How to make your own Insecticidal Soap

Insecticidal soap is a safe, effective way to deal with an insect problem both indoors and out. Unlike pesticides, this simple soap solution is biodegradable, so it won't leave a residue that is harmful to birds or beneficial insects like pollinating bees. Sprayed on an infected plant, it kills only the targeted insects.

There are ready-made insecticidal soaps that you can purchase at most garden supply stores. To apply them, follow the directions on the label. You can also make your insecticidal soap.

When to use Insecticidal Soap:

The fatty acids in this simple soap solution work by disrupting the cell membranes and dissolving the natural waxy coating on soft-bodied insects. Unwanted pests suffocate as a result. Insects that can be treated with insecticidal soap include:

• Spider mites
• Aphids
• Mealy bugs
• Thrips
• Immature White Flies
• Immature Leafhoppers

Aphids. Photo by Ken Sproule

Here's the materials and supplies you need to make your own insecticidal soap:

• Measuring cup
• Funnel (optional– it just makes it easier to pour the liquids into the bottle)
• Tablespoon
• Pure all-natural liquid soap such as Castile soap
• Empty spray bottle (look for one at the Dollar Store)

Ingredients:

2 and 1/3 cup of water (note: hard water can reduce the effectiveness of the soap)

1 tablespoon of pure liquid soap such as Castile soap (Note: don't use dish soap, regular laundry detergent or any soaps with degreasers, skin moisturizers or synthetic chemicals.)

Method:

Remove the top to your empty spray bottle.
Measure the ingredients and using the funnel, pour the them into the spray bottle.
Reattach the lid on the spay bottle and shake the contents gently to combine.
Label the bottle and make sure to store it out of the reach of children.

Before you spray:

Before you begin to apply your spray to an infected plant, there are a few quick things to note.

• Some plants are sensitive to soap sprays, so do a test first. Spray a few leaves or single branch of the plant. Wait a full day to see if there is any signs of burning before proceeding to spray the entire plant.
Sensitive indoor plants include ferns, ivy, succulents, palms, lantana and azaleas. Outdoor plants that might be adversely affected include cherries, plum, Japanese Maple, Bleeding Heart, Ferns, Nasturtiums and Sweet Peas.

• Plants that are stressed should not be sprayed. Don't spray a plant that is wilted and thirsty for water.

• Spray your plant early in the morning when it is cooler and the sun is softer.

• Don't place a plant that has just been sprayed into the bright, hot sun.

Using the Spray:

If it is too cold to work outside, place your plant in the kitchen sink or the bathtub.

Gently shake the bottle to evenly disperse the soap in the water.

Your spray will only work when coming into direct contact with soft-bodied insects, so spray your plant throughly with the insecticidal soap. Turn the plant around in a circle and place the plant on an angle to try to catch all of the leaves including the underside of each leaf.

Thoroughly rinse the soap off after 10 minutes to prevent leaf burn.

Repeat the application of the insecticidal soap once every 4-7 days for a total of three applications to insure that the problem has cleared up.

You might be interested in the article on Unexpected House Pests by Jean Godawa 

on the main gardening blog. 

Many thanks to Ken Sproule and David Cappaert of Bugwood.org for 

providing the photographs of insects.