That sounds like Scale Insects - they are small sap-suckers that create a brown "scale" as a protective shield with fluffy white substance beneath and behind the scale, quite common on the trunks of Acers and other trees, particularly in Urban & suburban areas.

Once they have attached to a plant they cannot move so if you only have a small-ish number just rub them off with a soapy sponge, being careful to collect them in a pot/bowl etc - the white bits contain egg masses too, so try to get as many as you can.

They are highly resistant to most insecticides, but can be killed with fatty-acid based sprays if you have a very large infestation.

Thanks for that ,we will try soapy sponge to remove the blobs.