The best solution I have found for keeping bees and wasps away from hummingbird feeders is mint extract of some sort. After I wash the feeders, and before I fill them, I take a Q-tip, dip it in the extract, and apply it to the ports. I also apply to the edge where the bottle comes in contact with the bottom, and, if applicable, along the seal created when putting top and bottoms together.
This simple solution worked the first time I used it and has worked ever since. Using extracts can be costly. My tiny bottle lasted for over three years, and yes, it froze during the winter months.
I haven't tried rubbing fresh mint leaves to the ports, etc., but I am sure this would also work.
Source: I cannot recall exactly where online I found this solution. Perhaps hummingbird(s).net
By leeanne collins from Clio, MI