Fenusa dohrnii

Sawfly Fenusa dohrnii

Description

Fenusa dohrnii is a species of sawfly that commonly infests alder trees. It belongs to the family Tenthredinidae. The adult sawflies are small insects, typically measuring around 5 to 7 millimeters in length. They have a black body with yellow or orange markings. The larvae of Fenusa dohrnii are greenish-yellow in color and reach a length of approximately 7 to 9 millimeters. The larvae feed on the leaves of alder trees, causing characteristic damage. They create small notches between two leaves veins and lives inside of the epidermis. The infestation of Fenusa dohrnii can weaken the affected alder trees, particularly if the population is high. Severe defoliation can occur, impacting the tree\'s overall health, growth and aesthetic value (if trees are planted in parks and gardens). Fenusa dohrnii infestation cen be sometimes confused with infestation caused by Heterarthrus vagans. The feeding activity of Heterarthrus vagans larvae results in irregularly shaped areas of defoliation on the leaves. Ussualy only single larva lives on a leaf. In case of Fenusa dohrnii patches are smaller, more regular and more larvae can occur on the leaf.