Willow leaf beetle

The willow leaf beetle (lat. Gonioctena viminalis) is a member of the Coleoptera order and the Chrysomelidae family. It is recognized as a significant pest specifically targeting Salix species, causing notable damage to willow plantations and ornamental trees.

Physically, the adult beetle is about 5–7 mm long with a distinctive pattern of black spots on a yellowish-brown background. The larvae are also folivores, often seen feeding in groups on the underside of leaves or along the margins, gradually causing extensive damage to the tree's foliage.

The biological cycle consists of one generation per year. Adults hibernate in the soil or leaf litter, emerging in spring to feed on fresh foliage and mate. Female beetles deposit eggs on leaves, and after hatching, the larvae undergo several instars, feeding voraciously before pupating in the soil.

The damage caused by Gonioctena viminalis manifests as partial or complete defoliation. This process significantly affects the tree's vigor, reduces its photosynthetic capacity, and hinders overall growth. Heavy infestations can lead to stunted growth in young willows and increase vulnerability to secondary environmental stressors.

Effective management strategies include both cultural and chemical control measures. It is advisable to monitor tree health during the spring months and remove leaf litter if necessary to reduce overwintering populations. For large-scale protection, applying appropriate contact or systemic insecticides during the peak larval feeding period provides the most effective result.