The following points recap the highlights of this pest. A cottony maple scale outbreak will not kill the trees. Only silver maples are likely to be heavily infested though other trees may have some scales. Treatment is not advised. Treatment is unnecessary and environmentally disruptive.
ISU advice is to endure the temporary annoyance if possible.
If small trees or trees overhanging decks, etc. MUST be sprayed, wait until early July. Two treatments are necessary. Homeowners are encouraged to spray with insecticidal soap if they decide to spray in spite of the absence of any direct threat to tree health and vigor. Soap or detergent sprays are non-toxic to applicators and people and pets in the yard.