hey sri, as i was at my local library today studying various topics it hit me that my original response to your question may not have been completetly accurate.
for those aphids that attack peppers, they don't care which pepper plant they attack other than they stay close to where they were born until they run out of food or something scares them off.
however, there are those aphids that do focus on just one type of plant like the black cherry aphid....but i didn't think this was your question and didn't think you were being bothered by black cherry aphids.
aphids are complexed, though a simple creature, they don't come in a one size fits all bug. some lay eggs, some bare their young live and some do just focus on one type of plant, the ones the target peppers also look to tomatoes and other green foliage to feed on.
the aphids i have, in my house, travel from my italian parsley, peppers, goji berry and some other flowering plants i have(can't remember what they are called) and they don't touch my easter cactus. the information i provided before should only be followed with container plants and a few outdoor garden plants because any more than that, then you lose control of the ability to target the aphids. All my plants are in 1 gallon containers and readily easy for me to address and control.
i do have a sapping type tree in my yard, that in some summers produces extreme aphid populations, that i do spray with just plain water to knock them out of the tree. last year, for whatever reason i had very few aphids in the tree. the year before(2009) i couldn't walk in the grass under he tree as it was so sticky with aphid juice. i actually took out a pail of soapy water and a hard brissell broom and had to scrub the grass. at the same time, my ant population went crazy as did my ladybugs. often, i would pick up ladybug larvae and move them to my pepper plants. you have to remember that my pepper plants, for the most part are brought inside in the evening due to the cold. i have several totes that i fill with like minded pepper plants and just carry them from my deck into my house in the evening.
for outdoor plants, depending on how many you have, would get up early and manually squish as many as i could. then i would spray them will a botanical insecticide. one product i have uses Pyrethrin daisy extract as its fighting agent. does it work.. somewhat. i found some aphids on my dwc plants early this morning so after squishing the visible aphids, i gave the plants a dose of this juice. 4 hours later i return to find more aphids, that just moved from their hiding spots to the outter leaf.......ya....i squished them too. tonight, they seem to be aphid free, in this case i have no soil to remove and any that fall into the nutrient resavoir become nutrient.
hope that helps and i hope i didn't confuse you as i thought about it all day.
) a year after that i started to have aphids very season! but this time i think they have reduced in numbers of plants they attack and kept away from my pepper plants. last attack was last year on my seedlings.