How to Make Insecticidal Soap to Spray on My Plants

Updated February 21, 2017

Nothing is more frustrating for gardeners than spotting insects and pests on well-tended plants. Insects such as aphids, spider mites and thrips, to name a few, can quickly kill a plant if they are not eliminated. One method of killing plant insects is by using an insecticidal soap, which smothers the insects. Although you can purchase insecticidal soap at any home and garden centre, you can also make your own.

Fill a large spray bottle with 1 qt. of plain tap water.

Add 1 tbsp of liquid soap to the spray bottle and screw on the sprayer attachment. Choose only a soap that has no dye or fragrance added.

Shake the bottle once or twice to distribute the soap, but try not to create many bubbles. The solution will be slightly cloudy.

Re-open the spray bottle and add 1/4 cup of vegetable oil such as corn, canola or safflower. Replace the spray bottle top and shake the contents again.

Take the spray bottle outside to the infested plants. Aim the nozzle at the plant and spray the insecticidal soap solution directly onto any visible insects.

Kneel down on the ground, or bring the plant to eye level, and spray the underside of the leaves with the insecticidal soap solution.

Wait one week and examine the plant for signs of insect activity. If insects are still visible, respray the plant with your homemade insecticidal soap.


Do not spray the plants more than once a week to prevent damage. To treat Colorado beetles, cucumber beetles, caterpillars and other hard-to-control insects, add an additional 1 to 2 tsp of ground chilli pepper to the mixture. Test this spray on a small area of the plant first to ensure that it does not burn the leaves.

Things You'll Need

  • Spray bottle
  • Water
  • Liquid soap without dyes or fragrance
  • Vegetable oil
  • Ground chilli pepper (optional)
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About the Author

Kimberly Johnson is a freelance writer whose articles have appeared in various online publications including eHow, Suite101 and Examiner. She has a degree in journalism from the University of Georgia and began writing professionally in 2001.