By Shazziepx
Surrey,
United Kingdom 
Hello we have a potted 4ft Olive Tree, it's leaves have turned black, it looks like a coating with stick bits on. We have been told it's black sooty mould. What is wrong with it in your opinion. Our pretty little tree looks so lifeless. Would it be advisable to spray it and pull all the leaves off in order to start again and should I repot it.
Thank you for your all comments. We have since repotted and sprayed our little tree, unfortunately all the leaves have fallen off. Our fingers are crossed as there is still green in places on the bark, we will have hope. Any further comments are welcome.
Any further advice welcomed.
20 Apr, 2018
Answers
Olive trees do get scale in the UK, so have a good look as Seaburngirl says. Once you get rid of the scale infestation, the sooty mould will disappear over time, though you can attempt to gently wash it off with a very mild soap and water solution. Info below
https://www.rhs.org.uk/advice/profile?PID=138
20 Apr, 2018
Thank you for your comments. We have since repotted and sprayed our little tree, unfortunately all the leaves have fallen off. Our fingers are crossed as there is still green in places on the bark, we will have hope. Any further comments are welcome.
29 Apr, 2018
that does look like sooty mould. you need to check your plant for scale insects or aphids. they secrete a sugary waste 'honeydew' and then the sooty mould grows on it.
if you find any insects then a systemic insecticide would be my choice to deal with them. or a soap solution spray if you don't want to use insecticides.
then to improve the appearance you could gently wipe each leaf with a mild soap solution.
repot and a good feed will give it more strength to grow new shoots. I wouldn't prune it yet.
20 Apr, 2018