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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:

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  • Why do the flies on the mums bother you?
    – Stephie ♦
    Oct 31, 2015 at 17:27
  • Chances are good the "flies" also include beneficial wasps and other members of the ecosystem.
    – kevinskio ♦
    Oct 31, 2015 at 18:13
  • @kevinsky No, they're common house flies and maybe a few flesh flies (I don't know why the latter are on the flowers I think they just hang out from the nearby trash cans and who knows what else).
    – Jason C
    Oct 31, 2015 at 20:06
  • Are the plants outside or inside? Are they planted in the ground (if outdoors) or are they in containers - if they're in containers, what potting medium was used? Lastly, are the plants in full sun, and do you have other flowering plants which the flies are not interested in?
    – Bamboo
    Nov 1, 2015 at 15:21
  • @Bamboo Outside. Potted. Unsure what they are potted in. Full direct sun all day. No other flowers. There are 12 pots. The flies all arrived suddenly a few days ago and seem to have evicted the bees.
    – Jason C
    Nov 1, 2015 at 16:38

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I don't think there's much you can do to reduce the presence of the flies (bluebottle type by the look of it). They do pollinate plants to a degree, and they prefer strong smelling plants, particularly those in full sun, and especially at this time of year, in fall, just before winter, when temperatures are falling. What's important is whether they only congregate on the flowers, or whether they're attracted to the soil or just the area where the pots are generally. They may just be sticking to sunlit areas, but there may also be something in the potting medium that's attracting them, like bonemeal does.

Any treatments you use will also affect bees and hoverflies, unfortunately. If its not something in the potting medium, then its the flowers themselves, and the fact they're in full sun.

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  • Oh well. Thanks. They are exclusively on the flowers, mostly in the centers, and generally uninterested in the soil. They are not as bad on cloudy days. Will sadly probably have to just get rid of the plants if the flies don't calm down soon. The flies around here do tend to carry strange things with them and like to bite. The flowers look so nice, too. :(
    – Jason C
    Nov 1, 2015 at 16:53
  • I'm guessing were it summer, and you had other or different plants in flower, there wouldn't be an issue with the flies - they stick to cooler shady areas when the temperatures are higher. what a pity...
    – Bamboo
    Nov 1, 2015 at 17:05
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    I agree with bamboo, but here is a link to site where you can build a wasp trap that doesn't catch bees. However, I see a fly in the picture of the dead wasps, so it might also catch flies and not bees. completegarden.wordpress.com/2008/09/11/… Also, a carnivorous plant mixed in might help as well.
    – Dalton
    Nov 2, 2015 at 15:56
  • You could also try a carrion flower like Stapelia gigantea. I had one for a while and it definitely drew the flies. The aroma isn't too strong. Unfortunately, they aren't frost hardy. Also, not sure when they flower and for how long.
    – Tim Nevins
    Aug 15, 2018 at 20:37

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