Japanese Maple problems
There is a white cottony substance on the leaves and branches. Guessing tree is about 15 years old. How do I treat?
It sounds like you have either mealybugs or possibly scales, which are closely related to mealybugs and are an occasional problem on maples. One of the most common is cottony maple scale. The insect forms a cottony mass on the lower sides of branches. Scales are usually controlled with horticultural oil sprays. Neem oil is also effective. Here is more iinformation: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm