Small in size but when large in numbers oyster shell scale insects can wreak havoc on many of our trees and shrubs.
They feed by sucking plant juices from the cells below the bark along the trunk and stems. When populations are high it can cause branches to die and the plants to decline.
Control small infestations with a small plastic pad. Gently rub the scale covered trunks and branches to remove old scale coverings and eggs.
Treat with an eco-friendly product like insecticidal soap or ultra-fine Year-round Spray Oil when the Vanhoutte spirea are in bloom. Make a second application when the Annabelle type hydrangeas’ blossoms change from white to green in milder climates. This is when the immature crawlers are out from under the hard shell and are vulnerable to these chemicals.
Lightweight oils can be used in the summer. They cover and smother the insects.