Birch sawfly Arge pectoralis

Taxonomic position. The birch sawfly Arge pectoralis belongs to the order Hymenoptera and the family Argidae. This insect is a specialized pest primarily attacking trees within the Betula genus, making it a significant concern for both silviculture and landscape management.

Host plants and damage potential. The pest specifically targets birch species. Damage is caused by the larvae, which feed on the foliage. Under conditions of high population density, these insects can cause extensive defoliation, which stresses the trees and leaves them susceptible to secondary pathogens and environmental stressors.

Biology and life cycle. Arge pectoralis undergoes a complete metamorphosis. Adult females deposit eggs into the leaf tissue, often creating visible oviposition scars. Upon hatching, larvae feed gregariously on the foliage. Once they reach maturity, they descend to the soil to form cocoons, where they overwinter in a prepupal stage before emerging as adults the following season.

Symptoms of infestation. The primary symptoms of infestation are irregular holes in the leaves, progressing toward complete skeletonization of the leaf blades. In cases of severe infestations, the canopy can be significantly thinned, leading to stunted growth and, in rare instances of repeated defoliation, the death of weakened host trees.

Control measures. Effective management of the birch sawfly requires a combination of monitoring and intervention techniques:

• Conducting periodic surveys of birch stands during the spring and early summer.
• Promoting natural predation by encouraging the presence of birds and beneficial parasitoids.
• Applying biological insecticides containing bacterial agents such as Bacillus thuringiensis.
• Utilizing conventional chemical insecticides for nursery stock or high-value urban ornamental trees.
• Removing debris and lightly cultivating the soil under infested trees to disrupt the pupation cycle of the sawfly.