japanese red maple - Knowledgebase Question

Brick, Ne
Avatar for slclay
Question by slclay
June 30, 2010
Just noticed that the tree has a large amount of cottony white mostly underneath the leaves and branches, it seems sticky.

Answer from NGA
June 30, 2010
That sounds like a scale insect. 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. I'd monitor the situation to see if it clears up without spraying.

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