 gallons of water) and let it stand for 12 to 24 hours.
  • Disassemble the nozzles and soak the caps, screens, etc., in the ammonia solution.
  • Rinse thoroughly with water and circulate it through the sprayer.
  • Test spray a few susceptible plants, such as tomatoes or peppers, at least four days before using the sprayer on crops.
  • If the herbicide label includes cleaning instructions, follow them.

Sprayer and herbicide storage

After cleaning, drain the spray lines, pump, and tank. To prevent the pump from rusting and freezing, fill it with oil or some other suitable lubricant. Sprayers should be stored in a dry location. Remove nozzles, caps, screens, etc. from the sprayer, cleaned, and stored in clean cloth bags.

Store herbicides in a locked dry area. Keep herbicides in their original containers and make sure the label is not damaged or removed. Do not allow herbicides in liquid form to freeze.

About the author: Jim Sellmer is a professor of ornamental horticulture at Penn State. Read Sellmer’s entire weed control publication here: