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June 3, 2009 : Salix species and Rhabdophaga rosaria
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Plant Family / Families: Salicaceae
Scientific Name and Author: Salix sp.
Name Location: Calgary, Alberta, Canada
Today's images come to us from Suzan D. Suzan posted the photos for identification on the UBC Botanical Garden forums in 2004. She cleverly called these "woses." Original post.
Although the structure in the photo looks very much like a green rose, roses do not grow on willows. And while Suzan never found the insect, we believe this to be a gall caused by Rhabdophaga rosaria, the European rosette willow gall midge. Galls are abnormal growths found on plants that can be caused by parasites such as insects, mites, fungi or bacteria. Insects, particularly wasps and midges, are the most common cause of galls on plants. Plants form the galls in response to ovipositing or feeding by the insect, or from infection by another agent. The gall is an attempt to surround and isolate the invader. In the case of insects, the gall actually forms a protective chamber, where the larvae can develop safely away from predators.
Many types of galls exist. Many are shaped like balls or blisters. They are still unusual things to find in the garden, like this one from the UBCBG forums. In North America they are most commonly found on Fagaceae (oaks), but are also often found on Salicaceae (willows), Rosaceae (roses) and Asteraceae (asters). In general, they cause little damage to the plants and most are not considered to be significant pests.
Further reading on plant galls:
- Insect Galls, University of Florida Extension
- Gall-Making Insects - John A. Byers
- To Be Or Not To Be A Gall, Wayne's Word http://waynesword.palomar.edu/pljuly99.htm
Posted by Eric La Fountaine at June 3, 2009 3:43 PM
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Comments
Posted by: Carolina at June 3, 2009 6:07 PM
Oh wow! Would I love to see that one! I love galls. Am waiting for someone to write Galls of the Northeast. There is a book for CA. Meantime I will enjoy the links you provided. Also add poplars: we have a poplar petiole gall in NH and I've seen galls on the edges of poplar leaves elsewhere.
Posted by: Deborah Lievens at June 3, 2009 6:25 PM
Amazing to think that's a gall - it would be nice to find out exactly what insect caused it!
Posted by: Ann Rein at June 3, 2009 6:36 PM
wow! at first look it looked like a miniture cabbage, although I knew it wasn't. it does look like a rose also. how interesting. thank you for posting. I love learning every day from your site
Posted by: Lanie at June 3, 2009 6:37 PM
How interesting. I am used to galls on goldenrod. This is so enlightening.
Posted by: Meg Bernstein at June 3, 2009 6:48 PM
Absolutely stunning! I've seen a lot of galls but this takes the cake as the most incredible.
Here is a much less impressive gall growing on Baccharis pilularis:
http://www.flickr.com/photos/ericinsf/3251002262/
And the lovely larvae at the heart of the gall:
Posted by: Eric in SF at June 3, 2009 7:12 PM
I have heard that someone is studying galls in relation to cancer. Something triggers the plant cells around the egg to grow into a gall instead of a normal leaf or stem or whatever. It seems one or more genes are either supressed or activated. Or both? I would like to know more about this, if anyone can point me there...
Great pictures, I guess it's no good looking for a "willow rose" in the New World!
Posted by: Connie at June 4, 2009 5:25 AM
I have never seen a gall that looked so like a flower. Thanks for this interesting photo and discussion.
Posted by: bev at June 4, 2009 6:10 AM
I have many willows at my home in the midwest. They usually get galls on the stems resulting in abnormal growth. They certainly are not beautiful! If I had to have a willow gall, I sure wish it would be this one! I could cut and sell those to a florist! ;-)
Posted by: Adriana at June 4, 2009 6:28 AM
For those interested in identifying galls and the organisms that induce their development, there is the book Plant Galls and Gall Makers, by Ephraim Porter Felt, published in 1940 by Comstock Pub. Co. and reprinted in facsimile by Hafner Pub. Co., New York/London in 1965. The author was Director and Chief Entomologist for Bartlett Tree Research Laboratories, Stamford, CT. The scope is the U.S. After a general discussion of galls, the bulk of the book is comprised of a key to the galls and their causal organisms, organized by plant families.
Posted by: Charles Tubesing at June 4, 2009 6:45 AM
To Carolina, who had never heard of galls caused by insects: I believe that's what they are referencing, in 19th century English literature -- "oak apples."
Posted by: Deb at June 4, 2009 7:46 AM
Connie, note that the photos were taken in Calgary and if you follow the link to the original post on the forums, one of the Friends of the Garden recalls seeing them frequently in the Yukon, so you will find this in the new world. We could only find mention of the European rosette willow gall midge causing this type of formation. The insect probably was brought to N. America unintentionally, but it could be a case of convergence and the gall may have been caused by a different species.
Posted by: Eric La Fountaine at June 4, 2009 8:08 AM
Superb photo of an intriguing curiosity. As, a child in England I remember the "robin's pincushion"
on wild rose. Galls can really start the wheels turning! Thank you, Suzan.
Posted by: Tom Wheeler at June 4, 2009 8:25 AM
The morphology is so close to a 'normal' flower that one wonders if the genetics for this particular flower morphology live inside a LOT of plants and this particular gall insect took advantage of it.
Posted by: Eric in SF at June 4, 2009 10:04 AM
It's a rose! It's a cabbage! But no, not even a cabbage rose. Utterly fascinating, and quite beautiful. Great pictures.
Posted by: Annie Morgan at June 4, 2009 11:18 AM
to be or not to be a gall is a good read
the pictures are ever so good
my i surely did have the gall to say that
Posted by: elizabeth a airhart at June 4, 2009 4:02 PM
Awesome write on galls! I have wondered about their purpose. Besides being protective wouldn't the extra growth also feed the 'baby'? I do have one of the rare fungal caused galls on my Forsythia. Also, I met a guy whose uncle wanted to induce galls to his oak tree because he LIKED them!
Posted by: Dana at June 4, 2009 4:31 PM
always interesting around here
i have been outside on the grounds this hot night now that i know what i have found but
could not put a name to -thank you
this post took a lot of gall to post did it not
Posted by: elizabeth a airhart at June 4, 2009 5:45 PM
sorry about the double post
Posted by: elizabeth a airhart at June 4, 2009 5:46 PM
Galls are just fascinating! I've never seen one other than the blisters or balls on Fagaceae and Salicaceae! I've never even imagined an Aster or Rose gall...any chance of seeing one posted?
Posted by: Justin at June 5, 2009 10:33 AM
Please share your comments about the photograph(s) and accompanying write-up. Telling a story about the subject of the photograph(s) is also much appreciated! If you have a gardening question, the best place to ask is on the UBC Botanical Garden Forums. Thank you!
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Botany Photo of the Day is a project of the UBC Botanical Garden and Centre for Plant Research, located in Vancouver, British Columbia Canada. UBC BGCPR is a department of the Faculty of Land and Food Systems within The University of British Columbia.
Never heard of (insect caused) galls before, this is so interesting. How beautiful they are, until you know there is a larva (eeww!) inside!