What's this on my acer??

Today I noticed some ''white stuff'' on the lower main stem of my Acer. At first I thought it was 'cuckoo spit', but it was sort of like cotton wool and there were some flat light brown insects in it too.:cnfs: I wiped it all off the stem.....sorry, should have taken a pic first?.....but what could it be and is it doing damage. I've had the acer about 3 years now and it's doing really good......I'd hate to lose it:(
Any advice would be gratefully appreciated.

 

Sounds like "wooly aphid" you can wash it off with soapy water or squish it with your fingers or use something like Provado Ultimate Bug Killer.

 

Thanks walnut!