Yeah, aphids. You don't have to give up on the pyretherin yet, do successive applications. If you do want to find/try some Neem oil, (it has done VERY well for me) I pasted part of a post from someone who suggested it to me awhile ago-
Neem Oil.
Get some BioNEEM and follow the directions- specifically about spraying UNDER the leaves. Also, use very cold water in the mix. Spray Spray SPRAY. Spray again. Then spray it again tomorrow, then again the next day. Then in about another week (even if you don't see signs of the bastards) do it again about three days in a row- that will kill off the hatchlings when they come out, if there are any. The trick is to do it more than once- if you just do it one time it will not work. You have to repeatedly harass the bastards until they realize it ain't worth the trouble.
I recently recovered from a full on attack by spider mites and neem oil did the trick. If the plant is in a planter you can also wrap the planter up in a trash bag and fill a five gallon bucket full of COLD water with the proper neem oil mix and dunk the plant in it. Then the next day do it again. Regardless of what bug is macking on the plant a solid neem oil bath will cure them right up. I did this to two plants that would fit in a bucket and it worked great and the plants were no worse for wear- definitely no worse than being the friggin' daily dinner for the little bastards.