How can I prevent drain flies from infesting my deck and yard?




We have had an infestation of drain flies the past two years, but only when it’s warm (IL). I’ve been fighting them inside and searching for a source. Today I found a bunch outside under a low (3ft clearance) deck. It’s always moist under there as it gets no sun. Any tips on keeping it dry or at least discouraging the bugs? I had some river rock, but the sloped earth makes them slide out away from the house.Thanks!Neil
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They are definitely drain flies, they end up around sinks and occasionally we’ll see larvae near drains. I have an idea how to contain them inside with drain enzymatic cleaner, but can’t get rid of them. I’m thinking this moist area under my deck might be the main source that I have not tackled.
This is what the flies look exactly like:
https://images.app.goo.gl/ZQriEqEUPGHKyYAH9
Try covering the slope under the deck with a waterproof tarp. It will keep the area dry AND covered. Make sure you tack the edges with garden staples or something else to keep it from shifting and sliding away from the house. If you have power available, a box fan can also help dry it out after it rains. Hope that helps.
I would dry out the area under the deck, then use Rustoleum's Never Wet 2-part treatment . That should help the water bead and evaporate quicker. Then address the drain by using some borax pour down the drain.