that could be aphids.
the reason i say Spinosad is that it's about the safest pesticide i know of, as far as humans are concerned. they culture it now, but it was a naturally occurring bacteria in an abandoned rum factory in the Caribbean somewhere. it's pretty much nerve agent for insects, harmless to humans, and has a short half life, it's gone in 3 or 4 days.
Home Depot recently started carrying it, and you can get it off of Amazon, as well. i recommend the quart of concentrate, at 1 TBSP per quart of spray, it makes a lot, and is a lot more economical than the premade spray. Captain Jack's dead bug brew is the brand i've been using, but i imagine they're all about the same.
another thing i like about it is it's safe for bees as long as it has a chance to dry, so if you use it outside, do it in the early evening, when the bees have gone to the hive for the day