Does your cotoneaster hedge have dead or declining areas? This condition may be caused by oystershell scales. Heavy infestations of these piercing-sucking scales greatly reduces plant vigor and often kill the cotoneaster if no control measures are initiated.

The oystershell scale covering is a shiny brownish-gray in color and shaped some-what like an oystershell. The covering of the female is nearly 1/8 inch long, narrow at the anterior end and widened at the rounded posterior end. The covering of the males is smaller and oval-shaped. The eggs over winter beneath the scale of the female insect. When spring is well advanced, the eggs hatch, the tiny insects crawl out and begin sucking sap within a few hours. Within a short period of time the insects form a scale over their body. Control should be accomplished before this scale has been formed.

Tiny insects can be controlled with Malathion, Diazinon, Sevin, Isotox or Orthene. The spray should be applied about May 20-25 or when the lilacs come into bloom and again 10 days later. Other insecticides labeled for scales such as Tempo can also be used. The active ingredient in Tempo is available in Bayer Advanced Garden Multi-Insect Killer.  When using insecticide, mix and apply according to label directions.

This page was last updated April 2003

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