On my walk today, I noticed that the leaves and smaller branches of many of the trees around have little nodules all over them, about a quarter inch wide. They’re randomly scattered and don’t look like a natural feature of the tree. I’m guessing that it’s either caused by a virus or some kind of parasitic insect larva, although since this is New Jersey I can’t rule out tree-cancer from all the pollution.
Anyone know what these might be?
They’re insect eggs.
The lumps themselves aren’t insect eggs, as they’re woody material grown out of the tree, unless you mean that an insect embeds an egg in the tree and the tree grows a lump around it in response. That would make sense. Anyone know what kind of insects around here are responsible?
Probably gall wasps of some kind.
What kind of trees are they on?
Actually Mangetout, I remebr doing a biology project at school about this and IIRC (it was few years ago) the gall wasps are parasites of the actual eggs in the leaves.
Hmmm, are you sure that is generally the case? - I know many wasps are parasitic of (other)insect larvae/eggs (particularly some Chalcid wasps, IIRC), but many species parasitise plants directly, I believe…
From here
Not sure. Possibly some kind of small maple, I’ll take a closer look tomorrow.
Yes, you’re right then Mangetut, I was thinking of different sort of wasp and a different sort of tree parasite.