Blueberry stem gall wasp

Blueberry stem gall wasp

Blueberry stem gall wasp (Hemadas nubilipennis) cause swellings (galls) on canes at egg deposition.

Dormant blueberry bush with several swellings roughly the size and shape of unshelled peanuts. Swellings are maroon in color and are located on twigs off of the main branch at varying heights.

Swellings first appear greenish to red in color. Older galls appear gray and corky and often have exit holes.

Blueberry stem with three lumpy, egg-shaped galls. Two galls are bright red and shiny. One gall is lumpy, dull gray, and has multiple pin-sized holes.
Old and new galls from blueberry stem gall wasp. Older galls have exit holes and grayish color.

Larvae overwinter in galls then emerge as adults in spring.

Cross-section of corky gall showing multiple internal chambers. One chamber has a cream-colored sphere inside of it.
Cross-section of gall with overwintering larva.
Close-up of a curled, translucent larva inside of a frass-lined tunnel. Larva has no discernible limbs or features.
Cynipic gall wasp larva.
Blueberry branch with cluster of blossoms, leaves, and large dark corky mass situated above blossom cluster. A black wasp the size of a pinhead is perched atop the black gall.
Blueberry stem gall wasp perches atop a gall.

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