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.
Over the back of my garden in Southampton are 2 huge Oak trees and the acorns that are dropping off are shrivelled up! Sick of the squirrels too and am preparing for an influx of the pests in the coming weeks!
I agree wholeheartedly with Doug and Compass - squirrels have devastated my graden, ate all my tulips and fruit, raided several blackbirds nests and stolen food from the squirrel protected( ha ha) bird feeders and my chiicken house. Can't leave any food for blackbirds as its gone in a minute. Also got into our roof and chewed through many wires. They should be culled!
Rutland is inundated with Knopper Galls on Sessile and English Oaks. So much so it is difficult to find acorns unaffected.
Yep. Got the deformed acorns here in High Wycombe. I also noticed premature oak leaf drop from the same tree earlier this year (June/July) which worried me about the state of health of the tree. The leaves were dead, dried out and shrivelled. Could this have been caused by the same parasite?
Thank you Compass. I'm all for the active anti-squirrel (or anti-Canadian-tree-rats) action, but with the neighbouring forest bursting with the blighters, it would take an army of volunteers supported by the Forestry Commision to make much difference. Alternatively, a tree-rat starvation strategy, headed up by the biological tactics of these wasps might prove more effective? Will they turn to some other food source and be the cause of yet more damage? What feeds on the wasps and their lavae? Will we see a population boost for their predators?