In article , jay
writes
Hello There,

I wonder if anyone can tell me please, what the powdery black substance is
that is covering my leaves on my Citrus Tree, Bay Tree and my Nectarine
plant is? It also looks like it may be spreading to my Grape Vine. All these
plants live in my green house in the North West of England. Ive looked for
answers through the web, but im not 100% sure.

On the bay tree and citrus, it is almost certainly black mould growing
on the sticky exudate from scale insects. Look under the leaves above
the black are, and you will see oval brown scales. If you get rid of the
scale insect, you will be able to wash off the mould, and it will not
recur.

If you have an established colony of scale insect, then it will quite
happily spread to nectarine and any other adjacent plants.

I take them off manually (scraping with finger nail), and cut off really
badly affected roots to reduce the chore a bit.

Once you think you've got rid of them all, keep checking every month or
so for ones you missed.


--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/edward/index.htm