What's eating my acer rubrum?

Acer rubrum (red maple) is attacked by aphids and cottony maple scale, which encrust branches and produce honeydew. Forest tent caterpillars defoliate trees during outbreaks. Asian longhorned beetle (ALB) is a serious threat in affected US regions. For most gardeners, aphids and scale are the practical everyday concerns.

White fluffy egg masses on branches in late spring; heavy infestations weaken and distort limbs Apply horticultural oil in late winter; systemic insecticide in early summer when crawlers are active

Dense colonies on young shoots and undersides of leaves; honeydew causes sooty mould below Encourage natural predators; use insecticidal soap or neem oil for localized infestations on young trees

Mass defoliation in outbreak years; silk mats on trunks; repeated defoliation weakens the tree Apply Bacillus thuringiensis (Bt) to foliage when caterpillars are small; healthy trees recover from a single defoliation

Round exit holes in bark; sawdust frass at base; larval tunnelling kills limbs — notifiable pest in US and UK Report sightings to USDA APHIS (US) or DEFRA (UK) immediately; no home treatment — official eradication programme applies