This species overwinters as eggs, larvae, and adults. Larvae mine garlic mustard leaf stalks, shoot bases, roots, and crowns throughout winter and spring, developing through three instars. Mature larvae exit plants in late spring and pupate in the soil. New adults emerge from late spring through early summer and feed briefly on garlic mustard leaves before aestivating (becoming dormant) throughout the remainder of summer. Adults become active again in late summer/early autumn, feeding on garlic mustard rosette leaves. Oviposition begins in early autumn, continues throughout the winter, and ends in early spring, though egg-laying stops if mean daily temperatures fall below 23°F (–5°C). Females lay eggs in leaves just underneath the epidermis and in leaf petioles by chewing holes and laying single eggs. On average, females lay 230 eggs in their lifetime. There is one generation per year.