The Q&A Archives: Cottony Maple Scale?

Question: I have noticed many white, cottony

Answer: Normally, this scale is a mere curiosity and nuisance. The white egg sacs easily attract attention and the developing scales produce honeydew. Honeydew is the excess water and sugar excreted by many plant sap-feeding insects. Honeydew is commonly mistaken for "plant sap" being dropped on cars, sidewalks and lawn furniture lying under trees. When honeydew collects on leaves and branches, bees, wasps and ants are attracted to the area. If the honeydew is allowed to remain, molds called "sooty fungus" grow on the material, turning the surface a gray-black color.

This pest has numerous parasites and predators that normally keep its populations in check so you may not have to do anything. Like most scale insects, the nearly mature insects, the adults and the eggs are resistant to pesticides, so control needs to be correctly timed and applied when the scales are most vulnerable. This is typically when they are newly forming. Several insecticides are registered for control of scale crawlers and newly settled crawlers. These pesticides, again, often need to be applied in sufficient spray quantity to wet both the leaf upper and lower surfaces. Apply registered products in mid-July and again in the second week of August for best control.

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