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Monarthropalpus flavus

Boxwood leafminer

Description

Monarthropalpus flavus, commonly known as the boxwood leafminer, is a small fly that affects boxwood species. It primarily targets Buxus sempervirens, Buxus microphylla, and Buxus harlandii, attacking most cultivars. This pest is widely distributed across Europe (prefers warmer areas) and the United States, where it entered with imported boxwood species in the early 1900s. The insect overwinters as larvae inside the leaves, becoming active in spring. After pupation, adults emerge by mid-May, resembling tiny, yellow-orange gnats about 2-3 mm long. Females lay eggs on the upper leaf surface, and larvae hatch to mine the leaves throughout the summer. There is one generation per year. Continuous infestations can cause severe damage, leading to yellowed leaves, premature leaf drop, and weakened plants susceptible to stress or disease.