Do you know what pest is covering cowpea in picture? It doesn't appear to be eating cowpea, but seems to be going away on wash. It appears to be slowing down growth of cowpea.
Thanks, above suggestion seems to be helping. I am washing it away for now.
Appears to be Aphids.
You can wash away with water and use Neem Oil.
Neem Oil is organic and is safe for people, pets and bees.
Here are some links for you.