How to kill aphids?
Soapy water, spray on leaves
Many insects eat aphids, and releasing these natural enemies of aphids into your yard or garden will help to kill aphids. Lacewings and lady bugs, or lady beetles, are among the insects that kill aphids.
Spray aphid-affected plants with the insecticidal soap-water mixture either in early morning or late afternoon, when the sun is not at its peak. Ensure that you spray enough of the solution to wet all the plant surfaces, including the leaves' undersides.
Spray them off with a strong spray of water or scrape them off and squish.
Try a soapy water spray
Neem oil works really well. Follow the directions about applying.
A botanist I follow recommends using Dr Bronners to make a soap spray. A few squirts of Dr Bronners castile soap in a spray bottle of water and spray on the underside of the leaves.