Are your trees dripping sap? In past years this condition has been caused by aphids, but this year we have a different pest. The lecanium scale may be the culprit. Scale insects are among the most injurious pests that attack our trees and shrubs. The lecanium scale infests fruit trees, poplars, roses, willows, boxelders, ash and elms.

The scale of the lecanium scale is bowl or dome shaped, slightly longer than wide; smooth and shiny brown in color and about 1/8 to 1/4 inch in diameter. The scale is protective covering of wax, secreted from their body. This makes chemical control very difficult.

The lecanium scale overwinters as partly grown scales on twigs of last season's growth It matures in late spring and lays it's eggs. These eggs will hatch in late June or July. After hatching the young scale "crawlers" move about for a short time, then settle down to feed, sucking sap from the plant. Chemical control will be the most effective during the "crawler" stage. Once they are under their protective scale covering, most controls are quite ineffective. Heavy scale infestations weaken your trees and shrubs and may eventually lead to their death.

Chemical control of the lecanium scale should be attempted about the middle of June and then retreated again 10 days later. A Malathion, Sevin, or Diazinon spray will give adequate control of the pest even though the insecticide won't completely eliminate the problem. 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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