You are here: www.nhm.ac.uk > Nature online > British natural history > OPAL home
Cushion Xanthoria

You are here: Home » OPAL Blogs » Sarah West's blog

 

Sarah West

Update on the enormous gall

22 February 2010
After I wrote the last blog entry, I emailed the gall expert who had been on the course, and he had this to say about our photo....
"Galls are fascinating and intriguing structures. They are parasites on plants. Each gall is an abnormal growth produced by a plant host under the influence of a gall causer. The structure produced by the host isolates the gall causer but the causer is still able to draw nutrients from the plant as its food source. Several organisms cause galls including gall wasps, gall midges, gall mites, and a few examples of aphids, moths, beetles, micro fungi, bacteria and nematodes. The causer lives within the gall for at least part of its life cycle. The study of plant galls is called Cecidology.
I think the strange structure you discovered with your team on Sunday morning is probably an example of a gall caused by the bacteria Agrobacterium tumefaciens.  Initially, from Adrian’s description I thought it may be a fungal gall, Taphrina betulina which is common on birch and known as the ‘witches’ broom’. I wonder if you might have seen this somewhere, it can be quite common. Adrian assured me the tree was not birch"
So, looks like it was probably caused by a bacteria, thanks Tom!

The biggest gall ever?

15 February 2010

Yesterday I spent the whole day in Harrogate helping run an OPAL / Yorkshire Naturalists Union course about how to put biological recods into Excel. Those of us new to biological recording went outside in the sunshine to do some species recording. Despite it being cold and damp, we saw lots of wildlife - the highlights were a nuthatch and this amazing gall...

Note Adrian Norris standing underneath the tree to give you an idea of scale!! The other interesting thing about this gall was that grey squirrels are now using it as a drey, we saw one poke it's head out of the top!

The British Plant Gall Society website says that galls are abnormal growths produced "under the influence of another organism". Organisms that can cause galls to grow include certain types of fungi, aphids, mites, some species of flies, viruses and bacertia. Unfortunately we couldn't identify the tree, which is one way of trying to identify what may have caused the gall, but one of the course attendees specialises in plant galls and he suggested that this one might be caused by a bacteria.

My friend Ellie just came in and asked if the galls damage the tree, I said they probably didn't, can anyone confirm this??

OPAL Yorkshire and the Humber

I'm Sarah West, OPAL community scientist for the Yorkshire and Humber region. My blog will keep you up to date with all the fun stuff we’re doing across the region.