Purple willow gall midge

Systematic position. The purple willow gall midge (Rabdophaga purpureaperda) belongs to the order Diptera, family Cecidomyiidae. This insect is a specialized pest that specifically targets willow species, causing significant structural changes in plant tissues.

Host plants. The primary hosts include various Salix species, particularly the purple willow (Salix purpurea). It is a major concern in commercial osier willow plantations and decorative nurseries where shoot quality is essential.

Biology and life cycle. The adult midges emerge in spring to lay eggs on the bark of young, developing shoots. Upon hatching, the larvae bore into the tissue to feed, inducing the plant to create gall structures. The midge typically completes one generation per year, overwintering as larvae within the infested plant parts or soil.

Damage and economic impact. The infestation leads to the formation of galls, causing localized swelling and distortion of the shoots. This damage impairs nutrient transport, weakens the structure of the willow stems, and renders them unsuitable for basketry or artisanal weaving, significantly reducing the economic value of the harvest.

Control measures. Effective management includes cultural practices such as pruning and destroying galled shoots before the emergence of the next generation of adults. In severe cases, targeted applications of systemic insecticides during the peak flight period can help manage population levels and protect willow plantations.