The Beech Leaf-Mining Weevil Orchestes fagi is easily recognised by the combination of a very thin mine from the midrib of a Beech Fagus sylvatica leaf to an expanded brown blotch on the leaf margin near the tip (left).  Below, you can see the oviposition (egg-laying) scar on the midrib (middle), and holding the blotch to the light should reveal the larva inside.  Affected trees are easy to spot as the brown leaf tips stand out (right).  Before reporting them, ensure that the browning is actually due to the beetle mine, and not to some other cause.