Little black gnat type bugs

earthlydelights(6 pushing 7)January 21, 2007

i can't say for sure where these came from, other than a houseplant, but they seem to be multiplying.

i'd like to spray or something, but don't want to the hurt the plants or pets or people.

any suggestions on what i can use to get rid of them in one fell swoop?



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Small, black flying bugs near a house plant usually mean Fungus Gnats and the hatch in soils that are too wet. Start by checking your potted plants soil to be sure it is not too wet. Inserting you index finger to the first knuckle, soil should be dry that deep before watering, will tell you how wet that soil is.
To control Fungus Gnats start by putting some yellow sticky traps (yellow poster paper smeared with a sticky substance works well) around to trap the adults. alloowing the soil to dry out will help eliminate the larva although pieces of mosquito dunks (Bacillius thuringiensis - Isrealeanis) can help a really bad infestation. Some places would suggest Diazonon (no onger available I hope), carparyl, methoxalor, etc. but these very toxic poisons are not needed, especially in your house in winter.

    Bookmark   January 22, 2007 at 6:55AM
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rhizo_1 (North AL) zone 7

Maryanne, there is no one fell swoop. You'll need to take a look at the moisture problem, as has been mentioned, but fungus gnats can thrive if your soil is just too peaty. If the infestation gets too bad, it's sometimes necessary to repot with a new, improved mix.

But anyway, you should address the moisture issue! Some people say that it is most helpful to add a layer of coarse sand to the surface of the containers, making it difficult for the adults to lay eggs. Diatomaceous Earth, in food or horticultural grade, will also help a great deal.

The dunks that were spoken of is one method of applying the Bacillus spores to the soil. They must be dissolved in the water that you use to drench your plants (on watering day). The other method of applying Bt is to purchase Gnatrol, a product made expressly for this purpose. Bt solutions must be applied for several weeks for all of the generations to be killed. If you cannot get control of the problem by the above mentioned methods, you may need to resort to Bt. It is absolutely safe to use in the home, and around people and pets.

Diazinon is no longer available, and I have no idea what those other chemicals are...I think kimmsr made them up (lol)! Regardless, you should never bring chemicals into the home environment, and have no idea why they were even mentioned.

    Bookmark   January 22, 2007 at 10:44AM
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morz8(Washington Coast Z8b)

Maryanne, Gardens Alive carrys a product called Knock Out Gnats that is the same safe BTi as Gnatrol - very effective on gnats. It takes about three consecutive applications to stop the breeding cycle, applied on your regular watering schedule.

They have a couple of online specials going right now (and most of the time :)) - one for free shipping and one for a $25 discount.

Keycode Free Shipping: 144138 (ends tomorrow)
$25 off $50 order -Offer Keycode: 144019 (ends Mar 7)

    Bookmark   January 22, 2007 at 12:00PM
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earthlydelights(6 pushing 7)

thank you all for the information. i'm off to garden's alive to order. i hung up a few of those fly strips that i find in the hardware store. the poster board sounds good, i can attach that to the door.

i have checked all the plants and cannot even tell which one it is coming from, but the problem certainly hasn't been eliminated. they are always in the room, next to where i have the plants and come around the computer. i've learned to keep my teacup or glass covered as they can land in there too.

it's a little colder than normal in the upstairs room where i have my plants, so i've been real careful about watering, because i always have a thought that the water will be too cold and kill the plants. none of them are drenched, but i'm off to check them all out to make sure.

this is a first for me and these things are annoying. i appreciate the hlep.

    Bookmark   January 22, 2007 at 2:03PM
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morz8(Washington Coast Z8b)

Maryanne, I'd never seen the gnats until bringing home a new prayer plant from the hardware store.

If anything, my plants (some 20+ years old) are a little neglected, not overwatered. I wonder if the 'overwatering' isn't 'overstressed' sometimes when it comes to diagnosing the reason for an outbreak of gnats.

What's dumb is, I noticed the little fly guys when buying the plant, but didn't realize how obnoxious they could be or that they would invade every plant in every room of my house. The BTi took care of them, and I've never had them again. Indoors that is. I have found them in seed flats outdoors so I keep the Knock Out Gnats on hand - the larvae are said to also feed on fine roots, not good for seedlings.

    Bookmark   January 22, 2007 at 2:56PM
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rhizo_1 (North AL) zone 7

morz8, you've hit the nail on the head about the watering. Judging just by what I've read just here in the gardenweb over the years, the problem is obviously more complicated than over watering. I think that one infested plant can bring them in (as you've observed), or bag of potting medium that has been exposed to fungus gnats elsewhere.

Add that to potting mediums that are too fine textured and don't drain very rapidly, and you've got yourself a nice little FG nursery!

    Bookmark   January 22, 2007 at 4:15PM
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Usually the best solutions to problems are the simplest. This article from Ohio State University may answer many questions about Fungus Gnats.

Here is a link that might be useful: OSU on Fungus Gnats

    Bookmark   January 23, 2007 at 6:59AM
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earthlydelights(6 pushing 7)

thanks again for all the information. i did order the gnat away from gardens alive and then of course after i placed the order, i found a spray, kind of what i wanted in the beginning, but i stuck with the GA order.

i'm wondering if it had anything to do with the fact that i transferred over to about 90% of my pots being terra cotta? in any event, i hope to get this under control. wish i had been more diligent in the beginning, probably could have avoided all of this nonsense.

thanks again

    Bookmark   January 23, 2007 at 12:00PM
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Loretta NJ Z6

Terracotta has nothing to do with it. If anything, those pots dry out faster than plastic.

My friend tells me she has had success this year with her small seedlings using this method. She removes the plant from the pot along with the soil from the roots. She then microwaves the soil and replaces the plants in the same soil. So far, she's happy. Sounds messy but I may try it.

    Bookmark   February 5, 2007 at 1:05PM
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Loretta NJ Z6

I don't know if it is a good idea to recommend people to microwave their soil, BTW. Are there any metals that would affect the microwave?

    Bookmark   February 5, 2007 at 1:09PM
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earthlydelights(6 pushing 7)

i don't know that i can give my seal of approval since i've been using this knock out gnat and still have these bugs. i also have those yellow sticky things here, there and everywhere and there's enough of them on each of the papers.

this is horrible. this was brand new potting soil and not the cheap stuff either. i guess there were some eggs in it because i don't know how else you get these things.

i've alreaedy tossed out over 2 dozen plants that i've lost because of them. i am not sure what to do with the soil, so all the pots are sitting outside still full of dirt which i'll trash when the weather is nicer.

if it was spring, this would be simple enough to take each plant outside, trash the dirt, wash the roots and start from scratch.

this is all a first for me and it's so disappointing. guess i was due.

any other suggestions??????

    Bookmark   February 5, 2007 at 7:34PM
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jean001(z8aPortland, OR)

Other sorts of fungus gnats exist beyond the kind that infest overly wet potting mix.

Those other critters can multiply in other wet sites -- a wet mop, a wet garden/landscape, in the drain pan under the fridge, and more. Look around for other possible wet sites and/or materials. Then fix the reason the excess moisture/water is present.

    Bookmark   February 5, 2007 at 8:17PM
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Loretta NJ Z6

How long did you use the product? It doesn't kill the adults like a bug spray. The larvae are suppose to eat the Bt and those are killed. The adults live for 7 days according to the diagram on the GA page. During that time, they can lay more eggs. So you need to make the applications according to directions in order to catch successive generations during the larva stage - three weekly applications.
Anyway, I've never used the product and can't say whether or not it works. I am just going by your posting dates and by that, it was too early to declare defeat - unless your plants were dead.

When fighting fungus gnats, you might consider yourself successful if you reduce your population as you go instead of completely getting rid of them all at once.

    Bookmark   February 6, 2007 at 3:50PM
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Try putting out a small cup half filled with cider vinegar or cheap beer to drown the adults.

    Bookmark   February 25, 2007 at 1:07AM
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morz8(Washington Coast Z8b)

Maryanne, are you making any headway on your gnats?

All I have to offer is the suggestion of patience (the BT in Knock Out Gnats does work) and my sympathy -

I repotted several young citrus a couple of weeks ago, also in a high end commercial potting mix, and I've got gnats now too. It's been at least 5 years since I've seen a gnat :(

I started with the BT treatment yesterday; they should be gone by St Patrick's Day....there's really no way to rush the cure. The citrus are kept in this room and the gnats seem to be attracted to computer monitors too - I'll just try not to spill my coffee in the mornings as I grab at them as they flit by :)

    Bookmark   February 25, 2007 at 11:38AM
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jean001(z8aPortland, OR)

It was said: "Try putting out a small cup half filled with cider vinegar or cheap beer to drown the adults."

That trick works for fruit flies but not for fungus gnats.

    Bookmark   February 25, 2007 at 2:54PM
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I was going to say, cider vinegar DOES NOT work with fungus gnats.

I saw this suggestion online and tried it. All is looks like is we have half full glasses of urine around the house. The gnats ignore it.

Oh well. I ordered the BT.

Mary in Virginia

    Bookmark   January 30, 2008 at 5:17PM
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I am getting these gnats in my bathroom. I got rid of a plant I had several weeks ago (it was in bad shape & I had a feeling that was what was causing the gnat problem), but I am still getting the gnats - can anyone suggest how I can get rid of them?

    Bookmark   March 11, 2008 at 10:15PM
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I have had great success using water and dish detergent. I take water and use a good dose of soap, I then saturate the soil of each plant. I have had good success with this method, it is the combination of soap and water. When I can find Ivory soap flakes I will use that instead of dish detergent. The Ivory soap flakes and water can be used in a sprayer as well.

    Bookmark   May 9, 2008 at 3:45PM
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morz8(Washington Coast Z8b)

queenie, if you have them in your bathroom and no longer have plants in there, you could be dealing with drain flies and not gnats

    Bookmark   May 9, 2008 at 9:01PM
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The problem with most control measures is you need to add product using more water, and wet conditions were a major contributor to start with! :( If you have new seedlings or tender rooted starts, letting the soil dry out might not be wise in all cases. If you are looking for a quick kill, mixing 1 part of 3% hydrogen peroxide (the kind in most retail stores) with 4 parts of water will kill them. Spinosad will kill them. As will BT. I can't speak to the effectiveness, but apparently a stick of Cinnamon and/or a little tea bag in a gal of water overnight that you use for regular watering will kill or deter them. Cinnamon, purportedly kills the mold/fungus that attracts the gnats, but I am not sure if that is how it works. I have used hydrogen peroxide, and it works. But as with BT or Spinosad it may take several applications.

    Bookmark   November 24, 2012 at 1:05PM
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