Welcome to GOY Mrpotatoehead,I wait in anticapation for the answer to that one my lovely purple hellibore is covered!

If you,re not averse to using chemicals, then you can use sprayday greenfly killer made by bayer garden, kills greenfly blackfly whitefly caterpillars, and a host of other nasties, use it in a sprayer, available from any gc or good hardware shops.

You could try looking up Garlic in the alphabet at the bottom of the page. Bamboo has some advice about using it as an insecticide.