Orange tree ( blight fly )

I would just wash it off with clean water and a little washing up liquid before resorting to any chemical sprays.Make sure at this time of the year that the water is just tepid.

I agree with Wyeboy - the first line of defence is as he advises. If, though, this doesn't do the trick, try Provado Bug Killer. I think it might be advisable to spray your plant thoroughly out-of-doors. to avoid breathing the spray in! Hope the washingup liquid works, though. Good luck. Tell us what happens, won't you.