Hazel leaf gall midge

The Hazel leaf gall midge (Mikomyia coryli) is a small dipteran insect belonging to the family Cecidomyiidae. This specialist pest is known for causing characteristic leaf galls on plants of the Corylus genus, impacting the physiological health of the host.

The primary hosts of this species include hazel (Corylus avellana) and various cultivated hazelnut varieties. It is considered a minor but persistent pest, primarily affecting young nurseries and orchards where extensive damage can hamper the vegetative growth of young trees.

The biology of Mikomyia coryli is synchronized with the growth of its host. Adult midges emerge in the spring, coinciding with leaf bud break. Females deposit eggs onto young leaves. As larvae emerge and begin feeding, they induce gall formation, which provides both nutrition and shelter for the larvae throughout their development.

Visual symptoms of infestation are distinct, presenting as small, numerous, and often reddish or greenish protrusions (galls) on the leaf blades. Significant infestation can lead to leaf curling, chlorosis, and premature senescence, which reduces the tree's photosynthetic capacity and potential nut yield.

To manage Mikomyia coryli effectively, growers should employ an integrated pest management (IPM) approach. Key strategies include:

• Monitoring foliage during the early spring growth period.
• Sanitation practices such as removing and destroying infested leaves to reduce the overwintering population.
• Applying systemic insecticides when adult activity is observed before the larvae are fully enclosed in the galls.