Controlling Weeds in Nursery and Landscape Plantings

Bulletin 867

Procedures After Herbicide Applications

Keeping application records

Every time a pesticide 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 control program. If the material did not work, the records could indicate why. A change in the time or rate of application, 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:

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

Cultivating

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 Ronstar or any herbicide containing oxyfluorfen (Goal, OH2, Rout, Regal O-O) should not be cultivated following treatment. They form a chemical barrier on the soil surface that burns off weed seedlings as they emerge, and they need light to be active. Anything that breaks that soil barrier or covers the herbicide layer will reduce their effectiveness.

Cleaning sprayers

Immediately after being used, sprayers should be cleaned in the following manner:

1. Flush the system with clean water, including spraying water through all of the lines and nozzles.
2. For more thorough cleaning, rinse the sprayer with a detergent solution.
3. Rinse again with clean water.

It is difficult to remove oil-based compounds such as 2,4-D or Garlon 4E from sprayers. Sprayers used for applying these compounds should be cleaned as follows:

1. Flush the entire system with a detergent solution.
2. Fill the tank and prime the spray system with a 10% ammonia solution (1 gallon of household ammonia in 10 gallons of water) and let it stand for 12 to 24 hours.
3. Disassemble the nozzles and soak the caps, screens, etc. in the ammonia solution.
4. Rinse thoroughly with water and circulate it through the sprayer.
5. Test spray a few plants known to be susceptible, such as tomatoes or peppers, at least 4 days before using the sprayer on crop plants.

If the herbicide label includes cleaning instructions, follow them.

Storing sprayers and herbicides

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. Nozzles, caps, screens, etc. should be removed from the sprayer, cleaned, and stored in clean cloth bags.

Store herbicides in a locked dry area out of the reach of children and pets. 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.