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Since a while we have a problem with those little flies, which generally are present near the plants (or flying along your ears when you are reading or working on the computer). As I do not want to use any spray, because I don't expect it to be sustainable, but just killing them one by one does not seem a solution. I've tried for a while, but I feel each time they become faster (maybe natural selection of the fastest?). Before we had some fruit flies, which were easy as you just had to make sure to keep garbage closed and fruits to be covered.

What are they? And what can I do against them?

Additional information: The 'flies' are about 3-4 mm long and I'm living in Belgium.

They seem to be gnats (or fungus gnats), someone knows its name in Dutch?

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  • They are probably fruit flies. Have you tried Hedgeballs?
    – user141
    May 28, 2013 at 16:45
  • Some time ago we had fruit flies, but they were thicker, had bigger eyes and also seemed a little bit larger. Those even do not show any interest for fruits. I don't know a lot about fruit flies, so I might be wrong.
    – Sironsse
    May 28, 2013 at 17:05
  • @Chad I had a look on that Hedge balls. I had never heard about it and it might be a solution! I'll have a look at an organic shop because otherwise I have no idea where to get them.
    – Sironsse
    May 28, 2013 at 17:17
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    To take a step back, killing flying insects (with anything) isn't really sustainable. If they're not spreading disease (which would impact the standard human-centric definition of sustainability), then let them be. They're food for birds. Birds also eat berries and spread seeds, and are extremely valuable. Etc., etc. You're certainly free to kill them if you like, but I just don't want you to think that finding a non-toxic solution is actually sustainable. Sorry to be a buzzkill.
    – Nate
    May 31, 2013 at 9:24
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    You're so right! I adore insects, and I'm always very welcoming to my insect friends and spiders are like my pets.. But there is a limit when they start to make big families on a place where I have to work and concentrate. I told them to go out, but they don't listen to me! The only solution left is a genocide! I'm sorry.
    – Sironsse
    May 31, 2013 at 11:02

5 Answers 5

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There are many types of gnats like fungal gnat, fruit flies, etc. How exactly you can get rid of gnats may depend on which plant it is (if the plant needs a lot of water or not). Remove the top layer of the soil, because gnats generally lay their eggs on the top layer. Take the plants outside, use a shovel and remove about one inch of the soil's top layer. If necessary, place new soil in the pot.

First try removing any food sources they have been feeding from. This would include removing any fruit left out on counters. Any houseplants should be ideally planted in containers that can drain since gnats also love wet, standing water on top of soil. Your plant’s soil should be moist but not overwatered.

Some gnats can develop due to excessive moisture so be careful not to over-water the plants.

I read some articles on the internet from which I got some nice solutions that fit here.

Read more: How to Get Rid of Gnats in House Plants

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They are gnats, and breed in plant soil, sink drains, and any moisture anywhere!

Put some bleach down your sink drains, be vigilant about moisture (water under the dish drainer, all those places you never think about).

As to the plants, I had to put mine outside for a week and stir the top of the soil with a fork every day, and no, sprays do not work on these guys.

I also have birds, and the buggies were laying eggs in their water dishes. More vigilance!

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    Thanks for the confirmation that they are gnats! And thanks for the recommendations. Now I have two problems. One: I have no terrace or anything to put my plants outside. Two: Bleach is very aggressive and I guess it might be not ideal for the environment?
    – Sironsse
    May 30, 2013 at 4:27
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I agree with the suggestions of Yadav and Kat, though I had a similar looking bug that turned out not be gnats (though this was in the US, so I'm sure we have some different bugs) In any case, if your plants can tolerate a small drought, letting the soil dry out as long as possible (especially if you can put them in direct sunlight for a while) helped take care of most of them for me. Then I went ahead a removed the top layer of soil, like someone suggested above, and they were basically gone.

I don't know if it was related, but I also started washing my fruit a vegetables right when I bought it, instead of right before I ate it, just to be sure there weren't any eggs I was letting hatch.

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Here is a method that works for Indonesian sand flies.

  1. Tear a plastic bag to get 2 sheets of plastic

  2. Dip them in any oily substance (to make it sticky).

  3. Attach them next to an outdoor light

  4. Re-oil the plastic every week

One of this trap easily kills hundreds of monsters each night. By setting 4 similar traps we reduced the (very) local population by about 90% in matter of days.

Too bad it doesn't work for mosquitoes. And it looks ugly.

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They are called "Sørgemyg" in Danish (http://plante-doktor.dk/soergemyg.htm). I have them as well. Nematodes kill their larvae in the ground. There is a Danish website that sells the nematodes: http://www.nyttedyr.dk/produkt/nematoder-mod-soergemyg.aspx That site says it is possible to catch the adult flies with yellow, sticky papertraps as well.

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