Blueberry Stem Gall Wasp (Hemadas nubilipennis)

Kidney-shaped gall on the stem of Blue Ridge Blueberry (Vaccinium pallidum).

This species of wasp is parasitic on blueberry species (Vaccinium sp.). It can become a pest as the formation of galls limits fruit production. Wasps (which are almost all female) emerge from previous galls in spring for mating season. Females pierce the lower surface of the blueberry stems and deposit their eggs there. Additionally, they stab the shoot tips in order to prevent more growth. The plant reacts to the deposition of eggs with the formation of galls. Branches with galls are incapable of producing flowers or fruit. It is recommend that prescribed burns be performed in fall to control any problems.