I've had aphid problems in the past, had them on a few pepper plants in my greenhouse this year, I find that a good neem oil spray takes care of them most of the time, just spray either early in the morning or late at night just so that the wet oil doesn't cause burning on the plant from the sun. Check daily and spray as needed, if it doesn't kill them all it'll at least keep their numbers down. Keep your eyes open for ant activity, the little bastards farm aphids like cows and will move them to better feeding grounds. Thats how I got them in my greenhouse, if you see alot of ants on a plant chances are there is a "herd" of aphids under a leaf.
My nightmare this year was spider mites, they were everywhere this year I had them on my nasturtiums, moon flowers, black eyed susan vines, and butterfly peas. They even somehow got into my greenhouse, and now I have to check and watch all the plants I'm bringing indoors like a hawk because if even one gets in it'll reproduce and move to the other plants.