Willow-bean Galler

Euura proxima

The red, bean-shaped growths known as 'Kidney Bean galls' that grow on willow leaves are galls formed by sawfly larvae. The adult sawfly lays an egg in the leaf tissue, prompting the plant to produce a protective, nutrient-rich gall for the larva to consume. These galls are frequently found on narrow-leaved willows such as the White Willow (Salix alba). The galls typically intersect the leaf blade but tend to develop more prominently on the upper surface. It is common for multiple galls to be present on a single leaf. The galls appear green, turning reddish on the top.