Alder leaf beetle

Systematic position. The Alder leaf beetle (Agelastica alni) belongs to the order Coleoptera and the family Chrysomelidae. It is a well-known oligophagous insect that specializes in feeding on specific deciduous trees, often causing noticeable defoliation in forests, riparian zones, and garden landscapes.

Affected crops. The primary hosts for both adults and larvae are Alnus species (black and grey alder). During outbreak years, the beetles exhibit wider dietary habits and may attack other tree species, including hazel (Corylus), hornbeam (Carpinus), willow (Salix), and occasionally fruit trees, leading to agricultural complications.

Biology and life cycle. The adult beetles overwinter in the leaf litter, under bark, or in the topsoil. In the spring, they emerge, feed, and mate. Females deposit eggs in clusters on the undersides of leaves. The larvae go through several developmental instars, feeding voraciously, before descending to the soil to pupate. The species typically produces one generation per year.

Damage patterns and economic importance. Adults create characteristic irregular holes in the foliage. Larvae are even more destructive; early stages skeletonize the leaves, while older larvae consume entire leaf blades, leaving only the midribs intact. Severe infestations can cause premature leaf drop and significantly decrease the vitality and growth increment of the affected trees.

Control measures. Management strategies rely on cultural practices and targeted chemical treatments. Sanitation is critical, such as removing and destroying leaf litter where adults hibernate. When significant damage occurs, contact or systemic insecticides should be applied during the early larval stage. Biological control using pathogens or predator conservation can also suppress population surges.

• Removal of infested leaf litter
• Application of specialized insecticides
• Monitoring of larval activity