What's eating my common lilac?

Common Lilac is most plagued by lilac borer, a moth whose larvae tunnel into stems and cause die-back. Oyster shell scale coats branches. Privet leafminer disfigures foliage, and aphids cluster on new growth. In US gardens, deer and rabbits browse young shoots. Lilac borer is the most damaging insect pest.

Larvae tunnel into main stems; sawdust-like frass at entry holes, branch wilt, and eventual die-back. Prune and destroy infested wood. Apply permethrin to trunks in late spring when adult moths are flying. Pheromone traps help monitor timing.

Flat oyster-shaped grey scales encrust stems; heavy infestations cause yellowing, die-back, and bark damage. Scrape off with a soft brush; apply horticultural oil in late winter before bud break to smother overwintering scales.

Colonies on shoot tips distort new growth; honeydew leads to sooty mould on leaves below. Strong water jet; insecticidal soap spray; encourage ladybirds. Avoid excess nitrogen fertiliser that produces soft, aphid-attractive growth.

Deer browse soft shoot tips; rabbits gnaw bark at ground level, potentially ring-barking young plants. Rabbit guards around the base; deer fencing or repellent sprays. Protect bark through winter with wire mesh collars.