Disease on Bark of Acers

Question

White cotton wool-like small scales presenting on bark of our acers. Please advise of causes if pest and best treatments.

Answer 1

This could be Mealybug, Wooly Aphid or a fungus.
Also sometime lichen can have a white appearance. Lichen is harmless to the tree.
I would treat with Neem Oil. It works as both an insecticide and fungicide so that you are treating both possible problems.

Here are some links for you.

https://www.gardeningknowhow.com/plant-problems/pests/insects/woolly-aphid-control.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/mealybugs-control.htm
https://www.gardeningknowhow.com/ornamental/trees/maple/maple-tree-bark-disease.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm