Aphids

Question

How can I be sure that I have aphids and not some other critter?

Answer 1

They will look like small dots, typically on the back of the leaves of the plant, but it can be on the stems too. I like neem oil for treating aphids. These articles will help you:
https://www.gardeningknowhow.com/plant-problems/pests/homemade-aphid-control-a-natural-way-to-kill-aphids.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm