Pelargonium problem

little Poll

I have repotted my pelargoniums and cut them back, to over winter in a cold greenhouse. However, on checking them today I have noticed the leaves have a large number of very, very small black things on the leaves. I think these might be some sort of black fly, although they are not moving or flying. Can anyone help please?

Pete.8

Could it just be bits of compost that have stuck to the leaves when you were re-potting them?
If it is blackfly, there's no need to do anything as the weather will soon kill them off in a cold greenhouse