Is there a pesticide or other method that can be used to keep flies off of flowers (or kill the flies) but that won't harm bees?
I am in the northeastern US, dense urban area; the flowers are Chrysanthemums, outside, full direct sun, potted, not sure what they are potted in. No other types of flowers around. Flies are mostly house flies and at least two other varieties (blue bottle and flesh), bee species unknown mixed. Flies seem interested only in flowers, mostly the centers but sometimes the petals, not very interested in soil, and they don't hang out on the ground or walls or anywhere else nearby (except by the trash about 20 feet away).
Building is mixed zone residential and commercial. Flies are already an issue with trash but prior to placement of flowers they were at least confined to trash area. There is a day care on premises as well and the flies give it a "dirty" unprofessional feel, and the health department does not want flies around either. There are usually about 20-30 flies on the flowers at any given time, which enter the building and also swarm with foot traffic, general nuisance. The bees generally ignore humans and are pleasant to have around and help out the flowers, and there's only about 2-4 at any given time (but the flies seem to have pushed them out).
Here is one: