I notice at the coast near Vancouver in the past few weeks - an increasing silver blue-gray haze on the leaves of the native "Big Leaf Maples" (the really big native ones many of have in our gardens and pastures (or out at UBC forest for example) Acer macrophyllum - Wikipedia (Acer macrophyllum) why is that? It happens each year to some of the Acer m. trees it seems - but there has been no rain and lots of sun - so why does mildew develop (I associate mildew with moisture - it would seem i'm not correctly assuming cause-effect) is it mildew - is there a technical term? Just curious. i notice other deciduous like alders or salmon berries or even blackberries don't have mildew - so why are maples the chosen host? I don't intend to fix or remedy this - as it doesn't seem to kill the tree - just looks strange in late summer before the October rains and leaf drop. thank you!