fungus gnats in worm bin

slegoSeptember 12, 2005

Hi. I've had a worm bin for about 6 months now. It's a very basic rubbermaid container type of bin with shredded newspaper bedding that stays in my basement. It has ventilation holes in the sides, but none on the bottom (until this morning).

Previously, I had a white mite infestation that got better when I began adding dry shredded newpaper along with the food.

Now, however, I believe I have a fungus gnat infestation and it's unpleasant. The little critters can fly and walk and they don't have red eyes (which is why I don't believe that they are fruit flies although they are fruit fly size). I believe there are also fungus gnat larvae in the bin (tiny, skinny white worms). The flies/gnats are not just in the bin --they're in the basement too-- but I know they are coming from the bin.

I have fly paper hanging in the bin and near the window where they congregate after they leave the bin. I have gone so far as to try to vacuum out the bin (and I've gotten a bunch of the critters this way, but of course not all).

I just put some very small drainage holes into the bin in the hope that this might help dry it out just a bit.

The worms are as happy as they could be and are totally oblivious to all the activity going on around them.

I'm afraid my husband, who had been very tolerant of having worms live in the house, might reconsider if the gnat problem dosn't improve.

Any suggestions would be appreciated.



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hinzy(z5 PA)

I had, what I think, is a similar problem.
I used Knock-Out Gnats from Gardens alive it contains BT
(Bacillus thuringiensis (Bt/H-14).
Followed the directions and in a few weeks they
were gone.

Good Luck,

Here is a link that might be useful: Knock-Out Gnats

    Bookmark   September 13, 2005 at 5:59AM
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Thanks for the suggestion, Jim. The BT won't hurt the worms?

Also, I read somewhere about beneficial nematodes being useful for dealing with the larval stage of similar insects. Any idea if this would work for fungus gnats?


    Bookmark   September 13, 2005 at 10:30AM
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try using a "no pest strip". Google image it for an idea
of what it looks like.

    Bookmark   September 13, 2005 at 12:43PM
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newbie314(Z9 CA)

If these are like the flies I had, look like small black fruitflies with no red-eyes. Kind of easy to kill when the land, then what I used was a trap.

Small yogurt container, some watermelon (pulverised) in it, then placed in a small zip lock sandwich bag. I then cut a small hole in one corner and then pressed the corner into the container (like a lobster trap). They love it and eventually go in.

___ ____
I \ / I
I v I

Also found the flies get in by crawling on the side of bin into the food. I try to line newspaper flat against the bin wall. This stop a lot of travel

    Bookmark   September 13, 2005 at 1:08PM
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Yes, the description sounds right. They're easy to catch/kill with scotch tape when they're resting on the wall or ceiling. They seem to like to hang out together as pairs.

I think I have too many gnats and larvae to try the trapping with watermelon idea---next time if/when they first appear I'll try that. I like the idea of a piece of newspaper to stop travel and I'll try that.

This might be a silly question, but with regard to the no-pest strip, do you put the strip in the bin or outside? (I have plenty of gnats outside too, but zillions inside the bin). It looks like the strip has some kind of insecticide in it, so I wouldn't want it killing off the worms.


    Bookmark   September 13, 2005 at 8:04PM
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It doesn't harm the worms.

    Bookmark   September 13, 2005 at 10:09PM
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hinzy(z5 PA)

Tonytone00 is right, it doesnt harm the worms.
I've also used the yellow sticky traps from gardens alive.
Good luck!
Last year I had them bad...took a few months to get rid of them all.

    Bookmark   September 14, 2005 at 1:34AM
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Thanks for the suggestions! I bought the no pest strip, but it looks pretty toxic, so I just ordered Bt from Gardens Alive. We'll see what happens...I always have the no pest strip as a back-up.

    Bookmark   September 15, 2005 at 11:20AM
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newbie314(Z9 CA)

The yogurt container trap really worked for me. I must have had 50 within the first week.

I just keep putting water in it to keep it moist.
Looks a little gross with the fungi but man it really dropped my population down. Seem like when one goes in they all start to follow. Maybe they set up bacteria cultures in the trap. They never really went to another trap even with the same stuff in it.

If you are digging around a lot in the bin I find this causes problems. They have time to enter, and the new adults have time to escape. Even going away for two weeks didn't help, not until I covered the sides. Making the paper wet helped stick it to the side as well as adding more paper.

    Bookmark   September 15, 2005 at 12:30PM
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bendback50(8 B/CS-TX)

You might also try microwaving your feed stock until it bubbles before adding it to the bin - freezing for 3 days accomplishes the same thing.

It won't kill the existing gnats but once they are gone you wouldn't be introducing new eggs/larva to the bin via veggi peels

just a thought


    Bookmark   September 15, 2005 at 10:48PM
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I have been scrupulous about freezing the food scraps because I REALLY didn't want to have to deal with fruit flies. So, instead of fruit flies I got fungus gnats. I'm hoping that, after I get rid of the exisitng ones and all their larvae, the new drainage holes I have in the bin will keep it a little drier and less attractive to gnats.

    Bookmark   September 16, 2005 at 1:10PM
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newbie314(Z9 CA)

Make the traps :-). Try any juice, just make sure you touch it so fungus grows. This explains why the don't go for the fresh traps. The trap is funky and they like it.

They don't seem to like the colour yellow very much.

I find they go in the traps at night.

I originally went on vacation for 2weeks without opening the bin, and I still had the gnat issue.
Now I see maybe 1 or 2 a day. They seem to follow me :-). I wonder what that says about my hygiene :-O. Run away...

    Bookmark   September 16, 2005 at 3:41PM
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Runner53(Zone 5 / NW IL)

It sounds like you are all on the same track I am on, though our problem has been more with Fungus Gnats swarming on windows and doors from outside the house. Never-the-less, the problem is the same: Fungus Gnats breed in highly organic, moist soil. The adults don't really do anything harmful, but the larvae can chew on plant roots, if there are any available to chew on... In your case, the attack is on the worm bin. In our case, it is on the Patio Tomato Planters that I set up this year. The BT treatment should work, as would beneficial nematodes. For the adults, any of the pyrethrin or resrethrin type sprays will work.

I have found lots of info on the Web to help in the Gnat fight. I have included a good link from Texas A&M.

That's it for now...I have to get back to my anti-Gnat mission.

Here is a link that might be useful: Texas A&M Info on Fungus Gnats

    Bookmark   October 4, 2005 at 9:36PM
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thanks for that Texas A&M link. it's got some useful information.

Ok, its been about a month since I first posted my request for help, so here's an update on my bin and fungus gnat problem:

-the BEST thing I did came from a suggestion from a non-worming friend who suggested mosquito netting. So, I made an "envelope" out of a 4'x6' piece of mosquito netting--I just folded it in half and sewed up the sides, put the whole bin inside and tied the top shut. That way, while I 'm doing battle with the fungus gnats, noone else in the house is bothered by the little critters. Plus, I KNOW the gnats didn't come in with the food--they must have been visiting my basement and happened upon the very inviting habitat of my worm bin and decided to take up residence. This way, the mosquito netting keeps gnats that are outside the bin, out (while it keeps the ones that are already in,in).

-I put fairly big drainage holes in the bottom of the bin, since I think most of my issues with the worms have come from it being too wet.

-I'm using BT--(Knock out gnats from Gardens alive). It kills the larvae. It says you need to do 3 applications, each a week apart. I'm on application #4 and I still have some adults, but it's much better than before.(I had had a really bad infestation). Since you have to drench the bin with the BT, the drainage holes are REALLY important.

-I add lots of dry shredded newpaper each time I do a treatment. It helps get rid of some of the extra moisture in the bin. I take out the old wet newspaper and replace it with dry paper each time I open the bin.Since its so wet in there, I do have little white mites, but they're not too bad.

-I made stick traps out of old toilet paper rolls and white (or yellow) fly paper (not the super sticky stuff, that's too messy, but the moderately sticky stuff that comes on a long roll.) I cut the tubes in half and staple 2 together to make a nice solid base, thhn I wrap them with the sticky paper. I put a couple ot these on the top of the lid of the bin (outside the bin, but inside the mosquito netting). They catch a fair number of gnats and let me monitor my success in the gnat-war.

-I'm messing with the worms less. This is a bit of a bummer, since I liked frequently checking on their progress, but with the mosquito netting in place, spontaneous visits are a little more difficult. But the worms are happy, happy, happy. Very busy munching large quantities of food.

-I'm willing to do one more BT treatment, and then I'm going to pull out the big guns. I have a no pest strip that I really don't want to use, since its so toxic, but I will if I still have adults after the next treatment.

-when I feed the worms or do a BT treatment, I use a small vacuum to suck up fungus gnat stragglers. It's a pretty rewarding sport.

Ok, that's probably more than ANY of you wanted to know, but I thought since you were all so good about providing suggestions, you needed to know the current status.

Have a good weekend!

    Bookmark   October 14, 2005 at 2:10PM
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I dont know if this would work for fungus gnats but for regular gnats(if there is such a thing) a friend of mine sets out a cup of vinegar with 2-3 drops of dish soap in it. they are attracted to the vinegar and drown. Maybe that would help also.....

just a thought


    Bookmark   October 15, 2005 at 3:21PM
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Southernwood(z6 NJ)

I got fungus gnats in my house plants that spread to my worm bin this spring. Then I somehow picked up a new mite in my wormbin - a very active brown one, much more active than the others I have - and I haven't had a problem with the gnats since.

I have seen insect-larva-eating mites advertised as biological controls on various insects; I think I must have somehow picked one of these types up by fortuitious accident. (They eat decaying matter when they can't get fresh insect flesh. They don't seem to harm worms.)

Unfortunately, if you don't pick them up by accident, I think they cost $30 or $40 (US) to buy.

    Bookmark   October 19, 2005 at 12:33AM
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emily_ak(z2 AK)

I've read that, in addition to moisture and organic matter, fungus gnats are attracted to slightly acidic conditions. I save egg shells, let them dry, and pulverize them in a plastic bag with a rolling pin, and them sprinkle them in the worm bin. Try not to sprinkle them directly on a worm--it dries the poor little guys out. I either sprinkle the dried shells over the whole surface and spray it lightly with a mister or else mix it in with wet worm food. The calcium carbonate in the egg shells will help to raise the pH of the worm bin and make it less acidic, but won't make the bin too alkaline either. As a bonus, worms apparently need calcium to breed, so you will help to ensure lots of little worms in your bin!

    Bookmark   October 27, 2005 at 4:08PM
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Victory!!! I'm fungus gnat free. The BT really did the trick (tho' I needed 5 applications, not 3). I'm keeping the bin in my mosquito netting "envelope" so no more interlopers make it into the bin. thanks for all your help and suggestions!

    Bookmark   November 9, 2005 at 3:08PM
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