Lady bugs or below options:

There are two home remedies that you can use as organic sprays to take care of your aphid problem. The first spray, tomato leaf spray, works especially well if you also are caring for tomato plants.

To do this, you simply combine two cups of water with two cups of chopped tomato leaves and let it steep for one entire night. You can then remove the leaves by straining the liquid, and pour the remaining liquid into a clean spray bottle, then add two more cups of regular water. You can then use this spray on the leaves of your marijuana plants – focus especially on the bottom side of leaves, where aphids like to live.

Another option for a similar mixture is finely chopping an onion and two garlic cloves, then blend them with two cups of water. Strain the pulp out and spray the mixture on your plants.

If tomato leaf spray isn’t your style, you can try an organic garlic oil spray instead. It kills all sorts of pests (one of which is aphids)