Insecticidal Soap Spray

Organic insecticides use naturally occurring substances to kill insects, or they use simple chemicals that break down without harming the environment. I really don't like to use insecticides of any kind, but sometimes they can help. 

Pests in the organic garden are expected - it's just part of the process. It's pretty remarkable how a healthy plant can resist and recover from an attack from pests. I had read about how healthy plants can do this in the literature, and it didn't seem plausible to me, but I've actually seen it in my own garden. If a plant is already weakened by disease, poor growing environment, or injury, it's much more likely to succumb to an insect attack. 

The first step to controlling pests, then, is to grow the strongest, healthiest plants you can. 

But still, we are growing our vegetables to reap a harvest for ourselves, not just feed the local wildlife! It's perfectly OK to protect your garden.

Insecticidal Soap Spray 

A soap spray is a great insecticide - it's cheap, easy to make, and easy to use. As I was checking my sources for this article, I found all kinds of homemade insecticide sprays including soap and oil, soap and water (no alcohol), and a solution made from tomato plant leaves. 

Here's how to make a simple soap spray yourself: 

  • Mix one part water and one part isopropyl alcohol in a spray bottle
    • For example 1 cup of water and 1 cup of isopropyl alcohol
  • Add a small squirt of liquid soap, preferably an environmentally-friendly brand
    • Dr. Bronner's Castile soap is a good choice.
    • Or, use a basic dish soap without added bleach or degreaser. 
  • Spray on the insects themselves on the plant. 

It works only if it touches the insect itself. The soap makes the spray stick to their bodies and it also breaks down some of their tissue cells. This allows the soap and the alcohol to dry out the insect and kill them. You have to spray thoroughly to coat as many of the pests as possible. 

Don't forget the undersides of leaves. Insects love to hide under the leaves

Manufacturers sell premade insecticidal soap sprays which work in the same way. 


How to Use Insecticidal Soap Spray

Soap spray works primarily on soft body insects such as aphids, mealybugs, thrips and spider mites. I've used it successfully to control young squash bugs, too, before they develop their exoskeleton.

The drawback with soap spray is that it is temporary. Once it dries it is ineffective, which means you have to spray every few days. If you have a community garden plot and you only visit the garden once or twice a week, it can be difficult to control the insects with this method. 

Additionally, spraying soap spray can get tedious in a large garden. You can use a pressurized sprayer (also called a garden sprayer) to make the job a bit easier, but that will only scale up so much. 



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