Pine web-spinning sawfly

The pine web-spinning sawfly (lat. Acantholyda posticalis) is a significant forest pest belonging to the order Hymenoptera, family Pamphiliidae. This insect is widely recognized for the severe defoliation it causes in Scots pine forests across Europe and Asia, posing a major threat to commercial timber production.

The primary host for this species is the Scots pine (Pinus sylvestris). Although it can affect trees of various ages, it typically targets middle-aged stands. The impact is most severe in dry, sandy soils where trees are already under physiological stress, making them less resistant to mass outbreaks.

The biological cycle is univoltine. Adult sawflies emerge in May or June, depending on local climate conditions. Females deposit eggs individually on the previous year's needles. Upon hatching, the larvae immediately construct silk nests or tubes, which they use for shelter while feeding on the surrounding pine needles.

The damage caused by the larvae results in the loss of foliage. By cutting needles at the base and webbing them together into dense structures, the larvae effectively remove the tree's photosynthetic capacity. Continued infestation over several years leads to stunted growth, canopy thinning, and in many cases, total tree mortality.

Management of Acantholyda posticalis requires an integrated approach. Control measures involve regular scouting to monitor larval populations and egg placement. Chemical intervention is typically performed using registered insecticides during the early larval stages when the individuals are most vulnerable to contact or systemic exposure.