Topic: Mossy Willow Catkin Gall - Causer unknown (Mossy Willow Gall)?

I'm struggling to work out how to import the Mossy Willow Catkin Gall onto our database (using UKSI).  I can't find a suitable entry so it may possibly need adding, or I may be missing something - please let me know either way!

We have a number of records for it, the background I've been given by one recorder is:

"Its listed in Redfern, M, & Shirley, P. (2011)  British Plant Galls (2nd edn). FSC
This is a standard text.   Extract from p.291: Salix: Galls on or in catkins 
‘Catkin grossly distorted forming a green witches broom or a hard woody lump [ . . ] growth sometimes appears to be attached directly to a twig or branch; on many Salix species; frequently found, particularly prominent in winter
Virus?, Phytoplasma?
A mite Stenacis triradiatus [. . ] has been found in association with this gall and was originally thought to be the causer before Westphal & Michler (1975) demonstrated the presence of virus particles in the cells. At present, the causer of this gall is uncertain; it may be caused by a phytoplasma [ . . . ]’

The full reference of the note given in the text (Westphal and Michler 1975) isn’t listed in the References section but it must be this: Westphal, E. and Michler, P. (1975) Demonstration of bacilliform particles in "Wirrzopf" type malformations appearing on certain Willows, C. R Acad Sc. Paris, 281, D, 403 - 405..  (see https://www.insecte.org/forum/viewtopic.php?t=134327)

On Bladmineerders, a Dutch website run by Willem Ellis which I use a lot, it is listed under the mite but with this text: ‘Galls like these are commonly associated in the cecidological literature with Stenacis triradiata, albeit not without some hesitation, because generally several more gall mite species co-occur in the gall. Presently one supposes that a mycoplasma, rather than eriophids, is the primary causer (Pye, 2012a) of these galls, that often are addressed with the German word “Wirrzöpfe”.’ https://bladmineerders.nl/parasites/ani … riradiata/
I notice that neither the gall nor the mite its not on the BPGS checklist, though.
An alternative might be to import it under the mite’s name, but it doesn’t feel correct to me."

Any advice appreciated,




Re: Mossy Willow Catkin Gall - Causer unknown (Mossy Willow Gall)?

Hi Kirsty

That's a really fun problem because you're spot-on in that where you have these communities but no one causer has been identified it can be tricky to work out what to do. With lichens (fungus+alga) they are listed under the fungal name but here we really don't know who is the causer and who might be just inhabiting the structures. We could do this a number of ways:

* It's physically possible for us to list a vernacular taxon so we could have "Mossy Willow Catkin Gall" which you could record against but then which kingdom would we put it in? It's not one thing or another so it might have to (heaven forbid!) sit with a parent of just Biota 

* We could list it under the mite Stenacis triradiatus and then it would at least sit in a taxonomic structure - do we know if other mites in this genus are gall causers?

With galls I would be asking myself which of the inhabitants has ONLY been found in this gall, and which have been found in other situations, but I suppose (again) not enough is known about any of them to be sure. Perhaps we could look at what is known about the relatives of these organisms too?

Happy to go with whatever you suggest :)

Chris R.

Chris Raper, Manager of the UK Species Inventory, Angela Marmont Centre for UK Biodiversity,
Natural History Museum, Cromwell Road, London, SW7 5BD.  (tel: 020 7942 5894)
also Tachinid Recording Scheme (http://tachinidae.org.uk/)