lagagnon writes
We have two varieties of inherited apple tree, varietal unknown. This
year on both a few of the upper leaves are curling up, with a white
powdery substance on the leaf. This does not look like insects, but I
have not taken a magnifying glass to them yet - to me it looks more
like a fungus. Any ideas what I am up against and what I might spray
them with?

Mildew. If it's only a few leaves, I'd just remove the affected leaves.
For prevention, make sure your trees are receiving adequate water.
--
Kay