I use washing up liquid diluted with water and spray at the first sign of an aphid. It works for me. Taking off the spent heads regularly helps as well, plus having plenty of plants around which attract predators so plenty of bug friendly plants.
Yes lupin aphids can cause big problems to the plant. Diluted washing up liquid works well at getting rid but I have to repeat the spraying a few times. I am always on the lookout for them before they do too much damage.
The threads a little old but I figured I'll give it a bump as my lupin spires are just forming and the aphids have made an appearance.
My technique has been cupping a hand underneath them and then gently running my other hand up the stalk and spire. Then once a load of the horrible little blighters fall into my cupped hand I give them a hearty round of applause. Squish
A crude method but the numbers have dropped significantly over the last 2-3 days with one thorough application per day of this treatment. Don't forget to wash your hands afterwards though!
I'm gonna get a little squirty bottle when I go the shops later to mix up a concoction or two to try out on the plants - So far I've read that diluted garlic powder, pepper or washing liquid can work. A season of experimentation awaits.
A squirt from the hose or a bottle is the easiest way Bob, or the hand method as you've discovered! No danger to any other beneficial insect too.
The best solution of all is to get birds in to eat them. Hanging small feeders near susceptible plants gets them used to particular areas. Blue tits especially will hoover them up.
I didn't know birds would have them - I'd read somewhere that they were only inroduced in the 1980's and nothing has really developed an appetite for them. I don't use any chemical sprays in the garden so I'm keen on a more organic solution to these aphids as they have ran riot a few times over the years when I've left them to the ladybirds. Unfortunately, the ladybirds seem to appear later in the season and the damage has been done.
I've a couple of spots in the same border where I can hang some small feeders so I'll add them to today's shopping list. Even if it doesn't solve the aphid problem it'll be nice to encourage a few more birds into the garden - Something nice to look at while I'm doing the dishes and they'll definitely have a peck at any slugs!