Kermes Scale Lifecycle: Tips On Treating Kermes Scale Insect Pests

Kermes Scale Insects On Plant
kermes scale
(Image credit: James Solomon, USDA Forest Service,

What are kermes scale pests? Kermes scale are aggressive, sap-sucking pests that can cause significant damage to oak trees. Treating kermes scale on plants is attained by a variety of methods. Read on to learn about kermes scale control.

Kermes Scale Life Cycle

Pinning down kermes scale life cycle is a difficult task. According to Illinois State University Extension, there are more than 30 different kermes scale species. Identification of the specific species is difficult and hatching times vary widely. Your local Cooperative Extension Agent can advise you on what types of kermes scale are present in your area, and about the best times for treating kermes scale pests on your trees.

Treating Kermes Scale

Kermes scale pests are most likely to infest trees that are under stress. Ensure trees are properly watered and fertilized. Prune infested twigs and branches and keep the area under the tree free of plant debris. Encourage beneficial insects in your garden, as parasitic wasps and ladybugs will help keep kermes scale in check. Use chemical insecticides only when nothing else works, as insecticides aren’t selective and will kill bees and other beneficial insects as well as scale, often resulting in pests that are resistant to chemicals and more difficult to control. Treating kermes scale is most effective when the pests are newly hatched or early in the crawling stage, which is autumn for most species. However, some species may produce crawlers in midsummer. Keep in mind that sprays won’t penetrate scales’ tough, waxy covering. Try using a pyrethroid-based insecticide, which is plant-based and safer for beneficial insects. You can also spray overwintering scales with horticultural oil in late winter or early spring. Dormant oil is effective when temperatures are above freezing. Both oils will smother the pests. Insecticidal soap sprays may be effective on scales that are recently settled and are relatively safe for beneficial insects because the spray is effective only when wet. However, direct contact will kill the good guys. Also, don’t use insecticidal soap spray when temperatures are hot, or when the sun is directly on the foliage.

Mary H. Dyer

A Credentialed Garden Writer, Mary H. Dyer was with Gardening Know How in the very beginning, publishing articles as early as 2007.