Walking through the pretty woodland nature reserve of Fron Wyllt, I looked at the leaves of some Alders by a small bridge over the rapidly flowing stream.
On the first day I noticed that they had been a bit frazzled.
On the second day I actually thought about it, and wondered whether they were sawfly/slugworm larvae that might be responsible. It sort of occurred to me (very slowly) that I might not have seen this damage on Alder before. It looked a little like the shredding or skeletonisation of beetle larvae damage (as I have seen regularly on Viburmum in recent years) or slugworm damage (as I have seen in the past on Birch). Eventually I found a larva which I thought I recognised as a slugworm style of sawfly larvae. A nasty-looking glossy black caterpillar.
When I got home I saw references to Alder Sawfly, but that is white and spiky, so it was not that. By chance I came across many US references to an Alder Flea Beetle with very similar larvae and blue adults. But this apparently doesn't occur in Europe. I was now intrigued and I finally came across references and photos relating to Agelastica alni, a beetle thought to be possibly extinct, but rediscovered and apparently spreading across several parts of the UK. Oddly enough, it looks very similar to the Flea Beetle from the US.
Here is a photo of a larva on apparently fresh damage, near the base of the leaf.
And another, with slightly older damage,
Here is a photo of older damage, no larva seen.
And a photo of skeletonised leaves against the sky, indicating what potential damage could be done to the Alders along our streams and rivers.
This is the site where the worst damage was seen,
No comments:
Post a Comment