British Plant Gall Society

Verification of Gall Records
By Margaret Redfern, 2 Victoria Road, Sheffield S10 2DL

Many members of the BPGS, armed with a copy of British Plant Galls (Redfern, Shirley & Bloxham, 2002), will find that they can confidently identify most of the common galls they encounter, at least after they have had some experience. Novice cecidologists should attend as many field meetings as they can (these are advertised in the BPGS Calendar each year), where they will find more experienced people always willing to give newcomers a helping hand. But however experienced we become, we regularly come across galls that are difficult to identify or that require determination of the causer, or for which we’d like a second opinion. The purpose of this paper is to outline the procedure of verification for those galls that create problems.

One of the aims of the BPGS is to build up knowledge of the distribution of galls in Britain with the eventual aim of producing distribution maps for every species, and in this endeavour we need large numbers of records of galls from all parts of the British Isles. So, we’d like to encourage as many of you as possible to record the galls that you find and to send your records to The Data Records Manager (her address is on the back cover of Cecidology). You will soon find that you are able contribute to this project. Most people will be able to identify most of the galls they encounter, but there will often be some uncertainties, galls that do not quite fit the key, and some that you have not come across before. The points that follow indicate the procedure that should be taken to identify and verify these problematic galls.

1. Identify the host plant as accurately as possible; ask a botanist friend to check it if you are unsure. (The advantage of doing fieldwork with a group of naturalists is that there is likely to be someone present who is able to check your identification.)
    
2. Identify the gall using British Plant Galls; if there is a problem, consult other identification guides that you have access to, and note the references you have consulted.
    
3. If possible, ask the opinion of a more experienced cecidologist, perhaps the Recorder for your area. You can find the Recorders’ addresses inside the back cover of Cecidology.
    
4. If there is still a problem, especially if you suspect that the gall is uncommon or rare, send it to one of the experts listed below (all are members of the BPGS). These people will do their best to identify your gall and will consult taxonomic experts specialising in the particular group if they have problems.
   
   It is important to include as much information as possible with the gall that you send (and keep a copy of this information). You should send:
   
   
   • The unknown gall and the part of the plant it is on (leaf, twig, flower, fruit, etc.), plus an equivalent but ungalled piece of the plant (a sketch of the gall on its plant part would be useful too).
   • The name of the host plant, identified to species.
   • The date and name of the site where collected, with its county and grid reference.
   • A summary of the attempts you have made to identify the gall.
   • Your name, address, telephone number and any email address.
   
    
5. Pack the gall and plant carefully:
   
   
   • Wrap the specimen in several thicknesses of kitchen roll/toilet paper and if the gall causer needs to be reared, put the specimen into a polybag – but do not put fungal galls in polybags. Fungal galls should be carefully dried to discourage mould from developing and then sent in paper bags or envelopes.
   • Small and/or delicate galls, and those containing live larvae or nymphs, should be put into a small rigid container (e.g. film canister, specimen tube, small plastic or tin box).
   • Ensure the specimen will be protected in the post – use bubble-wrap in a padded envelope or pack it into a box – and post it first class to the appropriate BPGS expert. Include an s.a.e. for a reply (or your email address, if available) and, if you want the specimen to be returned, include enough postage to cover this.

The BPGS experts willing to verify identification of galls and their causers in the following groups (their addresses are given at the end):

• Gall midges, Cecidomyiidae: Keith Harris
• Gall wasps, Cynipidae: the galls: Peter Shirley
• Oak and rose galls, causers and their inquilines and parasitoids: Robin Williams
• Gall aphids, Aphididae (including pemphigids): John Robbins
• Gall mites, Eriophyoidea and others: Brian Gale
• Galling fungi: Tom Preece, Brian Spooner
• Galling bacteria, phytoplasmas and viruses: Tom Preece
• Other groups, or if you have no idea to which group the galler belongs: Margaret Redfern

If you suspect that your gall is new to Britain or is a new county record, the causer must be identified and verified by a taxonomist expert in the group. If an insect, it may need to be reared to the adult stage. The BPGS expert to whom you send your gall will attempt to rear and identify it, or will send it to the appropriate taxonomist.

The experts listed are all busy people and will not welcome galls from people who have not attempted to identify them themselves. On the other hand, they will welcome problems – galls that turn out to be rare or unusual or to be new records.

The keys in British Plant Galls are designed for typical galls that are mature and healthy. Even familiar ones may cause problems if they are young or if the gall causer has been parasitised, or if the gall contains inquilines; then they may be smaller than usual or enlarged and with a distorted shape. So, be aware of this and, if possible, check several individuals to find a typical gall. Most galls in the following groups should be straightforward to identify, and should not need verification:

• Common galls that run down easily in the keys.
• Galls on oaks and roses (except for the Diplolepis galls and the small galls on oak buds and catkins).
• Most gall wasp galls on other host plants.

The main problem groups, which should be verified and their causers determined, are:

• Galls identified tentatively in the keys or where a problem is noted.
• Rare galls and those you suspect are new to Britain or are new county records.
• Galls on host species not listed in the keys.
• Most gall midge galls in swollen or closed flowers and flower buds.
• Gall midges that cause leaves to cluster together at shoot tips in herbaceous host plants and in woody shrubs; although rosettes and artichokes on trees are better known, those on Salix caused by species of Rabdophaga often also cause problems.
• Rabdophaga galls in stems and twigs of Salix (apart from R. salicis which is well known).
• Galls on Carex and on grasses (apart from Phragmites).
• Most beetle galls.
• Many aphid galls (apart from most galls caused by Adelgidae, Pemphigus, Eriosoma and Tetraneura).

Eriophyid mite gall taxonomy is confused on many host plants (e.g. Acer, Betula, Sorbus, Tilia, Ulmus) mainly because identification has relied on the gall with no reference to the mite. Work is in progress on mite determination but will proceed slowly because there are so few expert eriophyid taxonomists in Britain or elsewhere. For the time being, determine mite galls as accurately as possible and take part in the mite identification project described in Cecidology (2004, vol. 19 (1), pp. 22-24).

The publication of British Plant Galls in 2002 has stimulated searches for galls and their identification, and the last few years have seen many advances in the study of galls. Since publication, the names of some gall causers have changed and there are other improvements that will be made to the keys – a full revision is planned for 2007. In the meantime, because the stock of keys is low, the 2002 edition is being reprinted. We are taking the opportunity to update the names and to note some important amendments in a leaflet that will be inserted into each copy of the reprint. A copy of this leaflet is distributed with this copy of Cecidology so that members already owning British Plant Galls will receive a copy of this leaflet in the next number of Cecidology can use it to update the keys. We will put the amendments on to the website, too. Other papers that have appeared in Cecidology in recent years provide information to update the keys, and I recommend that you annotate your copies with this information.

Names and addresses of experts listed above:

Brian Gale, 6 Roker Way, Fair Oak, Eastleigh, Hampshire SO50 7LD.
Dr Keith Harris, 81 Linden Way, Ripley, Woking, Surrey GU23 6LP.
Dr Tom Preece, Kinton, Turner’s Lane, Llynclys Hill, Oswestry, Shropshire SY10 8LL.
Dr Margaret Redfern, 2 Victoria Road, Sheffield S10 2DL.
John Robbins, 123b Parkgate Road, Coventry CV6 4GF.
Peter Shirley, 72 Dagger Lane, West Bromwich, West Midlands B71 4BS.
Dr Brian Spooner, 31 Balmoral Crescent, West Molsey, Surrey KT8 1QA.
Robin Williams, Kynton’s Mead, Heath House, Wedmore, Somerset BS28 4UQ.

Reference

Redfern, M., Shirley, P.R. & Bloxham, M. (2002) British Plant Galls. Identification of galls on plants and fungi. Field Studies 10: 207-531.

(This article, revised slightly, appeared in Cecidology, 20 (1): 6-9, in 2005.)