You may have seen an unusual but very abundant difference with many acorns currently on Oak trees this year. On the left is a phenomenon that has affected acorns all over the country in abundance through this year - more so than recent years which we can only assume is climate based. Whilst they appear to have exploded, the actual reason is quite fascinating:
These weird objects are called 'knopper galls' and are caused by a tiny wasp called Andricus quercuscalicis - this it is a parthenogenetic gall wasp which lays a single egg within a leaf bud. We have found these in abundance on the mature Oak's on at Barby Meadow Woods. The wasp lays its eggs in flower buds which, instead of developing into acorns, grow into these popcorn-like galls that provide a home for the wasp larvae and pupae through the winter.
The causative gall wasp first arrived in the UK sometime in the early 1960s, having slowly spread across Europe from Turkey, and colonised rapidly once it arrived in England, so it’s now well established throughout most of Britain and well into Scotland. The damage that it does to acorns led to widespread speculation that it would destroy the acorn crop and would be a major threat to the future of oaks in Britain, but infestation levels vary a lot from year to year and it’s unlikely that this minute wasp poses a long-term threat to our national tree.
