I recently planted a bunch of saplings in my yard and two of them, a plum tree and a beech tree, haven't budded yet. I worry they might be dead. Both the beech and the plum are covered in small flies that I've never seen before. I'd like to understand more about these flies so that I can either save these two trees or prevent their future replacements from meeting the same fate.
Some images of the flies:
[url=https://img3.freeimagehosting.net/image.php?2d01487786.jpg][img]https://img3.freeimagehosting.net/uploads/th.2d01487786.jpg[/img][/url][url=https://img3.freeimagehosting.net/image.php?ae8fdd5ffa.jpg][img]https://img3.freeimagehosting.net/uploads/th.ae8fdd5ffa.jpg[/img][/url][url=https://img3.freeimagehosting.net/image.php?32612c2a5d.jpg][img]https://img3.freeimagehosting.net/uploads/th.32612c2a5d.jpg[/img][/url]
What are these flies? Why are they on my trees? Are they damaging the trees? If so, how do I get rid of them?