Willow gall midge Justini

The willow gall midge (Rabdophaga justini) belongs to the order Diptera and the family Cecidomyiidae. This insect is a specialized pest that targets willow species, creating unique morphological changes in the host plant's structure known as galls.

The primary host plants are various species within the Salix genus. The pest specifically selects young, vigorous shoots to deposit its eggs, which leads to the formation of galls that interfere with the plant's normal vascular development and shoot growth.

The biological cycle involves a complex interaction between the insect and the host plant. Upon hatching, larvae stimulate the formation of a gall, which serves as both their nutrient source and physical refuge. Within this structure, the larvae complete their development before eventually emerging as adults to repeat the cycle.

The infestation is characterized by swollen, deformed areas on the willow stems. These galls weaken the integrity of the branches, stunt shoot elongation, and can cause significant dieback. In commercial willow cultivation and ornamental settings, this damage reduces tree health and aesthetic value.

Management and protection strategies require an integrated approach:

• Sanitary pruning: systematically cutting and destroying galled branches before adult midges emerge.
• Chemical control: applying systemic insecticides during the peak activity of adult egg-laying or larval emergence.
• Cultural practices: ensuring adequate plant nutrition and water to mitigate the stress caused by infestation.
• Quarantine: inspecting new nursery stock to prevent the spread of the midge into uninfected areas.