Scale insect on plum tree

[miniplot]

Hi, I have a young plum tree which has just finished flowering and I have noticed scale on the young growth. Does anyone know ofa way to eradicate this without chemicals as I want to eat the fruit and not poison myself! Incidentally, I also have it on a Corylus contorta and a few other shrubs, and I've never managed to get rid of the little blighters!