Elm zigzag sawfly

The elm zigzag sawfly (Aproceros umbricola) is an invasive insect species belonging to the order Hymenoptera and the family Argidae. Native to East Asia, it has rapidly spread across Europe, becoming a major threat to elm trees (Ulmus species) in both forestry and urban landscape settings.

The host range of this pest is primarily restricted to elms. The adult females lay eggs into the leaf tissues, and the emerging larvae begin feeding immediately. Due to its high reproductive capacity and lack of natural predators in invaded regions, the population can grow exponentially within a single growing season.

Biological development involves multiple generations per year. The species is largely parthenogenetic, meaning females do not require males to reproduce. This reproductive strategy allows the sawfly to colonize new trees and expand its territory efficiently, often reaching high infestation densities.

The damage caused by the larvae is distinct and easily identifiable in the field. Young larvae create a signature zigzag pattern while feeding on the leaves, while older larvae eventually consume the entire leaf lamina, leaving only the primary veins. Severe infestations lead to significant defoliation and tree stress.

Management and control strategies focus on minimizing population impact:

• Implementing rigorous monitoring to detect early signs of infestation.
• Collecting and destroying fallen leaves to eliminate overwintering cocoons.
• Applying biological insecticides targeting early larval stages.
• Promoting biodiversity in green spaces to support natural parasitoids that prey on larvae.