Wrong Insecticidal Soap Spray Concentration Can Damage Plants

Dr Bonners peppermint soap

Q. Is there a certain kind of soap spray that is best for plants? I remember you telling us at the grape seminar that if our leaves were being eaten that we should use a diluted soap spray on them.  I did that last year with success.  This year I tried it on a few different plants and the leaves did not like it AT ALL?  I think I used a soap that is more natural eco friendly (Costco brand) so I don't know if there is something in it that they don't like?  Is my concentration off?  The leaves of everything I sprayed ended up with brown spots.  Doesn't seem to have done too much damage over all, everything is still growing and got new growth shortly after, but those originally sprayed leaves never recovered.  THANKS

A. I'm sorry you had some bad luck with soap spray. It is very important that you not use very much of this soap when mixed with water. 1 teaspoon in a gallon of water is usually enough. Here are some basic guidelines to follow:

Safers insecticidal soap

•           if you are not sure about the soap you are using and whether it is safe or not, use commercially prepared insecticidal soaps

•           insecticidal soaps kill by coming in contact with the insect. They leave no residue on the plants that will kill the insects.

•           Repeated sprays on some plants may cause damage to the plants

•           use the purest water possible such as distilled water rather than Water

•           fog-like sprays are more effective than large droplets

•           spray in the evening or early morning hours

•           insecticidal soaps may cause a burn on the leaves of sensitive plants such as the cole crops like broccoli, cauliflower, cabbage and kale

•           a good rate to use it as a 2% solution so mix no more than 2 ounces in 100 ounces of water

•           if using your own soap such as Ivory liquid don't use anything with extra ingredients such as hand conditioners or special aromas like lemon scented

•           insecticidal soaps worked best against insects with soft bodies like aphids, thrips, whiteflies, spider mites, and a young leafhoppers.

•           Don't expect a 100% kill. Insecticidal soaps may only kill half of the insects. Repeat sprays will be needed as the plant grows larger

I hope this helps.