An online resource based on the award-winning nature guide – maryholland505@gmail.com

Blueberry Stem Gall

12-20-12  blueberry stem gall IMG_7405If you happen to notice a ¾” to 1 ¼”- long, brown kidney-bean-shaped or round structure on a blueberry bush this time of year, you’ve come upon the blueberry stem gall – a summer and winter home for a dozen or so wasp larvae that will pupate and emerge in the spring as very small (less than 1/8”) black wasps (Hemadas nubilipennis). Last summer a female wasp laid her eggs in a tender, developing blueberry shoot. She then climbed to the tip of the shoot and stabbed it repeatedly, causing considerable damage. Within two weeks the eggs hatched, and the larvae began feeding, which, along with the egg-laying, stimulated the formation of the gall. Initially a blueberry stem gall is green and spongy; by fall it turns red, and by late autumn, it is brown and woody. Next summer, look for multiple holes in these galls that were chewed by the exiting wasps.

4 responses

  1. Very interesting.
    How harmful are they to the blueberry plant?

    December 21, 2012 at 1:06 am

    • Apparently they can, but don’t always, damage the fruit.

      December 21, 2012 at 1:17 am

  2. charles astbury

    should not the b berrystem be cut off below the eggs? ..like the rasberry tip.

    December 21, 2012 at 9:22 pm

    • That sounds like a logical step to take, if you don’t wish to share the berries with the wasps!

      December 22, 2012 at 3:10 pm

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