I usually just squish aphids with my fingers. I found it takes a lot of water pressure to knock those things off stems. If you'd rather not do any squishing
, the Safer soap solution is nonpoisonous so I'd try that instead of anything stronger. I think the label says to wash off after 30 minutes so leaves aren't burned by the spray. Probably it's not good to use in bright sunshine, either.
Marcia