mystery_gardener

Diplolepis rosae gall wasp

Mystery_Gardener
August 3, 2005

Several of these formations are growing on a wild rose bush in my sister's yard.

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Diplolepis rosae gall wasp formation

*Classification

Gall wasps are in the family Cynipidae, order Hymenoptera, class Insecta, phylum Arthropoda.

Gall wasps are small (only a few millimetres long), dark-coloured insect with a compressed abdomen. Most gall wasps form galls, though a few live within the galls formed by other species; these are called inquilines. Others feed on gall-formers and inquilines.

The exact reactions which lead to gall formation in the host plant are little understood. Basically it is a reaction of the cells of the plant to the presence of the larva.

Rose galls are produced by Diplolepis rosae. These gall wasps usually reproduce asexually; the females are about 4 mm/0.2 in long; parts of their abdomens and legs are yellow-red, while the rest of the body is black. Males of this species have been observed only rarely. The galls are a mass of reddish filaments within which are found a number of sealed chambers enclosing larvae. The larvae feed on the gall tissue.

*(this info credited to © Research Machines plc 2005)

They look like some kind of bizarre flower and are about the size of a golf ball.

Cheers,

MG

Comments (7)

  • cailinriley

    The photo is strangely attractive! And the information is extremely interesting; I've never come across one of these galls. Does the wasp do any permanent harm to the host plant? Since it's a wasp, am I right to assume that the adults are good-guys (or gals, in this case) in the garden??

    It's always fun to learn something new. Thanks for the education, MG.

  • mora

    Wow MG , that's so unexpected, would one find them on the east coast? Echoing cailinriley,s questions M

  • Mystery_Gardener

    Hi:

    The damage done to the plant is usually mostly cosmetic, but some gall-makers on cultivated plants can cause reduced vigor, and may encourage secondary invaders or infections. We think they are pretty interesting and my sister is leaving hers on the roses.

    There must be some in your area. *Of the several hundred species in the N. America, most produce galls on oaks. Galls can be found on any part of the tree (including roots), but most occur on the stems or leaves. Most of the remaining genera are on Rosaceae. The shape, size, color, ornamentation, internal structure, and arrangement of oak wasp galls is wondrously variable between species but remarkably consistent within each one.
    (*synopsis of info from the Plant Disease and Insect Clinic North Carolina State University)

    I hope to find more of these to photograph in the future. I will be sharing those photos if I am lucky enough to get some good shots.

    Cheers,
    MG

  • cailinriley

    Oaks are quite rare in my area...only Burr Oaks are reliably hardy, and they're not widely used. I have several plants in the rose family in my yard; I hope I would have noticed such a distinctive growth on one of them if it had occurred. No one on our local horticultural society chat line has ever asked about these galls, as far as I know. I wonder if -30C in winter is just too cold for the critters? Or maybe we're too dry, here. We seem (knock on wood) to get fewer pests and diseases than milder parts of the country. One of the (few) perks of gardening here. ;-)

    Thanks, again, MG. Do, please, keep your eyes and camera lens open to other interesting photos and information. One can never learn too much!

    Good gardening!

  • GRNcalgary_z3

    I live in S.W. Calgary and have galls that look very much like this picture on my red leaf rose for the second year in a row. Strangly enough, the wild rose that is trying to take over my raspberry patch has yet to have any galls and I understand that wild roses are open season for gall wasps. I will keep watching them as the season goes on.

  • Mystery_Gardener

    I have not seen any more of these galls since I took those photos three years ago. We have a couple dozen roses in our garden, none of them has ever had this anomaly. Too bad, I have a new macro lens for my camera and would love to take some closeups.

    Cheers,
    MG

    Here is a link that might be useful: Our website

  • lacertaviridis

    attn.grncalgary z3
    In Calgary NE I can confirm galls on redleaf rose but none on wild rose right next to it. I found a paper which claims
    Diplolepis rosae uses for host "woody plants of subclass Rosidae".(www.mapress.com/zootaxa/2008/f/z01796p073f.pdf) I guess Rosa acicularis is not woody but herbaceous and the wasps don't like it. This question had been bothering me for years.

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