Hi guys,

I've just begun my love affair with bonsai, and am building up (i think) a
good collection. I've had most of my plants for a few months now, and am
starting to experience a few problems. The one that concerns me tht most is
one of my Japanese Maples, which seems to have a pretty bad case of powdery
mildew (fine white powder on the underside of the leaves). I don't really
know what has caused it - I have 2 maples and the other is fine (it is a bit
more developed, perhaps more disease resistant). Anyway, I'm after
suggestions on what may have caused it and the best way to treat it. I've
just begun praying with a fungicide (copper oxychloride), but I'm unsure
whether this is ok or will work (the guy at the nursery said it would, but I
don't really trust him). I'm particularly concerned by the amount of blue
powdery residue the spray is leaving on the leaves. The tree is a sapling
about 9 inches high, still very slender in the trunk. I don't think it's the
location, they get good part sun and virtually no wind, so it must be
something else. I was misting them regularly, and as it is now coming on
autumn here (I live in Newcastle, Australia) perhaps I've been keeping it
too moist? Thanks in advance, any suggestions will be gratefully received.

one of my Japanese Maples, which seems to have a pretty bad case of powdery
mildew (fine white powder on the underside of the leaves). I don't really know
what has caused it - I have 2 maples and the other is fine (it is a bit more
developed, perhaps more disease resistant).
they get good part sun and virtually no wind,

There's your answer. To prevent powdery mildew, you need a little more sun, and
more air movement.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)