What's eating my korean box?

Korean box (Buxus sinica var. insularis) is fully susceptible to box tree moth — a serious invasive pest — as well as boxwood leafminer and psyllid. Its cold hardiness does not confer insect resistance. In North America where box tree moth is spreading, it should be monitored as carefully as any Buxus species.

Ravenous caterpillars consume leaves and bark, filling the plant with webbing. Complete defoliation in one season is possible; repeated attacks kill plants. Use pheromone traps to monitor. Apply spinosad, pyrethrin, or lambda-cyhalothrin sprays targeting young caterpillars. Repeat every 2–3 weeks during active periods. Remove egg masses and caterpillars by hand where practical.

Blistered, discoloured patches on leaves from larval mining between leaf layers. Heavy infestations cause significant leaf drop and sparse growth. Apply systemic insecticide (imidacloprid) in spring. Clip and destroy infested foliage. Time foliar sprays (bifenthrin, malathion) to adult fly emergence in May–June.

Fine stippling and bronzing of leaves, most noticeable in dry summer conditions. Foliage loses its glossy appearance and looks dull. Apply horticultural oil or a labelled miticide in spring. Overhead irrigation in dry spells discourages mite build-up. Avoid drought stress which makes plants more vulnerable.