Q: I have what I think is a fungus on the underside of my red maple. It looks like white puffs of rice with a black spot on one side of the puff. The fungus is on almost every leaf. Some of the leaves look like they are being eaten by the fungus.
A: It’s not a fungus. It’s cottony maple leaf scale. Most scale insects have hard coatings of wax on their bodies but cottony scale covers itself with fluffy filaments.
As with all scale, control is difficult and timing is key.
I prefer using horticultural oil for control since it is less likely to kill beneficial insects that prey on this scale. Be sure to read the product label for instructions on when and how it can be used. Plan to spend several minutes spraying to assure that you get thorough coverage of the undersides of leaves.