Pine web-spinning sawfly

Systematic position: Acantholyda zappei belongs to the order Hymenoptera and the family Pamphiliidae, commonly known as the web-spinning sawflies. These insects are specialized defoliators of coniferous trees, characterized by their unique ability to construct silk-based shelters during their larval stages.

Host plants: This species primarily infests Pinus sylvestris (Scots pine). It shows a preference for middle-aged and mature forest stands, though it can become a serious problem in plantations that are stressed due to drought, poor soil quality, or ecological imbalance.

Biology and life cycle: The species typically completes one generation per year. Adults emerge in spring to mate and lay eggs on the needles. Upon hatching, larvae form communal web nests. These structures provide protection against environmental factors and predators. Larval development concludes in late summer, followed by pupation in the soil, where the insects remain until the next spring.

Damage and impact: Larvae consume pine needles within their silken nests, leading to significant defoliation. A heavy infestation can cause severe crown thinning, resulting in reduced radial growth. Sustained damage over multiple years drastically weakens trees, often leading to mortality or secondary attacks by bark beetles.

Control measures: Integrated Pest Management (IPM) is essential for controlling Acantholyda zappei. This includes silvicultural practices to promote stand health and the protection of natural predators, such as parasitic wasps. When outbreaks occur, the use of selective bio-insecticides targeting young larvae is recommended to minimize environmental impact while effectively managing the population density.