Willow sawfly

The willow sawfly (lat. Arge ustulata) is an insect belonging to the order Hymenoptera and the family Argidae. It is a well-known pest that specifically targets deciduous trees, causing significant damage to the aesthetic and biological state of plantations, particularly in forest-steppe and temperate regions.

The primary host plants for this species are various members of the Salicaceae family, most notably willows and poplars. In urban landscapes, the insect is frequently found on ornamental willow cultivars, where the activity of larvae can lead to severe stress for the plants during the growing season.

The life cycle of Arge ustulata involves complete metamorphosis. Adults emerge in spring, and females deposit eggs into the marginal tissues of young leaves. The larvae, often called false caterpillars, pass through several instars while consuming large amounts of foliage, which is their primary source of nutrition until they pupate in the soil.

Damage caused by the larvae is characterized by skeletonization and massive defoliation of the canopy. As they mature, the larvae consume almost the entire leaf blade, leaving only thick veins. This results in reduced photosynthetic capacity, which weakens the tree, inhibits growth, and may lead to branch dieback in cases of recurrent infestation.

Effective management requires a combination of strategies to minimize environmental impact. Preventive measures include monitoring for early larval activity and maintaining tree health through proper irrigation and fertilization. When outbreaks occur, chemical or biological insecticides are applied to treat the foliage and stop the larval feeding cycle.

• Manual removal of egg batches from leaves in early spring.
• Encouraging natural predators such as birds and parasitic wasps.
• Application of bacterial-based bio-insecticides targeting young larvae.
• Systemic insecticide treatments during high-density infestations.