Bob Hobden wrote:
Scale insects and wooly aphids won't even notice water spray unless you use
a destructive pressure that strips bark and removes all the leaves.
Actually I use water with a bit of washing up liquid to clean my Citrus
trees of scale, something they seem very prone to. I use a sprayer pumped up
as hard as possible and starting at the top go over every branch and leaf
blasting them off. It works well but you also get soaked.

reminds me, the citruses need cleaning off before the winter. They've
had a lot of sooty mildew this summer in the greenhouse.
I've not found anything other than a wet cloth and elbow grease to remove
scalybugs. :-(