Pest information courtesy of USFS Fact Sheets:
Insects: Leaf stalk borer and petiole-borer enters the leaf stalk
just below the leaf blade and defoliates. Serious injury to a healthy tree is rare.
Gall mites stimulate the formation of growths or
galls on the leaves. The galls are small but can be so
numerous that individual leaves curl up. Galls are not serious, so chemical controls are ususally
Aphids infest maples. High populations can
cause leaf drop. Another sign of heavy aphid
infestation is honey dew on lower leaves and objects
beneath the tree.
Perhaps 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.
Anthracnose can be a problem in rainy
disease causes light brown or tan areas on the leaves.
Girdling roots growing around the base of a maple trunk
rather than growing away from it can choke the trunk.
Girdling roots are detected by examining the base of
the trunk. The lack of trunk flare at ground level is a
symptom and treatment can be as harmful as the problem.
Scorch can occur in maples during periods of high
temperatures with wind. Trees with
poor root systems encourage scorching. Scorch symptoms are light brown or tan dead
areas between leaf veins.
Tar spot and a variety of leaf spots cause some
concern among homeowners but are rarely serious
enough for control.
More on Tree Insects and Disease