Dasineura fraxini

Ash leaf gall midge

Description

The Dasineura fraxini, commonly known as the ash leaf gall midge, is a species of gall midge that induces characteristic galls on ash trees (Fraxinus spp.), including Fraxinus excelsior, F. angustifolia, F. ornus, and F. oxycarpa. This species is widespread across Europe, commonly found in forests, parks, and gardens. It typically has one generation per year (univoltine) in northern regions and two generations (bivoltine) in southern areas. Larvae develop inside galls on the leaves, overwintering as pupae in the soil and emerging as adults in spring.

The galls form on the underside of leaves along the main veins, appearing as narrow green pouches that house orange larvae. Slit-like openings can be observed on the upper surface of the leaf. High infestation levels may lead to leaf deformation, reducing their aesthetic value and photosynthetic capacity. However, healthy trees usually endure the damage without long-term impact.

Symptom

Narrow green galls measuring 5–30 mm form on the underside of leaves, containing orange larvae. Slit-like openings are visible on the upper surface. Severely infested leaves may become deformed.

Tree Species: Ash

Part of a plant- attacked: Leaf / Needle

Pest significance: Less harmful

Pest Category: Insects

Invasive Species: No

Present in EU: Yes