Plant or place potted onions and related plants next to plants where you want to repel aphids. Wild onion and garlic thrive and propagate the easiest. The scent of chive or shallot also repels aphids.
Make an onion spray for aphid-infested plants if you prefer not to grow actual onions. To make a spray, chop onions into small pieces and place in a blender with 1 quart of water for each onion. Strain the solution through cheesecloth, and transfer it to a spray bottle or garden sprayer.
Spray large areas of affected crops with the solution from a garden sprayer. Use a spray bottle to spray individual plants.