Miniature Orange Tree

I have a miniature orange tree which is situated at the present time in our conservatory. It suffers from sticky leaves, which has now found its way to the tiled floor. How do I get rid of this sticky liquid ? I look forward to your reply.

 

Its probably down to scale insect or possibly aphids.
A spray with a good insecticide should sort it out.

Sometimes you can get sooty mould growing on the leaves, it feeds on the sticky excretion of insects.
Its a black kind of colouring that washes off.