Friend or foe?

If they are the squishy type of scale, I don't think you even need to use anything more potent than water as you can manually mush them with a soft brush.

 

Thank you @Thevictorian, that's my plan for this afternoon!

 

I probably spent too many years breathing evo-stick fumes, I often went home from work on a high in the 70s and 80s.

 

All done! I spent about an hour this afternoon using first a dry washing up brush (garden designated one!), a soft wire brush and some water for the stubborn areas and an old toothbrush for hard to reach places. They came off quite easily, but I wouldn't recommend wearing a white shirt when doing this ! I then gave all the branches a hose down. It looks a lot better now .

 

The simplest way to source such a product is a quality screenwash containing isopropynol, often available as a RTU handspray (squeezybottle trigger). This works on all insects but will cause them to literally disintegrate, hardly kind, but is effective, especially on wasps ! Do not use in an enclosed space or with naked lights.