How to Control Scale Insects

What You'll Need
Garden shears
Insecticidal soap
Predatory beetles
Coreopsis plant
Horticultural oils

Scale insects destroy plants by sucking sap from their tissue, turning their leaves yellow and eventually killing them if left unchecked. One of the more insidious garden pests, scale insects can attack plants year round. In order to properly take care of scale insects, you have to know what you are looking for, what you can plant to discourage them, and how to get rid of them should they already be present in your garden. It’s best to avoid chemical pesticides because the job can be done without them. If you want to control insects using chemicals, there are options available to you, but this project involves companion planting and other organic methods.

Step 1: Identify the Pest 

Make sure you know what scale insects are before you act to get rid of them. They are very small, typically a tenth of an inch in size, of a round or oval shape with no legs. Look on the undersides of leaves, at leaf joints or on the stems to see if they are gathering there. If you see blackened leaves or stems, there’s a good chance your plants have been infected by scale insects.

Step 2: Prune Obviously Infected Areas

With your garden shears, prune off all branches and twigs that have been infected and dispose of them elsewhere.

Step 3: Companion Planting

This step may take a while, and there are things you can do in the meantime, but companion planting will attract predatory insects like certain kinds of beetles and ladybugs that will help devour the scale insects. Planting dill, fennel, salvia and coreopsis near the infected plants will help in the long run.

Step 4: Rinse the Infected Plants

Use a soft cloth or sponge dipped in a mixture of water and insecticidal soap to immediately rid the plants of the scale insects. Afterwards, make sure you rinse the plants of with plenty of water to get the soap off.

Step 5: Release Predators

You can opt to purchase certain species of beetles and/or wasps that feed on scale insects to help with the infestation.

Step 6: Spray Deterrent On the Plants

Mix insecticidal soap with horticultural oils and spray it directly onto the infected plants. This helps to smother the scale insects. You can also spray Pyrethrin, an organic pesticide made from chrysanthemum onto the plants. This should only be done if all else fails.

Scale insects can slowly devour both indoor and outdoor plants. Unless you intervene, these pests will gradually suck the life right out of your garden. There are many methods you can employ to get rid of the pest, from companion planting to spray-on solutions, none of which involve chemicals. You can resort to chemical pesticides, but you should do so only if nothing else works. Always be aware, too, that pesticides can have side effects for other plants.