As I've wandered the trails around The Lodge recently, I've noticed something strange. Where there should be smooth, shiny, ripening acorns dangling from the oak twigs, there are distorted, crinkly growths which - to my eyes, anyway - look a bit like Ferrero Rocher chocolates...
It turns out that this is the work of a small wasp which goes by the snappy name of Andricus quercuscalicis. The weird growths themselves are known as 'knopper galls' - the word knopper being derived from a word for a knob, stud, tassel or hat.
The 'gall' is the growing acorn's response to the wasp grubs developing inside after eggs were laid there earlier in the year. In a similar way, you might have seen the robin's pincushion gall before - it's a common sight on wild rose bushes, with a tangled mass growing from the stem eventually turning red.
At The Lodge, at least, there are not many acorns to be found this autumn. The galls are turning brown and falling off the trees, and the newly-hatched wasps making their escape.
Jays are famous for their love of acorns, able to store away as many as 5,000 for a rainy (or cold) day. What will they do here this year?
As members of the crow family - clever, bold, adaptable and omnivorous - I doubt jays will go hungry. They just might need to look for some different foods in different places, so I wonder if that could mean an influx of jays to garden bird tables? In the same way, might we see squirrels launching a hunger-fuelled assault on our feeders?
Let us know what you see!
Have you spotted knopper galls on your local oak trees? Leave a comment and let me know.
Squirrels get a ridiculously bad reputation, most of it undeserved. Some people seem to blame them for the fall of The British Empire. They've been here at least 40 generations now in areas, pushing the term invasive species. Red squirrels are though to have been introduced from Europe just a few hundred years ago. Reds verses Greys was evolution in action and entirely human's fault. And yet some people still want to go out and kill them as if they burglars. They are not burgling your home they just want some of those juicy nuts and other food you temptingly put out on your feeders every day. Give them a break, and a separate feeder with shelled peanuts, while there are shelled peanuts in their feeder, they'll ignore everything there is.
After reading all of this I think I must have the most well behaved Squirrel visitor in the whole of the south of England. He is old now but I collect acorns for him and he is quite content taking them and leaving everything else for the birds. He does make quite a few holes in my front lawn when he hides the acorns but I am not bothered about that as my garden is more about wildlife survival than pretty, pretty for me., and it is more moss than grass so his digging actually benefits the lawn as long as I remember to remove the little oak seedlings the next season. I do not agree with a mass eradication as nature has shown in the past how eradicating one species or at least taking it to near extinction can cause a major imbalance within other species both Flora and Fauna. As much as you don't like them or view them as a pest they in their own way are part of the natural balance. We have Bees struggling to survive, an overload of magpies because their natural predator has been hunted to near extinction in some areas, they in turn kill baby pigeons, and take the young from other nests including house and tree sparrows that are also struggling to survive. The best way is to allow nature to address the balance.
I should have read Katie's note and the Wiki article. Turkey oak seems to be a double edged sword. Is it's support of the wasp's reproduction in spring more damaging than the benefit of acorns in the autumn?
At Wimpole Hall, Cambs., all acorns on English Oak seem to be affected by the gall wasp, but one large specimen of Turkey Oak, standing between 3 affected Engish oaks, was completely clear of galls and had a good crop of normal acorns. I do not know if this species is equally attractive to Jays but there were quite a few of them around. I know that some oak-feeding Lepidoptera find the leaves of turkey oak either too tough or distasteful, so perhaps the wasp is also repelled. The big question is therefore,"are the acorns palatable?"
Hi Katie re my first post yep i've just this minute had my first Jay in the garden.
Wow, that's a lot of comments!
The wasps which cause the acorn galls need the presence of a Turkey oak nearby to complete their life cycle, so presumably this problem will only be seen where those non-native trees are present. See: en.wikipedia.org/.../Andricus_quercuscalicis
I don't think there's anything which can be done to the affected trees, and perhaps the wasps have had a particularly successful year. Next year might be different!
As usual, grey squirrels have polarised opinion. If you want to discourage them from your garden, we've got plenty of suggestions: www.rspb.org.uk/.../greysquirrels.aspx or you could try asking for tips on the Community: www.rspb.org.uk/.../14005.aspx
Regarding squirrels' impact on bird populations, there's been quite a bit of research done, which you can read about here: www.rspb.org.uk/.../Predator%20Report_tcm9-177905.pdf
I've seen some oak trees chronically and extensively infected with this problem. However jays seem to be increasing both in numbers and boldness. One reason may be their adaptability re. food sources. They take very many fir cones in my local cemetery.
As for grey squirrels - persistent little beggars - I saw a cat kill one in the street near me.
The balance of nature is complex and ever evolving.
We live in a suburb of Birmingham with lots of mature oak trees, which we pass on our way to my daughters' school. Acorn numbers vary from year to year, but this year for the first time my 9-year old picked up something that she described as a 'disabled acorn', which I think might be one of your galls. They are small and brown, and we have found them scattered on the ground. There have been some acorns too, however not all that many as yet. Will try and collect some galls to photograph once it stops raining...
more for John Cooper re the Robin's pincushion gall - have a look at this: www.bugsandweeds.co.uk/galls%20p1.html
John - that's a Robin's pincushion gall
Just a thought on the Gall/Knopper Gall/Wasp thingy, for the first time ever I saw a couple of wild roses today that 'may' have been affected too, can anyone confirm or is this something different
It is not an "anti-squirrel rant", more a recognition that grey squirrels are an alien species in the uk which do what alien species do anywhere, such as rabbits in Australia or foreign bees in South America - increase exponentially and cause havoc among other species, and sometimes with people (see bees). As far as I know the only legal ways to deal with squirrels are to trap them in squirrel cages and take them to a vet to be humanely destroyed, or to shoot them. I understand that it is not legal to drown them, or to release them into the wild once caught.
On a sunnier note, squirrel-wise, I recently visited Brownsea Island (in Poole Harbour) - one of the last remaining refuges for red squirrels in southern Britain - and was delighted to spot LOTS of reds! They're doing really well there. Didn't think to look at acorns, so I don't know if the wasp problem has reached there, but the squirrels certainly seemed to be finding enough to eat.
Have there been any reasonable proposals - preferably humane! - to reduce or control the numbers of grey squirrels in Britain? I'm new to the UK and have been saddened to see how the transatlantic tree rats have taken over and almost eradicated the native squirrels. I know it's not the greys' fault personally, so to speak, but especially as I come from Australia - where introduced species (mainly from Britain!!) are a HUGE and devastating environmental problem - I just wish something could be done about this.
I had a quick look at several oaks along lanes in SW Norfolk yesterday. Some trees seem unaffected, but about half had strange shaped acorns - but also healthy acorns on the same tree. This seems to be turning into an anti-grey squirrel rant - I don't have much of a problem with them - but they are certainly increasing in number. OK they raid the bird feeders, but the real demons at garden-wrecking are slugs - but I can't kill them as the hedgehogs will go hungry! However to return to the acorn problem, there are fewer acorns than usual on all the oaks I saw yesterday - and fewer conkers on the horse chestnuts. I guess this is the result of the weird weather this year which has affected apple and pear crops locally. Oh and the jays are also on the increase round here!