The leek moth (Acrolepiopsis assectella) goes through eight stages, namely egg, five larval stages, a pupa and the adult moth. The eggs are small, white and elliptical and are laid singly on the leaf of Allium plants. After a wandering period on the leaves, first instar larvae penetrate into the green leaves where they bore galleries. Third, fourth and fifth instars bore into the central yellow leaves of the leek and produce the most severe damage.
First instar larvae are ca 1 mm long, but mature larvae are ca 10 mm with a brown head capsule and . a yellowish-white body. Pupation takes place in a 10-mm-long, cream-coloured, silk cocoon made of characteristic meshes spun on the surface of the leaves or on the flower-stalk of the host plant. The pupa is 7-8 mm long, its colour varies from light yellow in the beginning to brown before adult emergence.
Male and female moth are 8-9 mm long, with a wing span of 15-16 mm. Their general colour is grey-brown with a typical white triangle in the middle of the posterior edge of the forewings. The hindwings are uniformly grey. The moth are active at night and rest during the day.
Development time is temperature dependent. At 25°C, eggs hatch after 3-4 days. Larval development takes 2 weeks, pupal development 1 week and adults can survive 7-10 days. The moths overwinter as diapausing adults.