Blue underwing

The Blue underwing (Catocala fraxini) is a large moth species belonging to the order Lepidoptera and the family Erebidae. Recognized as one of the largest moths in the genus, it is widely distributed across temperate regions of Europe and Asia, often living in deciduous woodlands and riverine forests.

This species is primarily associated with trees of the Salicaceae family. The larvae (caterpillars) feed extensively on the foliage of Populus (poplar), Salix (willow), and occasionally Betula (birch) and Alnus (alder). While typically not considered a major agricultural pest, they can cause localized outbreaks that impact tree health.

The life cycle involves a single generation per year (univoltine). The insect overwinters in the egg stage, which is deposited in the crevices of the bark. Caterpillars emerge in spring and undergo a feeding phase characterized by nocturnal activity, while resting during the day. Pupation occurs in summer, usually within a cocoon tucked between folded leaves.

The damage caused by the larvae is categorized as defoliation. High larval densities can strip trees of a significant portion of their leaf area, which hinders tree growth, weakens the vascular system, and makes the tree more susceptible to secondary pests, such as wood-boring beetles and pathogenic fungi.

Control measures primarily involve monitoring and physical control in smaller gardens, such as manual collection of larvae where feasible. In forest management or large plantations, biological control using microbial agents (such as Bt-based products) is preferred. Chemical insecticides are reserved for severe infestations and should be applied targeting the early larval stages.