"John wrote in message
We have a (previously neglected) Camellia in the garden, which a
black/grey
soot-like residue on some of the leaves and a few buds. Is it likely to be
a
fungus? Treatment?

Sooty Mould growing on the secretions from sap sucking insects.
Camellias do suffer from scale insects (as do Acers) so check the leaves and
thin stems above the blackened leaves and see if that is the cause. They
look like 1cm oval brown scales which will come off if pushed.
When breeding they go woolly and can then be confused with Woolly Aphids
although you can still see the scale if you look.
If it's only a smallish plant you can use a high pressure spray of ordinary
water with a touch of detergent to dislodge them, they can't crawl back once
adult. Keep the sprayer well pumped up. You will get wet though! :-)
I do this for our Citrus which are also prone to them.
Otherwise, there are proprietary sprays available.
--
Bob

www.pooleygreengrowers.org.uk/ about an Allotment site in
Runnymede fighting for it's existence.