What's eating my acer rubrum 'october glory'?

Acer rubrum 'October Glory' can be attacked by several pests. Cottony maple scale is the most common, coating branches with white waxy egg masses. Asian longhorned beetles are a serious invasive threat in the Northeast US. Aphids, particularly woolly aphids, cluster on stems, and gall mites cause the distinctive bladder galls on leaves.

Conspicuous white cottony egg masses on stems and branches in late spring; heavy infestations cause yellowing, premature leaf drop, and branch dieback Apply horticultural oil at the crawler stage in early summer; dormant oil in early spring before bud break; parasitic wasps provide good natural control — avoid broad-spectrum insecticides

Numerous small, red or green pustule-like galls on the upper leaf surface in spring; cosmetic but rarely causes lasting harm No treatment is needed for established trees; rake and dispose of fallen leaves; a preventive dormant oil spray can reduce mite populations

White woolly masses on bark and stems; sticky honeydew; ants farming colonies on branches; minor leaf curl on new growth Apply insecticidal soap or horticultural oil; scrub woolly aphid colonies from bark; encourage natural enemies

Round exit holes ~1 cm diameter in bark; sawdust-like frass at the base; dieback progressing from the crown — maples are a preferred host This is a regulated invasive pest in the US and UK — report sightings immediately to your state agriculture department or the USDA APHIS; no home treatment; infested trees are usually removed