Elm zigzag sawfly

The elm zigzag sawfly (Aproceros leucopoda) is a destructive insect species belonging to the order Hymenoptera and the family Argidae. Originating from East Asia, this invasive pest has spread rapidly across many European countries, becoming a significant threat to various elm tree species (Ulmus species).

The life cycle of Aproceros leucopoda is notably rapid, with the species capable of producing up to four generations per year depending on the climate. Adults are generally small, dark-colored wasps, while the larvae are the primary cause of damage, actively consuming the foliage of host trees throughout the vegetative season.

The feeding behavior of the larvae is highly diagnostic. They consume leaf tissue in a distinct zigzag pattern, which eventually expands to skeletonizing the entire leaf, leaving only the primary veins. This process significantly reduces the photosynthetic capacity of the elm tree, leading to severe defoliation.

Continuous damage from the elm zigzag sawfly can cause long-term physiological stress to the trees. Repeated yearly defoliation weakens the host, making it susceptible to secondary pests and drought. In urban forestry, this pest is of particular concern due to its impact on the health and aesthetic value of street and park trees.

Management and control strategies against this pest involve:

• Regular monitoring of elm canopies for early signs of zigzag feeding patterns.
• Application of selective insecticides targeted at young larval stages to minimize impact on non-target organisms.
• Biological control options, including the use of entomopathogenic fungi or bacteria.
• Promoting biodiversity in green spaces to encourage natural predators and parasitoids.