What is going on with this blackberry shoot?
Exterior structure of the gall.
Rob Last, ©2025, Clemson Extension
This is the gall of a blackberry gall midge. A client recently brought in a blackberry stem, which was swollen and distorted, appearing to be a gall on the stem. Notice how the gall has an overlarge blackberry-type appearance. The shoot tip and blossoms are beginning to die off. The adult blackberry gall midge is a tiny, delicate fly, typically less than 1/8 of an inch, so it is easily overlooked. The adult female fly lays eggs on the stem of the blackberry close to the buds or on wound sites. As the larvae hatch, they burrow into the stem, triggering the plant to release growth hormones, forming the gall. The larvae tunnel in the swollen gall feeding until they re-emerge as adults. The larvae are white maggots (headless and legless and can sometimes be found inside the feeding chambers. Management options typically include pruning out and disposing of the galled shoot.
For more information on growing blackberries, see HGIC 1400, Blackberry and HGIC Blog Blackberries.
Interior structure of the gall.
Rob Last, ©2025, Clemson Extension
