Fels-Naptha Insecticidal Soap

Before we could jump in the car and run to the garden center for a ready-to-use bottle of insect spray, creative gardeners made their own recipe using Fels-Naptha.  Home made concoctions fell by the wayside as quicker, more convenient methods of pest control became readily available.  The trend toward a more organic lifestyle and a less chemical intensive garden is growing, so insecticidal soap sprays are making a comeback… yea!!!

Fels-Naptha Laundry Bar

Soap is one of the oldest contact insecticides used in dealing with certain piercing, sucking insects.   They are not effective however, on chewing insects such as caterpillars and beetles.  Sometimes you don’t notice the bugs but symptoms of an attack  are a clear sticky substance (honey-dew) or black sooty mold  appear on the foliage.

How it works:  Insecticidal soap works only on direct contact by penetrating the insects’ cuticles, which causes cell collapse and dessication. In other words, it dries them out.  If the insect has not been coated with the spray, it will not be affected by walking over or ingesting plant material that has been treated.

Critters to target:  Target soft-bodied pests such as aphids, adelgids, lace bugs, leafhoppers, mealy bugs, thrips, sawfly larvae, spider mites and whiteflies.  To varying degrees, soap sprays are also effective against chiggers, earwigs, fleas, mites, scales, and thrips.

When to spray:  Insecticidal soap should be applied when conditions favor slow drying to maximize effectiveness, e.g., in the early morning hours with dew coverage or in the early evening. Avoid treating with soaps on hot sunny afternoons which promote rapid drying of the material. Thorough coverage is vital for the soap to be effective. Spray the upper leaf surface as well as the underside of foliage thoroughly, but not beyond the point of runoff.  Take a walk about a couple of days after spraying to check the treated plants.  You may need to treat again.

Side Effects:

Insecticidal Soap Can Burn Plants: Insecticidal soaps may cause phytotoxicity (toxic to the plant) symptoms, such as yellow or brown spotting on the leaves, burned tips or leaf scorch on certain plants.  Spot treat a part of the plant and wait at least 24 hours to see if any phytotoxic symptoms develop before treating an entire plant. Plants under drought stress, young transplants, un-rooted cuttings and plants with soft young growth are more likely to develop phytotoxic symptoms and should not be treated with soap.

Beneficial Insects:  Soap has a limited effect on non-target beneficial insects such as ladybird beetle larvae, parasitic wasps and honey bees, but it can be quite disruptive to soft-bodied predators, such as syrphid fly larvae and beneficial predatory mites. Once the spray has dried, however, beneficial insects can safely re-enter the treated area.

Insecticidal Soap Concentrate

  • ¼ bar Fels-Naptha Laundry Soap, grated
  • 1 quart very hot water

Stir the grated soap into the hot water until dissolved. Store this insecticidal soap concentrate in a labeled covered jar.

Insecticidal Soap Spray – mix 1 teaspoon of the concentrate with 1 quart of water and pour into a sprayer. Make sure you label that spray bottle!

You may have to scout the laundry detergent aisle to find Fels -Naptha.  Publix carries it and it’s usually on the top shelf.  If you still can’t find it, forget asking any clerks younger than 50.  Chances are they wont know what you’re talking about.   Go online or look for brands like Ivory Snow, Ivory Liquid, Dr. Bronner’s, or Shaklee’s Basic H. Clear dishwashing detergents are not the same as soaps and should not be used in soap sprays and don’t use any product with additives like fragrance.

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One Response to Fels-Naptha Insecticidal Soap

  1. Mary Hammond says:

    I recently bought a bar of Fels Naptha soap at WalMart in the laundry aisle for less than $1.


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