potted weeping fig with sticky leaves.its about 15ft.

They tend to do this, i think it may be an insect sucking sap and then they leave a sticky residue on the leaves. The sticky ness may go black as moulds move in on the stick. Can be washed off with a very mild soapy solution and looks worse that it is. A fig in a garden where i work has it every year with no detremental effect, Just clear leaves up at end of season and bin or burn just to lessen the likely hood of it spreading!