They infested my tomatoes horribly a couple of years ago. Some insecticidal soap and picking them off by hand did the trick.

I was going to mention the same thing as jrossi: insecticidal soap. You're also supposed to blast them off with a water wand. Not the jet powered setting, but something like this.

Wait, I may be thinking of mites. You can rinse mites, I'm not sure about aphids.

Aw, I had a hibiscus with an aphid infestation and the only way I could get rid of it was to get rid of the plant. I'm still sad about that one. I hope you have better luck than I did Taz!

Come to think of it, the same thing happened to a pink hibiscus I had in the front porch area. The little bugs get into the flower and kill. From what I remember the flowers wouldn't open and they were dropping. I scoffed that my MIL sprayed hers with Malathion. I didn't and lost the plant. I should have, because Malathion isn't that bad when it comes to insecticides. It was quite the epidemic around here a couple of years ago. A lot of people lost their hibiscus plants.

I am full of contradictions today.

Good luck with your plant, taz.

I had the same thing early this spring. They shouldn't kill the plant, but they will keep it from flowering. I sprayed them a few times a day with a hose, making sure to blast them all off, and some insectisidal soap will surely help.

FYI, I've tried all sorts of soaps, hot pepper mixes, everything. The ONLY thing that has consistently worked for me (AND it even kills Japanese Beetles in a matter of a few minutes) is diluted Dr. Bronners in my sprayer. Seriously, one little blast and the beetles (aphids, what have you) just drop.

Huh. That sounds perfect... no Dr. Bronner's here, though, sadly. Wah!

Chop/smash some garlic and let it steep in water for a while, until it's good and smelly. Strain it into a spray bottle. Add 2 or 3 drops of dish soap (but make sure it's NOT anti-bacterial). Spray infected leaves. For good measure, rub the leaves between your finger and thumb so that you smash the aphids. Bingo -- aphidicide.

I say, take off and nuke them from orbit, it's the only way to be sure.