Club-shaped Poplar Gall

Pemphigus populi

The aphid Pemphigus populi is responsible for the formation of greenish-yellow globular galls on the mid-rib of Black Poplar leaves, close to the base of the leaf. As they age, the galls take on a club shape. Fundatrices, which are females that emerge from overwintering fertilized eggs, induce the galls to create a habitat for their offspring to grow.