What's eating my quercus coccinea?

Scarlet oak faces oak leaf roller caterpillars, gall wasps, scale insects, and oak aphids outdoors. Squirrels take acorns; deer browse young saplings. The greatest recurring threat is gypsy moth / spongy moth caterpillars, which can fully defoliate a tree in a bad outbreak year.

Mass defoliation of branches in late spring; repeated defoliation weakens and can kill mature trees Apply Bacillus thuringiensis var. kurstaki (Btk) spray to foliage while caterpillars are small; use sticky band traps around trunk; remove egg masses in winter

Sticky honeydew on leaves, sooty mould, curled or yellowed new growth in spring Blast colonies off with a strong hose jet; encourage ladybirds and lacewings; insecticidal soap spray as a last resort

Distinctive marble, spangle, or knopper galls on leaves, stems, or acorns — rarely life-threatening but heavy infestations reduce acorn crop No treatment needed for established trees; remove heavily galled acorns to limit the next generation; maintain tree vigour

Strip acorns entirely; gnaw bark on young branches causing dieback Protect young trees with spiral guards or wire mesh around the trunk; no practical control on large trees