Grey aphid on brassicas

Hi there my normal approach would be dilute washing up liquid sprayed on them.
Recently just left them to the ladybirds ...but you need to have some of course!!
Good luck HH

Thanks I  will try the soap solution to clean of the sooty mould, does anyone know - do the plants recover after the clean up?  And thanks for the tip about the nasturtiums - do french marigolds help too?

I sprayed my brassicas with soapy water about 2 weeks ago and they are just starting to recover. They were really badly infested and lost quite a few leaves! New growth now though   

Buy a Garden Spray attachment for plastic bottles and you wont look back 

Fill an old litre bottle with water and add a teaspoon of washing up liquid. Check out that there are no ladybird larvae present. Cup affected leaves in your hand and spray directly onto aphids. It kills them immeditely on contact by stopping them breathing through their skin and it is enormously satisfying!

Thanks, will get at them tomorrow.  Now found some in the greenhouse house on my peppers so they will get some too.