problems with Olive tree

[laptatony]

One of our Olive trees, the leaves are turning black, seems a lot of midges and hornets around it, suggestions what to do?

[Medjoul1]

Hi laptatony, do they look anything like these? I have this to varying degrees on all my trees and its caused by a small green caterpillar about one centimetre. I have sprayed for olive fly and this doesn't seem to affected the caterpillars but there is fresh growth on the trees so I'm not unduly concerned.