Tommy Root
A theme for 2016 has been furthering my surveying of more difficult to find galls. Many associate plant galls with trees but they can be found on any sized plant and as such, galls on herbaceous plants can be overlooked. There are many to be found and a lot of them are quite subtle with the smallest of differences within the plants appearance being the giveaway.
My 2016 activities have included ongoing studies of Camden nature reserves, Bookham Common, my second survey of the Natural History Museum Garden, plus new sites Tower Hamlets Cemetery, Ruslip Woods and the Welsh Harp Reservoir.
2016 was my 6th year of gall surveys within Camden reserves.
At the time of writing, Camden now has galls caused by 97 species. This increased by the addition of fungal leaf spots galls caused by Puccinia vicae on Greater Periwinkle (found at Adelaide LNR, Chalk Farm).
This was my 5th year of surveying LNHS study site Bookham Common, only two surveys of Bookham for this year.
I made a concerted effort to target under surveyed host plants. New species for the study included two mite induced galls on alder and a small dipteral gall on bracken.
The bracken gall (caused by Chirosa grossicaud) consist of a small leaf roll. The tip of the pinnule is rolled downward - one white maggot ‘mines’ along the main leaf vein.
Whilst being a common species, C. grossicaud is probably atypical of most people’s perception of a plant gall.
For future Bookham surveys, I particularly want to target the lakes/ponds. I have generally under surveyed Common reed Phragmites australis – a small number of stem boring dipteral galls can be found on this species.
The Natural History Museum garden is always a pleasure to survey. The species count for the garden is now 31 species.
A new addition to the list was the semi-parasitic plant Mistletoe, Viscum album (found on Malus).
Mistletoe causes swellings within the various host plants, for which it gains nutrition – thus it is counted as a gall. The only other UK plants to do this are the dodder species.
I tried introducing mistletoe into Camden nature reserves in 2011, without (so it seems) any luck.
I particularly welcome records of mistletoe and dodder from within the LNHS study area – I personally have yet to see dodder anywhere in London.
A survey of Tower Hamlets Cemetery was undertaken in September.
The survey was the second in an annual series of surveys within the ‘magnificent 7’ – a British Plant Gall Society study of older established cemeteries in London.
The survey proved very interesting with 40 galls recorded.
As seems the case with isolated areas, certain common galls particularly those induced by mites, are not always present, that was the case with Tower Hamlets Cemetery.
However, 16 dipteral galls were found. Some of the dipteral galls (all rather small and discreet) included: small round swelling on birds foot trefoil, hollowed florets on common ragwort + burdock and a leaf roll on hogweed.
Two new site surveyed in 2016, Ruislip Woods and the Welsh Harp, are both large sites and only fraction of these areas was surveyed. However, I found 24 galls for Ruislip and 28 for the Welsh Harp – I look forward to visiting these two great sites again.
Unusually, 2016 was a poor year for the common spangle gall Neuroterus quercusbaccarum.
For those unfamiliar, these are small, round fairly flat wasp induced galls that occur on the underside of native oak leaves. Usually a very common species, this was the first year I can remember having to make an effort to find them.
In previous years, the infection rate has been fairly high with very little room on the underside of some individual leaves for anything else – but not in 2016.
I draw no conclusions, but just make the observation – it will be interesting to see how this species fares in 2017.
