Soap Flush Test for Pests (like Fall Armyworms)

How to Perform the Soap Flush Test for Insect Pests in Lawns

A soap flush is a mixture of 3 tablespoons of liquid dish soap with 1 gallon of water. We find that lemon-scented dish soap is the most effective. 

Pour the mixture into a 3' x 3' area and watch the action. The soap will agitate the caterpillars' skin and they will come to the surface - you can see them and then you will know to treat for them immediately.

Soap Flush Test Recipe

  • 3 tablespoons liquid dish soap (lemon scented)
  • 1 gallon of water
  • bucket or large container

We recommend scouting for fall armyworms from July until the first good frost in autumn.

If the soap flush doesn't flush out any caterpillars, try it again under different circumstances such as :

  • try a different time of day
  • if you did the test in an area with damage, they may already be gone from that area, so try again along the border of the damage

This test also works for many other destructive insects.

If you have fall armyworms, read our article focusing on what to do about them: Fall Armyworms in Lawns.

armyworm soap flush Caleb Kearney
This is an example of what you'll see in the soap flush test: armyworms will come to the surface so you can verify that you have an infestation.


Case Study on Soap Flush Test

Mark in Georgia purchased 2 pallets of Bermuda on August 17th. On September 12th we discovered Mark had fall armyworms. To confirm that was the problem, he performed the Soap Flush Test we recommend.

The test was positive, so he applied armyworm insecticide, and this is what it looks like now! Mark stated that “Your tip on the army worms was a lifesaver! I showed the pics to several people and they also never knew about those armyworms (and how to test for them!)”


Damage caused by fall armyworms.
Damage caused by fall armyworms


shows full recovery of Bermudagrass after fall armyworm infestation
Full recovery after treating for fall armyworms    

Soap flush test for insects fall armyworm