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Getting Rid of Fruit Flies and Fungus Gnats

There is no doubt that one of the MOST frustrating things about vermicomposting (and the thing I’m convinced is one of the real limiting factors preventing much more widespread interest in this field) is the other “critters” that can take over our vermicomposting systems. A couple of the worst offenders are undoubtedly fruit flies and fungus gnats.

I am definitely an advocate for “ecosystem rights” in a lot of ways (haha) – and really try to hammer home the point that a vermicomposting system is NOT just about the worms – BUT, I don’t have a whole lot of sympathy for the plight of these pesky flying varmints. Unlike with many of the other organisms that can pop up, such as mites, springtails, and white worms, it’s easy (for me) to think of fruit flies and gnats as “invaders” – we certainly DON’T need them involved in the process, and I certainly don’t need clouds of them up my nose!
:lol:

Well, it just so happens that I have a fairly healthy population of both of these guys at the moment, so I’ve decided to have some fun (at their expense – MOOOHOOOHAHAHAHAHA!!). I placed an order for some parasitic nematodes (Steinernema feltiae), and set up a couple of fruit fly & gnat farms (pictured above) I hope to turn into nematode rearing cultures. As some of you will recall, I have tested S. feltiae before (see “Steinernema feltiae – Fungus Gnat Killer“) and I actually found them to be quite effective – at least initially. The issue is that the effectiveness seems to decline over time – undoubtedly due to the fact that the nematodes end up getting killed. For one thing, I discovered that scientific research has shown that the passage of these nematodes through an earthworm’s digestive system kills them (see “Steinernema feltiae and Red Worms“). I’m sure there’s also a fair bit of competition/antagonism due to the wide assortment of other organisms that can live in the rich composting environment.

Aside from wanting to work a bit harder at creating ongoing cultures of these nematodes (thus meaning I can apply them over and over again), I’m also VERY interested in once again testing to see if these nematodes will attack fruit fly larvae as well. I did set up an experiment to test this out last time around (see “Steinernema feltiae VS The Fruit Flies“), but I’m pretty sure conditions (outside during the summer) were too warm for proper testing.


Anyway…I will certainly keep everyone posted on my fun nematode experiments, but if I might shift gears a bit here, I think it’s not a bad idea to spend more time on this “Getting Rid of Fruit Flies and Fungus Gnats” topic in general (especially since a lot of you likely assumed that’s what this post was going to be mainly focused on).

Let me start by saying that both of these guys are a ROYAL pain once they become well-established, but of the two it’s the fungus gnats that are actually the most frustrating (in my experience). Unlike fruit flies, it can be very challenging to remove their “food source” since the larvae will feed happily on a very wide assortment of decomposing materials. You’ll likely need to be a lot more patient and thorough with your eradication efforts. On the plus side, really bad gnat infestations don’t seem to be nearly as common as is the case with fruit flies.

In both cases, PREVENTION should definitely be a very high priority! There are lots of different ways to lessen your chances of getting invaded. Here are some things to consider:

1) Observation – simply keeping your eyes open for any signs of small flying insects in your house is certainly an important part of the process! Fruit flies will likely first make their presence known in the kitchen – especially if you happen to keep fruit out in open bowls etc. Be especially wary of fruit from warmer regions – bananas, pineapples, melons are all regular fruit fly sources, especially if they have any sort of injury/lesion/disease. With fungus gnats you will want to be most careful with any potted plants and soil that you bring into the house since it’s not uncommon for them to already contain larvae and/or eggs. A good rule of thumb with your indoor potted plants is to let them dry out a fair bit between waterings. Constantly moist soil can become a prime gnat breeding ground. Generally, I’d also recommend keeping your worm bins a good distance away from any of your houseplants.

2) Careful Food preparation – This one applies more to fruit flies than fungus gnats. One thing I really recommend, if at all possible, is to freeze all your food scraps prior to adding them to your worm bins – especially in the case of uncooked fruit/veggie waste, and extra-especially (haha) with these materials that have also been sitting out for a period of time (in fruit bowls, scrap holders etc etc). Freezing these wastes will actually have a two-fold advantage. The obvious benefit will be the killing of any fruit fly eggs/larvae that happen to be in the material. Secondly, freezing can be a valuable way to start the break-down process (water expands when it freezes so this tends to rupture cell walls etc) thus making it easier for microbes to invade. You might want to let the materials thaw before adding them to your system though, since a lot of water can be released plus you don’t want to shock the system with a rapid temperature drop (could be helpful if your system is overheating though). Apart from freezing wastes, I also recommend chopping up (or even blending) materials before adding them since this will make them a lot more microbe- and worm-friendly, lessening the chances of other organisms gaining a strong foot-hold. On a related note, just generally feeding in moderation can go a long way towards avoiding any critter population explosions.

3) Physical barriers – I highly recommend always keeping a really nice thick layer of bedding materials up above your main composting zone. While this certainly won’t completely stop fruit flies and gnats from getting down below to lay their eggs, it CAN at least be a deterrent. It can also help to mask any odors that can attract these insects. Of course, having lots of bedding in your bin can also just generally be a great way to maintain a healthy environment, since it soaks up excess moisture, provides more worm habitat, increases air flow, and helps to balance the rich food wastes being added. You also may want to cover up your air holes with some sort of fine screening material, or even enclose the entire system in a big mesh (think mosquito netting) bag – perhaps a little extreme, but at least your chances of ending up with an invasion will be greatly reduced.


I think it’s safe to say that you should expect to be invaded by one or the other of these flying varmints at some point during your vermicomposting journey (or more realistically, BOTH of them – many times over! haha), so let’s now talk about different ways to deal with them once they become established!

When I’m not my usual mellow, laid back self (or otherwise engaged in various experimental pest breeding programs – haha), I like to employ a multi-pronged approach when attempting to get rid of gnats and fruit flies. Here are some of my suggestions:

1) Traps – various types of traps can serve as reasonably effective passive methods for capturing flying adults. They can also serve as valuable early warning indicators if you set them up before you get invaded. A very easy fruit fly trap can be made by putting a small amount of apple cider vinegar (or wine vinegar etc) in a jar with a tiny drop of dish detergent (reduces surface tension) and then covering the opening with plastic wrap before punching some small holes. Fruit flies will crawl through the holes and drown in the vinegar. Interestingly enough, I’ve discovered that these traps can also catch a fair number of fungus gnats as well – so I highly recommend setting some up either way.
Another type of trap that seems to work well for gnats is a sticky trap – especially one that’s positioned close to a light source. I’m not sure why, but gnats seem to be much more attracted to light than fruit flies, and even brightly colored sticky traps seem to draw them in. Some of you may recall my experiment with fly paper (hanging near a light bulb), and just how effective it ended up being for attracting gnats and bigger biting flies (see “Fly Paper – A Must-Have Vermicomposting Tool“).

2) Vacuum Cleaner – I’m sure this one will cause some snickering among those uninitiated in the ways of the the fly ninja assassin! (haha)
Joking aside, this is a phenomenal way to rapidly reduce the population of adult “breeders”, and thus greatly reduce the number of eggs being laid in your system. I highly recommend doing this at least once a day for best results. Aside from literally opening up your bin with vacuum nozzle in hand, also make an effort to round up as many of the roamers (those flying around your house) as possible. Again, a nearby light source will likely be a good place to start when hunting fungus gnats, and you may find a herd of fruit flies gathered around your fruit bowl or food scrap holder (speaking of which, you may want to throw scraps straight into the freezer once you have fruit flies in the house, since they will quickly make these containers a prime-time breeding ground if you don’t). It’s also pretty easy to make a powerful fruit fly attracting system (similar to the fruit fly farm shown above). Simply add a bunch of fruit scraps to a large plastic water/juice/pop bottle, along with some bedding materials (so it doesn’t get too sloppy and foul in there), then create a LOT of tiny holes using a pin or something similar. The idea is to allow odors out, while preventing fruit flies from getting in (although, it’s unlikely they’ll get back out even if they DO manage to squeeze in somehow). Fruit flies will congregate on or near this system and you should be able to vacuum up a lot more of them all at once as a result.

3) Remove Excess Food | Stop Feeding – As mentioned earlier, this is going to be a much more effective strategy for fruit flies than for fungus gnats, since gnat larvae don’t rely upon food wastes for their sustenance to the extent that fruit fly larvae do. Nevertheless, this is still a recommended approach for gnat invasions as well since every little bit helps. Feel free to continue adding bedding materials though – this can help to keep your worms alive without helping out the gnats and flies.

4) Let the system dry out a fair bit – This one will be especially helpful with fungus gnats, but should also help with fruit flies as well. The larvae of these pests thrive in wet waste materials and tend to be a fair amount more sensitive to drying than even the worms themselves. Not everyone will likely want to go this route, however, since it will more than likely require that you leave the lid off of your system for quite awhile (obviously resulting in more gnats and fruit flies being able to escape into your home) – but you might use it as a final step in the process, once the population of adults is clearly on the decline.


Ok – well, that basically covers some of my primary ways of dealing with these pests. Obviously various forms of biological control could be included in that list as well, but really the only promising option I’ve come across thus far is the use of parasitic nematodes – and again, I still need to test out this approach a lot more before I can provide a solid assessment (stay tuned)!

One last important thing to mention – most of what I’m suggesting here is intended for those with indoor systems. Unfortunately with outdoor systems there really isn’t a whole lot you can do to prevent either of them (well ok – you won’t likely end up with fruit flies if you aren’t using any sort of fruit/veggie waste), or get rid of them once they are established. I don’t personally find them nearly as frustrating in outdoor systems (not quite so “in your face” I guess), so perhaps this isn’t really a big deal anyway – but figured it was worth pointing out.


I am VERY interested to learn what approaches others have found to be successful for preventing and/or getting rid of fruit flies and fungus gnats – I’m sure there are plenty of effective methods not mentioned here. It would be really cool if we could turn this post into a sort of “ultimate” resource for dealing with these annoying pests.

Please share your ideas and methods below!
8)

Written by Bentley on October 17th, 2011 with 59 comments.
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Get your own gravatar by visiting gravatar.com EVP
#1. October 17th, 2011, at 6:09 PM.

We had a gnat problem because one of our teachers put pineapple rinds atop the shredded newspapers we use as bedding. I just brought my worm habitat outdoors (far from the building) and released the fruit flies into the wild. Then I returned the habitat indoors and made sure we always have a nice thick layer of newspapers on top. We haven’t had re-infestation for over 2.5 years.

Get your own gravatar by visiting gravatar.com Steve K
#2. October 17th, 2011, at 6:25 PM.

Hey Bentley,

Once again, this is a well-timed and popular topic, and I am glad that we are revisiting it. As it turns out, I have had a major fruit fly outbreak this past week, due in part to my sloppiness in not freezing some peaches before adding them to the Worm Inn, but also becuase my worm population is a lot smaller since I moved my systems across state lines last this summer. Now, we have FF’s in the house, and the wife is not amused.

The approach so far has been to use vinegar traps, as you suggested. I have also tried the go-to solution of adding more bedding and have completely stopped adding food to this system. In addition, I take the system (a Worm Inn) outside once a day and open it up to let the adults fly out, in an effort of reduce breeding. The only thing I can think of to add to what you’ve said above is that the vinegar traps seem to lose effectiveness after a day or two. I wonder if the flies can detect their dead bretheren in the trap. Any ideas?

Otherwise, moving the worms went very well. I gave away about 25% of my worms to a friend, then gave away about 60% of the vermicompost to a local organic gardener and combined the worms from both of my indoor systems into one bin and left it at my very understanding in-laws’ place for a month while we resettled. After it was all said and done, the worm population had self-regulated and got quite a bit smaller, but is once again thriving. If anyone is interested in more detail, I can provide a writeup.

Get your own gravatar by visiting gravatar.com margie
#3. October 17th, 2011, at 6:35 PM.

since we moved the worm dudes into the basement to get away from excessive heat and ants outside we discovered that our resident spiders(we named one Boris and let it go at that) started feasting on the fruit flies and have had no problems since then–a couple of years now–

Get your own gravatar by visiting gravatar.com Linda
#4. October 17th, 2011, at 7:13 PM.

I have used a mixture of 1 cup SC vinager, 1 cup suger, cook on stove till sugar had dissolved, and pour over a banana peel inside the jar. I use a milk jug, swirling the mixture alittle, and hang it in my barn, or place above my worm bins. Both fruit flies and the nat’s are drawn to the sugery mix, but something in the bananan peel chemisty, mixed with vinager, will kill them. You will see layer after layer of dead kritters in your jug. When full, replace cap and throw the whole thing away. I used it in my rabbit barn, and when we use to raise beef cows, hanging it fron the barn roof inside. Outside, its good for bees and hornets.

Get your own gravatar by visiting gravatar.com Alyssa
#5. October 17th, 2011, at 7:33 PM.

I have had great success with a thick layer of dry bedding followed by enough procesed compost (use a worm inn so I take it right out out of the bottom and throw it in top) to seal the layer. This works great with FF and house flies.

You can also order praying mantis eggs. I havent tried this yet with the worms, but I had a houseplant aphid infestation once and our mantis cleaned house. Plus, they are super cool!

Get your own gravatar by visiting gravatar.com jay
#6. October 17th, 2011, at 7:51 PM.

I just vaccumed up a bunch yesterday and put newspaper on top of one bin..the other bin is not affected at all. I feed them both equal of what I have. I did try putting a spider in there a couple weeks ago, I don’t see him though. The better half has vinegar traps upstairs to try and catch them. If I don’t see a reduction in number, I think she will have me shacking up with the worms.

Get your own gravatar by visiting gravatar.com Cathy Geary
#7. October 17th, 2011, at 7:59 PM.

fungus gnats turned into a huge problem for me, more than just in the worm bin. They came out of the worm bin and laid eggs in my 800 + el- derberry cuttings that I had rooting in the basement under lights and before I could identify the problem, killed about 75% of them. The quick solution to stop the damage was to crumble up mosquito donuts, made of BTi, which is organically approved. However, I am not certain if it will damage the worms, so did not put it in the worm bin. Through carelessness I killed off a large percentage of my worms this summer. A large storm blew through and blew the lid off the bin and it rained in it during the night and I had a veritable lake the next morning. Poured off all the standing water – don’t know why the drain holes were not functioning. Anyway, still have living worms but it will take till next summer to fully recover. I guess I’d better remember to order the beneficial nematodes early this coming spring.

Get your own gravatar by visiting gravatar.com Lee in Iowa
#8. October 17th, 2011, at 8:06 PM.

I had both dratted buggers come in on some peaches I had left on my kitchen counter to ripen a bit more. I tried several things, but then one evening (ahem), I set the dregs of a glass of wine near my stovetop, where a nightlight is always on. In the morning, presto! Drowned flying pests! (The later generations have been smarter and not thrown themselves clear into the liquid, so I’m going to use some bad wine in a trap like the one Linda suggests, in comment #4.)

I’ve tried the vacuum cleaner before, and it helps but doesn’t stop the invasion. For my bins, I now use a huge layer of lightweight shredded paper, which helps around my bins. It’s upstairs in the kitchen, where I start stockpiling leftover teabags and such that I am having flying teensy pest problems. For now, Linda’s idea and plain old flypaper (remove thumbtack and warm for 10-15 seconds in microwave for pain-free, no-hassle unrolling) are working best.

Oh, and those fungus gnats? If you put a 1/2 cup of vinegar down any nearby drains every evening, you can really inhibit them. That’s one of their best secret hiding places–in your nasty drain traps.

Get your own gravatar by visiting gravatar.com Carolyn
#9. October 17th, 2011, at 8:43 PM.

1. Cover system with sheer curtain like material.
2. Cover top of system with mostly finished vermicompost.
3. The fruit flys prefer $$$ wine :-)
Add a drop of dishwashing liquid to the dregs.
A plastic cover with holes in does not seem to improve the catch.
Put the cup on top of a bit of a column.
This seems to attract them.
If glass is used, holding it up to the light will show the days catch.
Very satisfying.

Get your own gravatar by visiting gravatar.com Mark from Kansas
#10. October 17th, 2011, at 8:47 PM.

I can only recall this happening to my bins once. I freeze my scraps and I generally add feed and water every 7-10 days.
I had housefly maggots once but, after the turned into adults, they flew away.
I have 2 bins in the house and 1 bin in the garage.

Get your own gravatar by visiting gravatar.com Hilary
#11. October 17th, 2011, at 8:58 PM.

I set out a glass of wine with a couple drops of soap added to break the surface tension. Works wonderfully : )

Get your own gravatar by visiting gravatar.com theophile
#12. October 17th, 2011, at 9:45 PM.

I’ve had both fruit flies and gnats, but at the moment I’m relatively clear of both. Fruit flies are pretty easy to catch with the vinegar traps. I’m interested in trying Linda’s vinegar/sugar/banana peel technique for catching gnats.
In the past feeding my worms only newspaper/cardboard for a few weeks has worked to cut down on the gnats. Also, like Lee mentioned, they like your sink drains; now I just keep the stoppers in place overnight.
Also, I also think I’ve gotten some help from the spiders! I don’t like spiders, but we have a non-aggression pact within the area immediately around the bin.

Get your own gravatar by visiting gravatar.com Christine Twombly
#13. October 17th, 2011, at 9:49 PM.

For those who live in an area with cold winters….I had a worm bin in my classroom. When it was infested with fruit flies I would bring it outside when the temperature was below freezing and open it up for just a few minutes. That did the trick.

Get your own gravatar by visiting gravatar.com Kevin Jiang
#14. October 17th, 2011, at 11:07 PM.

Amazingly I have no problems. Looks like my dad’s Earth Machine attractes them all.

Get your own gravatar by visiting gravatar.com Jorie
#15. October 18th, 2011, at 12:22 AM.

I had a pretty bad fruit fly infestation last year around this time which I think was probably caused by not burying food well enough. One morning I opened the lid and a ton of these guys flew out! I took the bins out into the garage for about a month (it was getting to be around 40F at night outside but this helped to slow down the fly population. I figured I might lose some worms, but a month at these temperatures didn’t seem to phase them.

The large fruit fly population running around the house didn’t seem to care for the vinegar traps so I threw some banana peels in a large zip lock bag and left it half open. Twice a day I would carefully seal the bag and then smash the ones trapped in the inside. I would then open the bag up again a crack and proceed to do this again the next day. I would say that by the end of the week, I got almost all of them.

Get your own gravatar by visiting gravatar.com Melody Silverberg
#16. October 18th, 2011, at 1:43 AM.

Had both fruit fly and minute black scavenger flies in an indoor bin. I first tried beneficial nematodes, which really helped lower the number of breeding adults. I have a Worm Factory, and the nematodes love the lowest level where the compost tea collects. I recycle the tea by pouring it over the upper levels, and have seen gradually reducing numbers of flies
over the past couple of months. The nematodes seem to live in the worm castings and tea. I add to the upper levels of the composter because I have noticed the fruit flies and scavenger flies seem to inhabit the upper levels rather than the lower. I assume that is from the nematode activity being higher in the lower levels. I have also added a full bin of oak leaves as suggested by the Worm Factory manufacturers. All in all, a greatly reduce volume of flies, even with me being away from home for 10-14 days at a time. Have not tried freezing or cooking scraps, but have read that this helps, too.

Get your own gravatar by visiting gravatar.com Jil
#17. October 18th, 2011, at 1:50 AM.

We have used apple cider vinegar as well as cooking wine in a shallow dish. Seems the cooking wine was the more favored fluid. We set one in the kitchen and one in the bin. We also started freezing everything then letting it defrost before adding it to the bin. The combination of these tactics controlled the fruit flies and once gone they haven’t been back. Now the freezing technique is all we need to do to maintain a ‘pest’ free worm bin. We recently changed our plastic bin system to the VB24 system and it is wonderful. Works great. the worms are never crawing up sides or wandering.

Get your own gravatar by visiting gravatar.com Amy
#18. October 18th, 2011, at 6:02 AM.

I keep mine covered with a pretty piece of cloth. Haha. Ever since I started keeping it covered up no more gnat problem. I suppose it makes it difficult for them to get in and out. I have a worm factory. Pretty is the real key. It looks much more elegant that way too heheheh

Get your own gravatar by visiting gravatar.com Duff
#19. October 18th, 2011, at 12:16 PM.

I freeze all of my scraps. When I thaw them, I put them in a small bucket and stretch a pair of nylon pantyhose over the top, so the thawing scraps don’t get reinfested with fruit flies.

Get your own gravatar by visiting gravatar.com John vandermyde
#20. October 18th, 2011, at 12:24 PM.

I’ve had great luck using Landscaping Cloth – it’s a spun grey polyester fiber sheet that is sold as a weed block. Great ventilation while keeping even the tiniest mites out. I drape it over the top of the tub, and then secure it with a bungie cord wrapped around the tub under the lip.

I also use a milk jug trap, plus fly paper, sitting on top of the tub right on the landscaping cloth.

Get your own gravatar by visiting gravatar.com rob
#21. October 18th, 2011, at 2:50 PM.

Actually, I have been finding that newspaper bedding over top actually increases the smell factor from my plastic bin, maybe because it cuts down the airflow too much. Thoughts on that?

Agreed on the cheesecloth over top, and traps. A mix of water, cider vinegar, a bit of wine, a dash of honey, and a dropof dish detergent works great. You don’t need plastic wrap on top, because the detergent lowers the water surface tension so much that the bugs sink right in as soon as they land. I even put a shallow dish of that right in my bin and killed the problem at the source.

Get your own gravatar by visiting gravatar.com Holly
#22. October 19th, 2011, at 12:09 PM.

I have actually tried diatomaceous earth with bentonite (clay). I had heard that the DE is very effective at damaging the exoskeleton of all insects and causing them to dehydrate and die. It has no affect on the worms. I’ve only tried it a couple of times and the worms have happily incorporated it into their world. I’ve heard that they actually love the stuff. Seems to have helped a bit but I need to be more vigilant! This method also works on fleas and unfortunately, our friends the spiders.

Get your own gravatar by visiting gravatar.com Bentley
#23. October 19th, 2011, at 1:58 PM.

Wow! Thanks everyone for chiming in! Lots of really good stuff here. I can’t respond directly to everyone unfortunately, but will attempt to address specific questions, and touch on some of the suggestions people have made.

STEVE K – Interesting observation about the vinegar losing effectiveness quickly. I haven’t seen this myself – actually have a pretty foul jar of murky vinegar with countless fruit fly corpses (uggghh) that’s still drawing them in. I almost wonder at times if these older jars can actually become breeding systems though (with the repeated swirling of liquid up on the sides perhaps enough of a film builds up to support larvae?)

LINDA – fascinating recipe! I’ll have to try that one. You are totally right about banana peels. They go absolutely bonkers for them. They seem to have no problems breeding in bananas that are even slight overripe. Pretty sure that’s where a lot of my current population has been coming from.

LEE – great point about the drains for gnats. Can be one of those mysterious, never-ending sources of these guys if you don’t realize where they are coming from! You and others have mentioned wine – again I totally agree here. Seems to be more of an attractant than the cider vinegar. Alas, tis a lot more expensive, not to mention the fact that it helps calm my wife’s frustrations regarding the fruit fly infestation! hahaha

CHRISTINE – Your cold treatment is brilliant! Can’t believe I never thought of that. Definitely a huge difference in cold tolerance between fruit flies and red worms. This fall I noticed that the fruit flies were dying in an outdoor food scrap holder when temps were dipping down overnight (perhaps 40-50 F) – they seem to bounce back, but the eggs are likely a little bit more tolerant.
Now if only I had a walk-in fridge or freezer! lol

——————————
Thanks again everyone! Definitely aim to try this (community) approach with some other popular topics as well.

B

Get your own gravatar by visiting gravatar.com Linda B
#24. October 19th, 2011, at 4:23 PM.

In addition to my hobby of vermicomposting, I run an interior plantscape business-and with that, fungus gnats are an on going problem. I have used diatomaceous earth in plant soil, but wonder if it is truly safe for my worms? Here’s what does work with plants (don’t know of possible harm to worms), Bacillus thuringiensis. You can get these from an insect grower or easier, from a garden store in the form of “Mosquito Dunks”, a product used to kill mosquito larvae in ponds and such. Simply break off a small portion of a dunk (about 1/8 of a disk), dissolve in a half galon of the water to be used for maintaining plant, re-apply about every thirty days. This of course does not affect the “fliers”.

Get your own gravatar by visiting gravatar.com Steve K
#25. October 19th, 2011, at 4:55 PM.

Bentley – I agree that it was strange that the trap seemed to max out at only 6 fruit flies. there were also some small, white solids in the vinegar. I didn’t look closely to see if they were mites, and now I regreat that. Time to replicate the experiment!

In the mean time, I stared a new wine + soap trap. The upside to using wine is exactly as you mentioned. I opened a bottle and made the trap. About 20 min later, my wife asked, “did you open a bottle of wine?” and had a glass. So, maybe it can serve both trap and anti-anxiety purposes at the same time.

Get your own gravatar by visiting gravatar.com Geneviève
#26. October 21st, 2011, at 1:48 PM.

I second the effectiveness of landscaping cloth – it’s great. I use mine as a liner inside my plastic bin. It means I didn’t worry so much about the sizes of the holes that I was drilling in the bin. The cloth never rots, though over years it will shred.

Get your own gravatar by visiting gravatar.com kaleigh
#27. October 21st, 2011, at 3:03 PM.

Do you think that diatomaceous earth would work? Does it hurt the worms?

Get your own gravatar by visiting gravatar.com Carolyn C
#28. October 21st, 2011, at 4:29 PM.

Wow, this post makes me feel so much better. When I first got my worms two summers ago, I immediately had a huge infestation of both flies and gnats that was really distressing- but when I’d search the web for help, the advice I found was mostly “if you have a couple fruit flies, try using a vinegar trap or freezing your scraps or stop feeding for a few days”- fine, but I had SO MANY, and they seemed to be breeding and living in the bedding itself. I tried various vinegar traps and banana peels, plus killing untold numbers of adult flies& gnats that were attracted to the nearby window, but it never seemed to make a dent. In retrospect, my bin was definitely too wet (no drain holes). Maybe I could have left the bin uncovered outside in the sun to help it dry/let the flies free (or would that make it worse/make the worms unhappy? Or maybe I should have transferred them to a new, drained bin. The infestation didn’t die down until summer did (in the winter our apartment’s some 10C, the flies didn’t like it any more than we did.) Anyways, good to know it wasn’t just me.

Get your own gravatar by visiting gravatar.com Michael S
#29. October 25th, 2011, at 1:41 PM.

I had soldier fly larvae show up this year. It’s also my first year vermicomposting. I think I introduced them by adding compost from my leaf compost bin outside. They’re hideous, but good workers.

Get your own gravatar by visiting gravatar.com kevin n
#30. October 25th, 2011, at 4:25 PM.

Wow. We have a very small commercial operation and just brought it inside for the winter. The flies of all kinds were crazy. I took EVERY solution that was given and put it to use right away. Within a day or 2 I had them on the run. Now 5 days later it is very manageable. I will leave sticky traps up alone with bowls of ac vinegar and wine and have a bananna peel jug set up. Truely thanks to all. The shop vac is working full blast. Thanks Kevin

Get your own gravatar by visiting gravatar.com ross benson
#31. October 25th, 2011, at 6:33 PM.

In 2009 I bought a house that had a glass sunroom. I turned it into a green house with vegatables, herbs, and flowers. I installed grow lights and in no time my sunroom and my house were filled with fruitflies and gnats. I used traps of all sorts, and paid an exterminator, but nothing seemed to work. They swarmed me every time I turned on a light, started food preperation, etc.,etc. I got so desperate that I bought an insect control book on the internet. The title is “1001 All-Natural Secrets to Pest Control” by Dr. Myles H. Bader. This is a marvelous book!!! Every gardener, farmer and homeowner should have a copy. Dr. Bader suggest using Oil of Peppermint and Oil of Clove to repel flies as well as other remedies. I went to the local health food store and bought a bottle of these two essential oils. I put a cotton ball on a jar lid and put several drops of both the peppermint and clove oil on the cotton ball. I placed one of these in every room in the house. In three days there were no flies or gnats in the house except for dead ones which were every where. In the sun room it took several weeks before I stopped seeing them. I assume because thats where they were breeding. I found this to be a great remedy. These esential oils are fairly inexpensive and give the area slight but not unpleasant odor for a few days. I replace these every few months and have had no returns.

I highly recommend Dr. Bader’s book for every one. It has remedies for every type of infestation from roaches to rats. Gardeners will love it.

Get your own gravatar by visiting gravatar.com Amy Youngs
#32. October 27th, 2011, at 2:02 AM.

Thanks! Very encouraging to learn that the parasitic nematodes will not kill off the red wigglers. I had been afraid to try them in my vermiponics system before reading your post. My local hydroponics store sells Predator Nematodes (Steinernema carpocapsae & Heterorhabditis heliothedis) I wonder if those will work the same? I can get one million nematodes for $18.

In the meantime I have been using neem oil to keep the fungus gnats at bay. It works well, but if I forget to do it for a few weeks, the buggers come back.

Get your own gravatar by visiting gravatar.com Patsy L
#33. November 2nd, 2011, at 4:51 PM.

I hired an exterminator to take care of a bee swarm inside block wall. He took care of the bees but fruit flies have taken over. There is no way to extract the honey in the block wall. Does anyone have an answer to get rid of thousands of fruit flies?

Get your own gravatar by visiting gravatar.com Bruce W
#34. November 15th, 2011, at 11:00 PM.

Patsy,
Don’t have an answer for the flies in your wall. Ross’ suggestions of oils sounds like a start. If you find a good solution, please post it.

Here is my experience with vinegar & soap traps:

I couldn’t figure out why my vinegar & soap trap wasn’t working until I read one of Bently’s old postings, stating that he had problems with apple-scented soap, which is what I was using. I re-did my traps without my apple-scented soap. Ta-Da… success. Thanks Bently.

I experimented with 3 vinegar traps side-by-side on my kitchen counter, next to the worm food collection bowl. All had about 1 cup of apple cider vinegar & no soap. Here are the results after 1 week:
A) small “deli” cup (2 cups?) covered with plastic wrap and 8 small holes poked in plastic. Too many fruit flies to count. (Hurray!)
B) small plastic water bottle with 8 holes drilled towards the top. Cap was left on the bottle. 8 fruit flies.
C) small plastic water bottle cut off close to the top of the straight sides (before it starts narrowing towards the neck). The top is then inverted & taped to the inside of the bottom section. Flies go down the “funnel”, through the cap opening & can’t find their way back out. 2 fruit flies.

I repeated this with similar results the 2nd time.

Also, I started keeping a deli cup/plastic wrap trap inside my worm bin with good results.

Get your own gravatar by visiting gravatar.com Andrés
#35. November 29th, 2011, at 11:07 AM.

I had a fruit flies infestation, that grew enough to make it unbearable any time I’d open my worm factory.
I have it in the kitchen, since I live in an apartment, and having over 100 fruit flies in there wasn’t really nice.

I tried a couple of things and what worked best was this: I mixed some balsamic vinegar with sugar, some dishwashing liquid and water.
With the fruit flies works like with the worms, surface is the important thing, not deepness. So i took a bowl with the mix in it (you can use the bottom of a plastic water bottle) less than an inch of the mix is enough, but the bigger the surface is, the more flies catches.
Next morning, there were only 4 or 5 flies in the bin, and the bowl was full with the dead flies.
Don’t cover the bowl with a plastic with holes, leave it open, so it will be easier for the flies to go in and die. The lid with the holes is intended for a trap with fruit, in which the flies keep putting eggs in the bait, so they don’t die, they are just trapped inside.

Get your own gravatar by visiting gravatar.com James Marconnet
#36. December 12th, 2011, at 1:51 AM.

Great article and many terrific comments thereto!

My two separate Reds and Night Crawlers worm bins are relatively small and are kept on top of my computer in my office for a little more warmth and hopefully to encourage them to be fruitful and multiply and to grow big and ready for outdoor vermicomposting and fishing bait respectively.

What worm foods have you found that are the least likely to cause problems indoors such as fruit flys, undesirable odors, too much food-composting heating, etc. etc.? Inexpensive or free foods are of course most desirable, but my worms currently eat soooooo little that I’d like to feed them only things with no risk of causing indoor problems.

I know that our fearless leader here is very busy lately, but some of his followers may have their own list of safe foods to share.

Jim

Get your own gravatar by visiting gravatar.com Jamie
#37. March 15th, 2012, at 6:22 PM.

I started some worms in stacks of 5 gallon buckets probably not the best for surface area but easy to maneuver and harvest. I successfully mitigated a fruit fly problem with a varied approach of apple cider vinegar in shallow dishes, flypaper (great stuff!), and microwaving all of my compost for 2.5 minutes. Maybe I’ll switch to freezing in the future. Currently trying to stop a fungus gnat invasion. These are much more difficult. Again, flypaper gets covered but doesn’t stop them at the source. I used a wallpaper steamer to clean the outside of my bins which were crawling with gnats. They like to hide in any little nook or cranny and on the bottom of the buckets so I made sure to steam these areas thoroughly. I’ve also secured lids on bins and moved them outside. I’ll keep you posted.

Get your own gravatar by visiting gravatar.com Michelle
#38. June 7th, 2012, at 1:29 PM.

I work in a pub, and fruit flies can really get out of hand in the warm months (and even for most of the year if they aren’t eradicated).
We tried vinegar traps, but they still preferred the beer taps.

The most effective lure for them has been red wine with a piece of lemon or citrus fruit. Put into a glass with paper rolled into a cone on top (so that there is a tiny entrance hole that they can crawl down into, but once in, can’t get out). tape the paper to the glass so they can’t slip out the sides. In a matter of a day I have caught enough fruit flies to make the glass appear black.

I’d like to try this mixture with the soap. The banana peel bag is very clever as well! Thanks!

Get your own gravatar by visiting gravatar.com Sandie Anne
#39. August 1st, 2012, at 6:11 PM.

HI Bentley,

I’d like to say that I love your website and how you do all your experiments! There is so much great information here.

I haven’t really had a problem with fruit flies in my worm bin. Just a few here and there. I always bury the food scraps.

I have had problems in my kitchen though when I make kefir and let fruit ripen on the counter. Last year we bought fruit fly traps and they work really well. Here is a link to a blog post about getting rid of fruit flies.

Keep up the great work!

Sandie Anne

Get your own gravatar by visiting gravatar.com Sofyen
#40. November 3rd, 2012, at 7:20 AM.

Hi,
After few years of fungus gnat in my vermicompost bin, I finally found the best method to get rid of them. I tryed many things suggested here: traps,drying the bin, starving the worms, parasite nematode, hypoaspis mites, all worked a bit, but never got rid of them once for all, untill recently.
I accidently placed my bin in a location with tiny red ants and small spiders. Surprisingly, the ants were catching them, taking them sometimes alive, and the spiders made nets around the compost bin (and a small lizard started hanging around). The gnats totally disappeared in 2 weeks. The ants even made a nest inside the compost bin.
Unfortunately, I started to panic, afraid that they will attack the worms. I got the ants out, even found the queen and killed it. Slowly the ants disappeared, and the gnats came back. Later, I understood that I found the killer solution for fungus gnats and just stupidly dismissed it, as the red ants will never attack the worms (isn’t it).
I took few photos with an ant walking with his fungus gnat prey I would have posted here, but it seems not possible in the comments. I thaught that you may find this experience useful on red worm composting.

Get your own gravatar by visiting gravatar.com Carol
#41. December 31st, 2012, at 12:16 PM.

I always pot up & bring in some of my plants to overwinter indoors under lights in my basement and inevitably end up with some fungus gnats that move back & forth between the plants & the nearby worm bin, but there are several things I do that helps a lot.
1. Do not overwater your houseplants; the top 1/4″ to 1/2 ” of the soil (or, more properly, soilless mix) should be dry. As everyone knows, the fungus gnats prefer moisture. Keep the top of the worm bedding similarly dry.
2. Ventilation is key. Do not crowd plants, and several times a week I aim a small fan at the shelves to move the air around.
3. I hang yellow sticky traps around, suspended with unbent paper clips and either tape or magnets to hang the traps from the metal of the light fixtures. I make my own traps cutting up pieces of the bright yellow plastic Arm & Hammer liquid laundry detergent containers (cut into whatever size pieces you can get, biggest about 3-4″ square, drill a hole at top for wire) that I then coat with Tree Tanglefoot. Lacking that product (I have fruit trees, so had some anyway) petroleum jelly works just fine & actually is much easier to work with! Since insects are attracted to bright yellow you will get a lot of the adults stuck to the traps and out of circulation.
4. A soil drench of Bt (Israelensis, not the Kurstaki strain, which is for caterpillars) as mentioned earlier gets the larvae that are feeding on stuff in the pots (or bin). Vectobac, Mosquito Dunks, Gnatrol, Bactimos, etc.
Actually, following the above methods and good sanitation in my potting area has meant I never have had to resort to the soil drench.

Get your own gravatar by visiting gravatar.com Teresa
#42. January 22nd, 2013, at 12:14 PM.

I am currently battling a fungus gnat infestation and I have found the above tips very helpful. They have congregated around a window closest to my indoor bin so for the past four days I have been vacuuming daily and opening the window to expose them to the twenty degree weather we are having. This has significantly reduced the number of gnats. I also added a lot of bedding material to dry out my bin as well as a couple of bricks of coconut coir down at the bottom to wick up any moisture that has accumulated. Lastly I laid sheets of newspaper over the top of the shredded bedding to cap it off and thought there are still gnats inside my container there are less flying around the house. Thanks for all the great information.

Get your own gravatar by visiting gravatar.com EARL
#43. April 28th, 2013, at 1:10 AM.

How about a bug zapper over the bin?
When they get zapped they drop in the bin =more BBQ’d worm food.
Also the light will keep crawlers in the bin.
Trying to think outside the box.

Get your own gravatar by visiting gravatar.com Nicole
#44. July 11th, 2013, at 4:50 PM.

Im battling the evil larvae at the moment, I had adults but I put up a sticky fly paper over the stove in the kitchen and that caught 90% of the adults. I am going to try drying the bed and hope that when they turn into adults they will just fly off.

but for adults sticky paper near food works like a charm, if I have guests come over I just take it down =)

Get your own gravatar by visiting gravatar.com ShereeLynn
#45. July 23rd, 2013, at 8:19 PM.

Where can I get some of these nematodes?

Get your own gravatar by visiting gravatar.com Carol
#46. July 23rd, 2013, at 8:45 PM.

There are a number of online retailers that sell beneficial nematodes. Arbico and Gardens Alive are two I know of. They both also sell the Bt soil drench that will control fungus gnats.

Get your own gravatar by visiting gravatar.com Rhonda
#47. August 12th, 2013, at 5:44 PM.

I have a housefly/maggot infestation in my vermicompost bin. I let the adult flies out daily and look for maggots in the bin but can never really see any. I have been looking into beneficial nematodes to add to my bin in hopes this will kill the maggots and flies. Anyone have experience adding beneficial nematodes to a vermicompost bin for a housefly/maggot problem? Any hints, tips, or suggestions? Oh, and I have only been vermicomposting for a little over two weeks and so I am still in the setting up and experimenting stage. I keep my bin covered and have a 2inch thick layer of shredded paper on the top layer but the flies persist.

Get your own gravatar by visiting gravatar.com Sofyen
#48. August 15th, 2013, at 6:04 PM.

Hi Rhonda,
I tried in the past beneficial nematodes, combined with hypoaspis beneficial mite against fungus gnat, it worked sometime, but not for long. It seems that temperature was not ideal for neither mites nor for nematodes.
On the long run, I found that ants are the best pest control for vermicompost bin (see above), as long as you can place it outdoor. Now, I am testing muslin screening for indoor bin. I got flies and gnat, I’ll see what happen.

Get your own gravatar by visiting gravatar.com Carolyn
#49. August 15th, 2013, at 6:34 PM.

Hi Rhonda, I can’t speak to beneficial nematodes, just wanted to share my experience. I had houseflies in a neglected bin although I never saw maggots, and it was gross. I went for my failsafe solution, which is to put the bin outside (protected from sun and rain) with extra cardboard etc. and open the lid a couple of times a day to wave away adult flies. (My air holes are covered with mesh to keep them from returning.) Eventually the problem subsided. Not ideal, but there you are. Maybe get some compost and new scraps to put some of your worms in and try starting a new bin or little hotel (with holes covered, thick bedding on top) in the meantime? My worms weren’t very happy until they had some compost/castings as well as bedding to crawl around in, the first few weeks they weren’t so happy and fruit flies etc went crazy.

Get your own gravatar by visiting gravatar.com Rhonda
#50. August 15th, 2013, at 6:47 PM.

Hello Sofyen,
Thank you for responding to my post :D, it is surprisingly difficult to find information on vermicomposting issues and solution on the internet and especially if the issue includes house fly and maggot issues for some reason. I live in a condo and so I only have a patio space in which I have put the bin already. I have been putting lay flat fly strips (non-toxic, chemical free) in the bin and catching the adult flies that way. Now I have fruit flies and have put a little jar and apple cider vinegar and dish soap that I hope will work. I no longer have the 20 some flies coming out of my bin and instead just one or two as the fly strips seem to catch the majority of them including some of the fruit flies. I went in search of the beneficial nematodes and seen how expensive they are and since I only need a small amount I figured I would just wait this battle out until harvesting time when I can start a new bin…hopefully before the end of summer. I have not looked into muslin but I have looked into the ‘Worm Inn’ design and their fabric choice, I may end up giving a DIY worm inn with muslin a try! :D Thanks!

Get your own gravatar by visiting gravatar.com Rhonda
#51. August 16th, 2013, at 5:29 PM.

Hello Carolyn,
I didn’t seem to see your message yesterday. Thank you for sharing your experience with me! That sounds like exactly what I am doing right now as well. It sucks waiting but they seem to be few in number each time I open the bin lid now, yay! I have stopped feeding my worms for now and am going to try and harvest some for a new bin soon. I think what happened in the first place is that I only had a small layer of bedding on top and my holes were not mesh covered. I put the bin outside and the flies must have gotten in that way to lay eggs. Now I have my bin holes mesh covered and a LOT more bedding on the top layer! I also have a container with the apple cider as previously mentioned in my bin for the fruit flies. Live and learn, now I know better than to leave my bin unprotected! Never again! haha

Get your own gravatar by visiting gravatar.com Rob
#52. December 29th, 2013, at 8:48 AM.

I see many posts here and other places about freezing scraps, but there is one here about microwaving. Is there a downside to the microwave method?

Get your own gravatar by visiting gravatar.com Diane Peel
#53. January 22nd, 2014, at 1:15 AM.

I am reading this as a prospective worm farmer, but keep wondering why there is so little mention of BT israelensis found in mosquito dunks (which I used for years) Gnatrol, and other drenches as mentioned by Carol #4I clear back in December 20I2. I usually grow lots of amaryllis around the holidays and allow my houseplants to enjoy the outdoors during our short summers; so fungus gnats are not strangers at my house. I am now using Gnatrol WDG and love it. It’s container tells me how much to put in my water each time I water to control the infestation of fungus gnats I am trying to control – moderate this time and due to some new houseplants I bought on sale.
I’ve used mosquito dunks for years, but never had a really firm Idea of how much I should use except what I could read online. The dunks are meant for mosquitoes so there’s no help there. In addition to the dunks I’ve tried many other ways of controlling f.g. sand and d.e. on surface,etc. Improving my watering habits became my first line of defense that and the Gnatrol (and the dunks before it) provided the most help. It will keep the tiny gnats/flies from being a dealbreaker in my quest for more and better compost. This is something my husband sees no need for – but he is very much against breathing and eating or otherwise ingesting gnats or flies.

Get your own gravatar by visiting gravatar.com Stephan
#54. January 23rd, 2014, at 11:50 AM.

Hello All, there have been some great comments here.

Below I describe the methods we successfully use to get rid of fruit flies.

Fruit flies are attracted to fruit and as such can often be found in worm farms, compost heaps and worm bins.

Although they are essentially not harmful to the worms they can become a nuisance if they are allowed to multiply.

They can be identified by plump bodies that are usually pale brown or orange and a slow flight. They are between 1 to 2 mm / 64th to 32nd of an inch big.

Mature flies lay their eggs on the peels of fruit, especially bananas. Those eggs are to small to be recognized by the human eye. When the conditions are right (warm and humid) the flies hatch and can quickly multiply if the environment is to their liking.

There are a few ways to reduce or even eliminate the fruit fly population in your worm bin.

———–

1.) Place all your fruit peels and rotting fruit that you want to add to the worm bin over night in a freezer before you put them into your worm bin. This will kill all eggs that are on the fruit and peels.

2.) Place the kitchen scraps for about 1 minute into a microwave oven to kill eggs that might be on the fruit and peels.

3.) When you want to add fruit peels and fruit to your worm bin dig a trench through the center of the worm bin and dump your waste into the trench. Then cover the worm food with already processed worm castings.

The casting will act as a natural barrier against the flies.

Another way to keep those tiny invaders out of your worm farm is to catch them with a trap.

To build a low cost fruit fly trap.

Take a large empty Soda plastic bottle, cut of the neck just above the place where the round turns into the straight line.

· With a sharp nail or scissors punch 5 or 6 holes 2 to 3 mm / 32nd to 48th of an inch in diameter into the side walls of the bottle about 10cm / 4 inches above the bottom of the bottle.

Throw a few banana skins into the empty bottle.

· Place the cut off top peace upside down into the opening at the top of the bottle base. It should look like a funnel now.

· Make sure that it fits tight and no gaps are left open.

· Attach the funnel top to the bottle base with some clear sticky tape.

· Place the trap a few meters away from the worm farm on an elevated place.

——-

It’s that easy! You can prepare a few of them slightly modified and place them in different locations to find out which works best.

Now open the lid of the worm farm and chase out as many of the fruit flies as you can than close the worm bin again.

The flies which have an excellent sense of smell will get attracted by the banana skins to the traps and crawl into the small holes on the side or the funnel opening at the top.

Most of them will not find the way out again. You should catch most of the fruit flies that have been inside your worm bin within 48 hours.

Once your traps are full either release them somewhere else or wait till they are dead and feed them to your worms.

If there are more flies left set up the traps again till you have caught the remaining ones.

———-

Fungus Gnats – are as well members of the fly family and are similar in size and looks to a mosquito.

They have a black slender body which distinguishes them easily from Fruit flies.

They get attracted by fungi and moisture and can be found in and around compost heaps and worm bins.

If you want to reduce the number of gnats in your worm bins

try to reduce the moisture levels on the surface areas of your bins (be careful and remember that the worms need a moist environment to live in.)

Or try to reduce the levels of food that you add to the worm farm.

We never really had a major problem with gnats and usually just ignore them.

Kind regards and happy worming

Get your own gravatar by visiting gravatar.com rou1
#55. January 26th, 2014, at 7:35 PM.

Fly paper work well in worm bins.It catches plenty of unwanted critters.

Get your own gravatar by visiting gravatar.com Stephan
#56. January 26th, 2014, at 11:34 PM.

Hello rou1,

that sounds interesting. Can you explain how this flypaper works?
Is it sticky?

Get your own gravatar by visiting gravatar.com Kenneth
#57. January 28th, 2014, at 9:12 PM.

Linda, what is SC vinegar

Get your own gravatar by visiting gravatar.com Anthony
#58. February 13th, 2014, at 6:32 PM.

I’ve heard the respiratory system small fruit flies have are weak. Does anyone know..
if I set a small contained fire in a worm bin, fire being in a container.. so smoke fills worm bin and kills small fruit flies. Will this also kill the worms.. or not?

Any experience with this?

Vinegar solutions, sticky traps, and other DIY systems don’t work for larger scale home worm bins.

Get your own gravatar by visiting gravatar.com Stephan
#59. February 14th, 2014, at 1:35 AM.

Hello Anthony,

compost worms are breathing through their skin and when the smoke penetrates their bedding it might very well kill them as well! Remember that compost worms are top feeders and will usually be close to the surface of your worm bin.

Consider fruit fly traps, to bury your kitchen scraps inside your worm bin and cover them with processed worm castings.

This works usually quite well. You can as well build some fruit fly traps as I described in one of my previous comments!

All the best and happy worming!

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