David in Normandy wrote:

Yesterday for the first time I tried spraying a big lupin with warm
water and washing up liquid. The plant was absolutely heaving with
thousands of aphids and starting to look quite poorly and wilting.
Today 99% of the aphids are black, shrivelled and dead. I'm really
impressed how quick and effective it has been.

I sprayed the plant in the full heat and blaze of yesterday afternoons
sun which probably helped kill off the little buggers. I'll spray again
this afternoon which also looks like being a scorcher to see if it will
kill off the remainder. I used about twice the amount of washing up
liquid as I'd use in a washing up bowl for washing dishes but this
amount was only in one of those little plant sprayers. The concentration
seems to have been good.

I'm very impressed with this "non-toxic" approach. :-)

The only question really is the "non-toxicity" of this non-toxic approach.
I've heard that the soapy water treatment will kill any predators of the
aphids as well as the aphids. Might be worth checking to make sure there's
no ladybird or their larvae, or lacewing larvae around before spraying.

Duncan