Flies on spirea bush

Asked July 25, 2016, 8:09 PM EDT

In the last week of so, we've noticed a huge number of flies hanging out on our spirea bush. (GROSS!) We've never had this before and thought maybe there was a dead bird or something, but we've not seemed to find anything that's attracting them. This evening our neighbor mentioned that he's had a ton of flies on his raspberry bush. Sadly, he threw away the raspberries thinking they were bad or something. Any info/advice you can give would be much appreciated. Thanks in advance!

Ramsey County Minnesota flies horticulture

1 Response

Insects in quantity - even beneficial insects - can be disturbing to people. The flies are likely blow flies. You may be are seeing a higher than normal population due to weather conditions and timing of hatching. Take heart - flies are important pollinators and do not necessarily indicate carrion is nearby (though they are attracted to dead creatures too). You will see the population decrease as they move through their short lifecycle.

Raspberries may also be visited by the above flies, but also by the spotted winged Drosophila (SWD). SWD is a type of fruit fly that lays its eggs in soft fruits like raspberries, blueberries, and grapes. It is a known invasive pest and should be reported to the MN Dept. of Agriculture. Identification can be confirmed by capturing these pests in a homemade trap. More information about the SWD can be found here : http://www.extension.umn.edu/garden/insects/find/spotted-wing-drosophila-in-home-gardens/index.html