Kill Insects and Mites with Insecticidal Soap

Insecticidal soap is the most effective non-toxic treatment against soft-bodied insects on houseplants. It is environmentally safe and poses no threat to humans and pets.

It is made of potassium fatty acids that penetrate the waxy covering on soft-bodied insects such as aphids, mites, mealybugs, scale, thrips, and whiteflies. The spray works as a contact insecticide which must be applied directly on the insect. This causes excessive water loss and the plant bugs die from dehydration.

These sprays are effective only when they have direct contact with the insects. When the soaps dry, they are no longer potent and will have no effect. For example, spraying only the upper leaf surface will leave whiteflies alive and healthy because they usually feed on the undersides of the leaves. While in the immature stages they become fixed to the
host plant and will not be killed by contact with the wet solution.

You can purchase these soaps from the garden center or you can make your own homemade version.

Homemade Soap Spray Recipe

1.  Make sure you use pure soap when following homemade recipes, as detergents have changed over the years. Avoid the ones that have additives such as bleach, grease cutters and other hazardous ingredients and chemicals. You don't want to do any thing that may burn the plant leaves.

2.  Use one tablespoon of liquid soap per gallon of water

Tip: Always Use soft water or demineralized water for your homemade soap recipe.  Hard water is unsatisfactory because it will cause soap scum to build up on plants.

3.  Combine ingredients in a bucket, mix, then transfer to a clean spray bottle to use as needed.

It will not work as a deterrent and should not be applied as a preventive measure. Once the spray has dried, an insect will not be harmed by walking over the residue. Spray only when and where there is an infestation.

Check for Signs of Pests

Symptoms such as leaf or shoot distortion, sooty mold, and holes in leaves require a further investigation to determine the cause and the extent of an infestation. Spray evenly on all surfaces of the plant for one month to control ongoing infestations,  so that they do not get a chance to damage plants any further.

Sign of Soap Damage (Phytotoxicity)

Watch sign of phytotoxicity which is an adverse plant reaction, or injury, from the soap treatment. Symptoms include yellow or brown spotting on foliage, “burned” tips, and yellow or brown scorching on leaf edges.

Soap spray may also cause marking on certain pome (e.g., apple, pear) and stone fruit varieties.


How to Prevent Plant Injury

1. Do not use the insecticidal soap spray on plants that are under stress. Drought is a major stress factor. Newly planted ornamentals, transplants, or newly rooted cuttings are under stress and should not be sprayed until they are well established. Conifers are particularly susceptible when under drought stress. Make sure plants are well watered before treatment.

2. Avoid treating sensitive plants

3. Test your solution on a small portion of the plant first, as Some plants are sensitive to soap solutions.

3. Apply during the cool times of day to lessen foliage damage.

4.  Spray evenly on all plant surfaces and repeat weekly for at least one month.  You will discover insecticidal soap to be a very inexpensive and safe way to rid your houseplants of pests.


Warning:  Insecticidal soaps, like other soaps and detergents, may irritate skin and eyes. When they are swallowed, they may cause vomiting and gastric distress. Avoid direct contact.

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