I was thinking about using vinegar, diluted in a spray bottle to get rid of them. Would that be a good idea, ie would it work? I have used the "spray them hard with a hose nozzle, just wash them off" approach and yes it works, but it gets rid of most not all of them.
These are collard greens. I'd like to give them to a relative in Sebastopol who is originally from the South. I can hardly give them collard greens that are mostly clean, but some have aphids. Not all the plants have aphids. And the lettuce doesn't have aphids. They seem to like the collard greens.