Lilac leafminer

Lilac leafminer larvae create pale, blotchy mines within lilac and ash leaf tissue, beginning in late spring and continuing through early summer. The damage appears as irregular, winding tunnels visible on the leaf surface, initially thin lines that expand into larger papery areas as larvae feed and grow. Affected leaves may yellow and drop prematurely if mining is heavy. You identify the problem by the characteristic mining patterns.

Remove and destroy heavily mined leaves during summer to reduce overwintering populations. For valuable specimens, apply horticultural oil in late winter to target pupae and overwintering stages. Once mining damage appears, spinosad or neem oil applied to leaf undersides targets young larvae; repeat every 7 to 10 days. Maintain plant vigor through appropriate cultural care.