Lecanium Scales Full of Eggs

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Oak lecanium scales and eggs on willow oak. Photo: SD Frank

Oak lecanium scales and eggs on willow oak. Photo: SD Frank

Oak lecanium scale and European fruit lecanium are nearly identical soft scales that infest oaks and many other tree species including redbud, dogwood, maple, fruit trees, and others. In spring adults swell to large (for scales) hemispherical egg cases with thousands of eggs. This is the stage you will see now on infested twigs. The eggs will hatch in a couple weeks and nymphs will crawl out to branches to feed all summer. Egg hatch is a good time to target scales with low toxicity products like horticultural oil and insecticidal soap. We have also had success reducing the abundance of nymphs during summer with horticultural oil. Other products such as systemic neonicotinoids and insect growth regulators are also available for scale management. Trees surrounded by impervious surfaces are most susceptible to scales due to water stress and high temperatures.