Posted: 18/06/2015 at 10:48
Yes, you only need a small squirt per pint of lukewarm water - I use Ecover. But I only do this as a last resort and haven't had to do it for a couple of years now, which is a good thing because soapy water still harms beneficial insects as well as the aphids.
I've encouraged beneficial insects and birds into the garden and they keep the aphids down to a minimum - when the aphids first appear earlier in the season if there are any bad infestations I brush most of them off with my fingers or use a jet of water from the hosepipe. Otherwise the ladybirds, wasps and bluetits deal with them. No problem. .