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Jude's avatar

Follow-up to my house gnat question (details inside)

Asked by Jude (32190points) May 3rd, 2011

I am having a terrible time with tiny flying house gnats. They are hanging around my plants. Last Winter, I brought in a bag of potting soil that had been sitting out in my Dad’s backyard. I used to the soil to top off one of my indoor plants. Bad move, as with this bag came some nasty gnats.

I tried a couple of home remedies (suggested by jellies and some that I found online); adding cinnamon to the soil, adding dish soap to some water and soaking the plants with it, having a container of vinegar (attract gnats) and dish soap (trap the gnats) near the plants. None of these things work.

The gnats are getting worse and I would really love to keep my indoor plants. The gnats are getting into my dog’s water dish and are hanging out all along my front window. I need to bring out the big guns (chemicals). Suggestions?

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17 Answers

ANef_is_Enuf's avatar

My dad had the same problem last year, really bad infestation. He also keeps a lot of plants in the kitchen. Truth be told, he solved the problem with classic flypaper.

syz's avatar

I’m treating our plants with a product called gnatrol ( a non toxic substance, a bacterium that affects the larval form and is specific to the gnats), as well as putting up sticky traps (don’t waste your money on the yellow ones sold specifically for gnats, I’ve gotten a gazillion more gnats on the fly traps than I have on the gnat traps). We also use a minimally toxic spray, but while it’s satisfying to kill the visible little buggers, it’s seems to be a bit of spitting in the wind. I haven’t noticed that the cinnamon has done anything besides make a veterinary lobby smell oddly like a bakery.

All of these efforts has resulted in a much reduced (but not eliminated) population.

creative1's avatar

My step father is an exterminator and he had given me before a poison to mix with water and use on my house plants when I had a similar issue, they were dead in no time. I would suggest talking to your local exterminator if you are looking for a poison, as over the counter isn’t as strong or effective.

Jude's avatar

@syz Did you purchase it online? I checked out a site that was offering it, and apparently this item has been discontinued by the manufacturer and is no longer offered

syz's avatar

Well, damn, I don’t seem to able to post a functioning link, but amazon has it in stock.


Here ya go

Jude's avatar

@syz The link is not working for me.

cheebdragon's avatar

I hate indoor plants. The only way I know how to get rid of them is to move the plants outside…
But if you want to kill a bunch of them, set a glass or bowl of red wine out for a couple of hours and they will all find it.

Adirondackwannabe's avatar

I think there’s an organic control that’s very effective but I’m drawing a blank on trying to remember it. I’ll look it up tonight. I hate using poisons, especially around pets or kids.

Jude's avatar

@Adirondackwannabe If/when you remember, please let me know! :)

JLeslie's avatar

Bomb the place with those spray pestcide thingies. Make sure no gas is open and no pilot lights are on.

snowberry's avatar

Well I have had gnat problems for over a year now. They destroyed one of my plants, but the others have survived, so far. I am the one who suggested cinnamon, and at the time I was as thrilled as you to see someone had a “cure”, but I didn’t even have any cinnamon in the house, so I had to buy some first. Well I have it now, and here you say it does not work. (Sigh)

There is another gnat control product out there, and it IS available, although I have been to lazy or too disorganized to buy it. It is only available over the internet as far as I know. Here is the place to order it.

Here is more information about it and precautions. It sounds much less toxic than many other options out there. Whatever else you use, it also sounds like it would be helpful to get sticky traps (I would think white is best because the brighter it s, the more they are attracted to it) that you can put in the windows. They are attracted to the light.

snowberry's avatar

Oh, and I’m thinking I’ll have to sterilize any potting soil I use (even the bagged stuff from the store) from here on in. Oh fun!

Adirondackwannabe's avatar

@Jude First line of defense is yellow sticky traps. They’re squares on stakes you put in the plants and the gnats love them for some reason. If that doesn’t get rid of most of the gnats try pyrethrins, but make sure it’s the organic variety and not one of the synthetics. The organic variety breaks down quicker and is less toxic.

Jude's avatar

Thanks, my friend!

Jude's avatar

They seem to be hanging around the one tropical plant with the crappy soil. I have decided to get rid of the plant. I have separated it from the others (removed it from my apartment) and now I’m no longer seeing gnats.

snowberry's avatar

That does not mean they are gone. It means they have laid eggs in the soil of the remaining plants, and are either in the larvae or pupae stage. Get ready for new generations.

snowberry's avatar

I’ve learned a lot about fungus gnats since my last post. If you have soil infested with fungus gnats, just let the soil dry out, and they’re dead. If they’re in your plants, try to keep the top of the soil as dry as possible, and they’ll also die out. This is because the fungus gnats larvae must migrate to the surface of the soil before they can emerge as adult gnats. Allowing the soil to dry out between waterings ensures they can’t get to the surface, and thus can’t mate.

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