May 9, 2011 – Confusing Little Flies
QUESTION:
I service a restaurant that has a recent problem with fruit flies and gnats. I’ve placed scented glue boards for fruit flies but I have not trapped any and the problem is getting worse. Any ideas?
ANSWER:
My first thought would be to verify the identity of these flies. Fruit flies (Drosophila) are very similar in appearance to Phorid flies, but quite different in habits and potential sources. Both have similar orange-brown coloring and are the same size, but a couple of distinctive differences are these. Phorid flies do not have the red eyes of typical Drosophila, although the “Dark Eyed Fruit Fly” is a Drosophila that also does not have red eyes. Phorid flies also have the curious and annoying habit of landing on a surface and then running quickly on it for a moment.
Both kinds of flies could be breeding in fermenting materials such as spoiled fruits or vegetables or spills of juices that have been left and are fermenting and sticky. An interesting source for MANY fruit flies in one restaurant was some discarded beer bottles with lime sections stuck in them that had fallen under some counters and been overlooked. Over a few weeks these two bottles delivered thousands of Drosophila into the restaurant. Phorid flies may like this stuff too, but they also breed heavily in other decaying organic materials, so a very thorough inspection of this restaurant is in order to determine just where the flies are originating. We can place UV light traps and other fly traps to “monitor” for the flies, but these devices are rarely going to “eliminate” the flies if the breeding source remains in place. I’d suggest capturing a few of the flies and making that positive ID so that you know for sure what possible breeding sites to look for.
Then, take a flashlight and plenty of time and inspect every hidden place within this restaurant as part of your Sanitation Inspection – this is a good idea regardless of the pest, and your findings all should be written down on a physical Sanitation Inspection Report and shared with the customer. This allows both of you to discuss the contributing conditions you found that could encourage not only flies, but also ants and roaches and maybe rodents. I don’t know of any traps specific for phorid flies, but UV lights traps catch them readily, so placing some of these in various areas of the restaurant might give you a trail back to the source of the problem. One source that has occurred many times within structures turns out to be beneath slabs where plumbing has broken and all that contaminated water has flowed under the slab to provide Phorid Fly Heaven as a breeding site.
Pest QuestionsMay 11, 2011
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