Terrible phorid fly infestation. Need advice!


Old 05-13-19, 07:44 AM
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Terrible phorid fly infestation. Need advice!

We've been battling phorid flies in our house for quite some time. We had a good exterminator come out before it got cold out in the winter, and we thought we had it nailed. However, as soon as it started warming up, they reappeared. We are not positive of where they're coming from. The largest concentration of them have been in the kitchen and the upstairs bathroom. We were told it could be a plumbing problem or something else. But we don't have any plumbing back ups.

This is what we've already done:

-Put drain gel down the bathroom and kitchen drains for a few weeks.
-Put tape over all bathroom drains and kitchen drain to see if they are coming up through the drains. We didn't see a single one.
-Sealed off and taped kitchen window to see if they were coming through there, as we have mulch and soil outside under the window. Not a single one came through the windows from the outside.
-Put tape over the air vents. We did have some flies stuck on the back side of the tape in the vent under the kitchen cabinet, and a couple on the back side of the tape on the living room floor vent.

So, the little bit of evidence we have makes it seem like they are in the duct system. Would having the ducts cleaned get rid of them? Could it be something else we're not thinking of? We don't have a ton of extra money to have people come in and attempt to figure it out, but still have the infestation.

Any experience or thoughts would be greatly appreciated!
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Old 05-13-19, 11:19 AM
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"Put tape over all bathroom drains and kitchen drain to see if they are coming up through the drains. We didn't see a single one."
Just to clarify, "We didn't see a single one" means that they weren't on the tape but still business as normal in the living spaces? I'm pretty sure that's what it means, just want to be positive, thanks.

Proper ID of flies is important to solving the problem and it sounds like you've got a good ID on these guys, as well as you've done good inspection and testing.

I doubt they are living in the air ducts as that would be a too dry environment, unless there is something decomposing in a duct but you'd smell that for sure.

They may be getting drawn into return ducts and distributed through the supply ducts, somehow getting around the filter.

They may be entering the ducts through the floor/wall vents as they may be attracted to that dark environment for harborage so that when you taped the vents shut, they were already in there, giving the appearance that they came from there. So it's possible that the ducts have nothing to do with the flies except for the coincidental appearance of them.

Is there an attic that may have a "run" of ductwork to inspect? Attic ductwork can be compromised by chewing rodents, rodent dies and when decomposing nearby there will be flies.

Do you have central air conditioning? If so, where does the AC condensate drain to? Floor drain, condensate pump, or sometimes simply into a hole drilled in basement slab which would be a "red flag" for me. I've seen and experienced myself that the condensate pump can have mold/fungus in it which could be a conducive condition.

Did you try taping around the base of the toilet(s)? If the wax ring/seal that goes from base of toilet into the sewage pipe dries out and shrinks, then that seal is compromised. I've seen this happen.

Sometimes phorid flies can come from slowly leaking cans of food deep in a pantry too. Don't see this much anymore as cans are made so much better but we've gotta keep this as possible. Also rotting potatoes will cause fly problems too. It was not unusual to find a paper bag of potatoes that had been placed behind other stored products and forgotten about until flies showed up.
Old 05-13-19, 06:32 PM
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We are not positive of where they're coming from
That is so important - we had a fly infestation in the neighborhood about 15 years ago that was so bad there's no way I could explain it without you thinking I was exaggerating. The cause for use was a septic pumping company emptying into a field a few blocks away. Stopping them stopped the flies.
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