Oak lecanium scale eggs

Oak and European fruit lecanium scale are one of the largest soft scales in our area. Scale

Oak lecanium scale eggs within an ovisac. Photo: SD Frank

Oak lecanium scale eggs within an ovisac. Photo: SD Frank

ovisacs are brown and rounded reaching 6mm in diameter. This is the most noticeable stage and is present right now. As members of the soft scale family Coccidae, lecanium scales produce honeydew that can cause sooty mold on oaks or plants below. Oak lecanium scale primarily infests oaks trees. However, European fruit lecanium can infest many tree species including oaks. They are impossible to tell apart with out a microscope (even then it is hard). Large populations can reduce growth and vitality especially in newly planted trees.

Eggs are present now under adult scale covers and crawlers are beginning to hatch. The crawler stage should be targeted for best efficacy. On trees small enough to treat foliage horticultural oil can be used. On larger trees a systemic such as dinotefuran can be applied as a drench or trunk injection. This scale is not easily eradicated and optimal control measures are still unclear. It is attacked by many parasitoids and predators that can reduce scale abundance if protected from insecticides. A short video by graduate student Emily Meineke describes the scale biology. She is conducting research to understand why lecanium scale outbreaks on urban trees.

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