Chestnut aphid

Systematic position. The chestnut aphid (Myzocallis castanicola) belongs to the order Hemiptera and the family Aphididae. It is a highly specialized insect pest that targets specific host trees, mainly from the genus Castanea and Quercus, acting as a sap-sucking parasite that can significantly affect plant vigor.

Host plants and distribution. This aphid primarily infests the sweet chestnut (Castanea sativa) and various oak species. The insects inhabit the abaxial (underside) surfaces of leaves, which often shields them from initial detection by observers or predators until the infestation becomes significant.

Biology and life cycle. The life cycle involves a complex alternation between parthenogenetic and sexual reproduction. Eggs typically overwinter in bark crevices. Once temperatures rise in spring, the hatching nymphs begin the cycle, producing several generations of wingless and winged forms throughout the growing season to maximize population growth.

Damage and economic impact. Feeding activity results in leaf yellowing, stunting, and premature senescence. Furthermore, the aphids secrete large amounts of honeydew, which promotes the growth of sooty mold. This layer of mold blocks sunlight, hindering the tree's photosynthetic ability and significantly degrading the aesthetic quality of the trees in parks and forests.

Control measures. Management relies on Integrated Pest Management (IPM) practices. This includes the application of systemic insecticides if threshold levels are exceeded, as well as promoting natural biological control agents such as lady beetles, lacewings, and hoverflies. Maintaining tree health through proper fertilization and watering also aids in resilience against attacks.

• Regular monitoring of leaf undersides during the spring.
• Application of targeted systemic insecticides when necessary.
• Conservation of natural predators such as ladybugs.
• Removal of severely infested branches in landscape settings.