Kermes Scale/Drippy Blight

Kermes scale is a commonly seen scale insect on pin and red oak trees. It is associated with a bacteria that is sometimes seen as a sticky substance that collects around the feeding zone of scales.

Identification

Twig dieback on oak trees is a good indicator that the scale and bacteria are present. Look at the base of leaf stems for globular scales. A clear, sticky substance may be visible near the scale feeding sites.

Life Cycle

Small nymphs overwinter near the base of buds. When spring arrives, individuals move to new growth and feed for several weeks before mating and swelling with eggs to large, globular scales about half a centimeter in diameter. The eggs hatch in late summer- early fall and small crawlers locate overwintering sites. There is one generation per year.

Damage

The combination of the pest and the disease causes twig dieback. Prolonged infestations can be detrimental to tree health and eventually lead to death.

Management

The best management of drippy blight is to limit the number of scales present. It is thought that bacteria somehow enter the wounds associated with scales, though this is not yet documented or fully understood.

There are a few different insecticide treatments available for managing kermes scale. A systemic insecticide, dinotefuran, has been effective at times. Also, a spray of an insect growth regulator (pyriproxyfen) targeting the small crawlers can be effective at killing scales.