Could anybody identify what it is...
There wasn't as many as this just the odd few up the main trunk I squished them then hosed down the tree should have taken some pics first..
Firstly is it serious and how do I treat it?
wipe them off with cotton wool soaked in methylated or surgical spirit. they are a sort of scale insect. the white coating is waxy and repels normal sprays.
the tree looks awful at the moment the leaves are yellowing but I put that down to the ground being bone dry when we came home from holiday and next door (semi detached) have just had a new drive installed, I also put it down to builders may have upset the roots. . This is how I came to notice the little critters as I went out to prune all the bad looking leaves off and shape the tree, I keep it small like a lollipop