The best advice and the one that worked is to buy two or more
> insecticides and alternate the treatments. If you think only certain plants
> are affected still inspect the others, aphids are travelers.
> Aphids are complicated creatures bearing live young, requiring no male for
> births, and among their many other attributes they become immune to whatever
> poison you select. A few can always survive. So: if you clean off the
> infected plants keep and eye on them for several months to come.
> Claire Peplowski
> East Nassau, NY
> zone 4 - Berkshire area
Thought I'd throw in my two cents. I use Schultz insect spray for
Houseplants and Gardens. This is made with bontanical pyrethrins from
Chrysanthemum flowers and is extremely effective on aphids. I've seen
this sold almost everywhere they sell pest control products.
Superstition Iris Gardens