Hi - we have had drain flies for about 2 years. We finally got a plumber with a camera and saw a crack from our kitchen sink under our slab. We have had the pipes replaced but still are seeing these drain flies.

Question is.. since we did not remove the contaminated soil (didn't know we had to) and then put a concrete patio in, it is impossible to remove the soil. Will these flies ever die off? Since there is no new drain water leaking in the soil, will this ever be controlled?

Thanks!

Yes, you can get rid of them. It'll take time. The soil will have to dry past their survivability level. You can help by stressing the population with granular soil insecticides around the slabs and in the expansion joints.

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Originally Posted by ddinenna

Will these flies ever die off? Since there is no new drain water leaking in the soil, will this ever be controlled?

Thanks!!

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Hi! ddinenna, and welcome to AMHD :)

If the soil would have been replaced, it still may have taken several months before you stopped noticing them.
With the original soil still there, it could take years.

See Management on this link:
Cornell Entomology at Ithaca - Drain Flies or Moth Flies

If you really want to get rid of these flies, what I'd do is drill holes through the new patio on either side of the replaced drain pipe, run tubing into the holes, into the soil below.
Apply a pesticide using the tubing or just pour it directly in.
With the tubing though you can apply pressure to give you better coverage.

After the flies are gone, repair the holes with matching Cment. I doubt if your guests would notice, If you don't point them out.

You probably could find pros to do this for you.

K

KUXJ,

I've not heard of that treatment for anything besides termites, how effective is it for other soil dwellers? Millipedes, Beetle grubs, and occasionally earwigs become a problem in this area; will that work on them as well?

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Originally Posted by Catsmine

KUXJ,

I've not heard of that treatment for anything besides termites, how effective is it for other soil dwellers? Millipedes, Beetle grubs, and occasionally earwigs become a problem in this area; will that work on them as well?

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As with termites. As long as you can be within a logical range of the perpetrator, and use the proper pesticide under pressure, it is very effective.
The tools for application would be the same as for termites, just a different 'cide.

There are three items though, that are working against ddinenna.

• The exact route of the drain pipe. They might want to re-employ the use of the plumber.
  Unless he remembers, he'll need to use ground penetrating radar/sonar.
  I'd even let him drill the holes. Liability issue. ;)
• The new patio. For some homeowners, to damage a new addition would be catastrophic.
  (That's why I added to your rep...Longer, but less stress)
  Though an experienced mason or a very careful homeowner could affect a proper repair.
• ddinenna may not be able to obtain the proper pesticide, unless he/she is licensed.

The question ddinenna needs to ask is... "Which is worse, the disease or the cure?"

Thanks everyone - we actually found out our old bathroom vent and behind our tub has access to the soil were the leak was. Now... what kind of chemical should I use to put in the soil? Liquid, powder or should I get terminix or some professional bug guy. Do you think Home Depot sells anything that could work.

Calcium carbonate would be your best bet.

Home Depot may carry it in the Garden section; ask them for lime dust. What you'll be doing is changing the pH of the soil. You'll want a lot.