Wednesday, August 26, 2009

Bedeguar Galls




The strange object in the upper image, looking like an alien visitor from outer space, is a young bedeguar gall caused by the gall wasp Diplolepis rosae, which lays its eggs in the dog rose host and triggers this proliferation of tissue. When fully grown, like the example in the bottom image, the core of the gall contains up to 60 chambers, each with a wasp grub inside and enclosed in a mass of mossy grown. These galls are just beginning to become conspicuous on rose bushes around here and by late September they’ll reach their full size. As winter progresses all that spectacular mossy red growth withers but the larvae inside continue to feed through the early part of the winter, pupate and hatch in May as adults that lay eggs in unopened leaf buds. A wide range of other organisms take up residence in the gall, alongside the gall causing organism. Some are inquilines – opportunist squatters that take up residence in the gall tissue - while others are parasites that lay their eggs in the Diplolepis rosae larvae. There are even parasites that attack the parasites – hyperparasites – in these complex communities. You can find more information on this gall, the insect that causes it and the ‘hangers-on’ at http://hedgerowmobile.com/Diplolepisrosa.html



4 comments:

  1. This looks like what I call Robin's Pin Cushion which is caused by a gaul wasp on wild roses. I'm off to surf your link now to see if I'm correct.

    ReplyDelete
  2. I've often seen these about, and wondered what they were. Now I know.
    They have a certain beauty; the first reminds me of flames.

    ReplyDelete
  3. Hi Emma, That's the other name that I know them by too .... I gather from Arnold darlington's book on plant galls that it's a supperstitious allusion to the woodland sprite Robin Goodfellow, and not the bird...

    ReplyDelete
  4. They are a stunning colour, aren't they Keith... some of the rose bushes around here are heavily infested.

    ReplyDelete