We tried this and it works!
Aphids reproduce faster than any insect on the planet. When the weather is warm, many species of aphids can develop from newborn nymph to reproducing adult in seven to eight days. Because each adult aphid can produce up to 80 offspring in a matter of a week, aphid populations can increase with great speed.
Aphids can cause stunted growth with curled or distorted leaves and drastically weaken a plant. They excrete a sticky honeydew on which black sooty molds can grow, and the white cast skins of aphids can accumulate on the upper surface of leaves.
Aphids do have natural enemies, including other insects, insect larvae, and birds, but these are typically not enough to handle an infestation because of how quickly aphids multiply.
One method we've been testing to kill off an aphid infestation is consistent use of an orange peel spray. Boil two oranges worth of orange peels in a cup or two of water for ten minutes, let it sit for 24 hours, and then strain the liquid into a spray bottle. The hot water helps to release the natural oils in the orange peels.
Orange peels contain a natural insecticide called D-Limonene that will repels a number of insects including fruit flies and whiteflies in addition to aphids. The smell of citrus puts them off.
Spray the entire plant, taking care to spray thoroughly under every leaf where aphids love to congregate, and also stems and tops of leaves. Give a spray to unaffected plants next to the affected plants while you're at it, to keep them safe from acquiring an infestation of their own.
The key is to spray this every 3 days to kill the bugs and keep them away.
This spray can be used on any plants that have pests, including indoor plants.