If you put wasp repellent on a hummingbird feeder will it also repel the humming birds?

It would be best if it did, because anything that repels insects may be dangerous to hummingbirds (would you spray DEET on your dinner plate?).

You can reduce problems with wasps by making sure your feeder doesn't leak and wiping any spilled sugar water off the outside of it every time you clean and refill it. If you do this and wasps are still a problem, buy a yellowjacket trap at a hardware store or home improvement center, fill it halfway with sugar water, and hang it where your feeder usually hangs. The wasps that would have been hanging around your feeder will climb in and drown. When you stop seeing wasps visiting the trap, you can rehang your feeder in that spot.