Answer: Sounds like cottony maple scale. Summer control of scale insects needs to be targeted at the crawlers (immature stage) that usually hatch from eggs in late June through July. The crawlers do not move very far from their hatching site.
The egg hatch occurs for a short period of time, so timing is crucial for effective control. To monitor for crawlers, place a white piece of paper underneath the branch and vigorously tap the branch to dislodge crawlers onto the paper, or wrap the branches with a wide, double-sided sticky tape near the active insects. Inspect the tape often for crawlers. Once the crawlers settle and insert their coiled mouthparts into the plant, which usually takes one to three days, it will be difficult to dislodge them.
Summer sprays of insecticidal soap or conventional insecticides with the active ingredient imidacloprid should control the pests. Some of the trade names are Merit and Bayer Advanced Tree and Shrub.
Best wishes with your maple trees.
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