Saturday, November 14, 2009

Tiny Black Bugs - Fruit Flies or Fungus Gnats?


In lieu of a dog or cat, we have various insects living at our house. Most prominent lately have been these tiny black flying things. But they're too small and too active to really get a decent picture. But this week I found one floating in a little water at the bottom of a cup on the table. These guys sometimes seem to come home with bananas and they like any kitchen scraps we haven't covered well before taking them out to the compost. And we're at the season change time when our backyard compost takes its winter break and we haven't quite gotten used to the garbage disposal yet.

But with a picture in hand, I finally called Cooperative Extension to see if I could identify the little critters. Because they liked the fruit he thought they might be fruit flies, but when he saw the picture he called to say they were Fungus Gnats.

He sent me a link to the Colorado State  Extension site where I learned:

Fungus gnats (Bradysia species) – also known as dark-winged fungus gnats, are small, mosquito-like insects often found in homes and offices, usually in the vicinity of houseplants. They are considered a nuisance when present in noticeable numbers, but the adults are harmless insects that do not bite. Fungus gnat larvae develop in the growing medium of houseplants and are considered minor pests of houseplants. . .

They are really small, I took another picture with a grain of uncooked rice floating next to it.
The most important strategy to minimize fungus gnat problems associated with houseplants is to allow the growing medium to dry between watering, especially the top 1 to 2 inches. The dry-growing medium will decrease survival of any eggs laid and/or larvae that hatch from the eggs as well as reduce the attractiveness of the growing medium to egg-laying adult females. In addition, it is recommended to re-pot every so often, particularly when the growing medium has “broken down” and is retaining too much moisture. Furthermore, be sure to remove any containers with an abundance of decaying plant matter such as decayed bulbs and roots, which provide an excellent food source for fungus gnat larvae. . .

 Want to see if there are larvae growing in your potted plant soil?  But do you really want to find these guys?  (The larvae picture - on a potato - is from the Colorado State site.)


"An effective means of detecting the presence of fungus gnat larvae is to insert 1/4 inch slices or wedges of potato into the growing medium. Larvae will migrate to the potato and start feeding within a few days. The potato slices should be turned over to look for larvae present on the underside."
And the fruit fly?  That looks totally different.  Picture and text are from an Oklahoma State webpage


Life Cycle: Female fruit flies lay their eggs on the surface of rotting fruits and vegetables. Each female may lay as many as 500 eggs. These eggs hatch into larvae which molt twice before becoming fully grown. The larvae feed on the yeast organisms and fungi growing in infested material, and through their feeding efforts, they soon turn their food into a semi-liquid "mess." When the full-grown larvae are ready to pupate, they leave the food material for dryer areas. Complete development from egg to adult under summer conditions may be completed in 8 to 10 days. Mating takes place soon after adult emergence, usually within a few hours, and egg laying begins about 24 hours later.
There's a lot more on the links if you want to know more. 

45 comments:

  1. Could you save me one of those bugs Steve? We just bought a great microscope and I'd love check them out up close.

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  2. I had these little buggers once and found they came from the potting soil I bought at Fred Meyers. I had bought several bags and repotted all of my 79 house plants OMG what a disaster. I had to buy all new soil, wash the roots of all my plants and sterilize all the pots. Now I check the soil before buying it and never buy it from FM's.

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    1. NEVER buy organic potting soil for inside plants - I learned THAT the hard way! Too bad the bags don't say that, since we all think we're doing the best thing.... Kate

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    2. Thanks, guys. Due to the change of weather, all of my deck plants were brought inside (I used garden soil to plant the ferns). Now I have hundred of these little buggers. I have several 4ft ferns and I am nervous about letting them completely dry out so I am going to try Diatomaceous Earth sprinkled on top of the soil. I'll do and update in a few days...

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  3. does anyone know how to get rid of them using household prducts?

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    1. I have fungus gnats every summer during compost warm weather, but they usually leave when it gets colder.. Apparently they love fungus for their babies, and I heard cinnamon will stop any fungus growing, so I sprinkle cinnamon on the plant soil, and they just left in a hurry.. Do not leave any moist foods around, as they may also plant the fungus there for the babies... so if I have some moist foods , I just sprinkle the cinnamon on the apple slices etc... or even a stir fry for later... hope it helps a bit. They seem hard to get rid of, as there is always an onion or potato going bad for them to take the fungus to a better place, I imagine this.. not sure they do... mary.

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    2. Gnatrol, purchased at Amazon, totally freed my houseplants. Water at regular intervals.

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    3. I have been seeing an abundance of the little black gnats(flies) flying in from my balcony they are creepy and although they don't bite they do land on me and itch my skin. I prayed OFF on the balcony door and instead of repelling them they are attracted to it or something but when they land on it they die. Every morning I'm washing off about 200 off of my door.
      Any advice? I would like to use my balcony again.

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    4. J.C. - if they are the same critter, they seem to be much more abundant seasonally and then disappear. Not sure where you are, but if it gets colder, they'll probably die off. (You had the same comment up twice so I got rid of one. But now that I've read more carefully, maybe the other one had sprayed instead of prayed. Sorry if I cut the corrected one.)

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  4. I have one of thse little critters. No matter what I do I can't get him. Please tell me how, he is driving me crazy. I think I have caught him, but then I open my hand or the place where I hit him and he is not there. There has got to be a way to kill these annoying, pesky little things.

    navygirl

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  5. Couple of suggestions:
    1. put a very ripe banana into a deep pot and hope the bug goes to the banana. Then put on the lid and take it outside.

    2. use a vacuum cleaner to suck it up

    3. go on a vacation and it will be gone when you get back

    Good luck.

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  6. I work for Orkin... best way to get rid of fungus gnats is to stop watering the plant for a while. They're there because of the excess moisture that can exist in potted soil. They thrive off of it. Stop watering, let the dirt really dry out, and you'll find they don't come around anymore.

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  7. fruit flys love red wine. Leave a cup or open bottle of red wine and you'll be amazed how many you will catch (they will drown) in the red wine.

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    1. Less expensive to leave a cup of vinegar for them to drown in.

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    2. That assumes one has "extra" red wine...lol

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  8. All you have to do is take a small container about the size of a pudding cup and put about a half inch of cider (orange) vinegar in the bottom, add a pinch of sugar to make it sweet and it will attract the flies/gnats then add 3 or 4 drops of dishwashing liquid to the vinegar mixture. The dish soap cuts the surface of the liquid and they cannot fly out - they drown. If you have fleas that you take off your dog or cat, you can put a small cup with water and 2-3 drops of dishsoap in that and then put the fleas in it as you pick them off your pet. They sink like stones and drown. Clean, Green and takes care of your problem without pesticides.

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    1. I accidently left 1/2 inch beer in a can for a few days, and when I dumped it in the sink to rinse out, , many fungus gnats dropped out. about 30 or more.. so now I leave some around the door where i think they come in from the compost bin in back yard. If you want to protect food from their fungus spreading habits, sprinkle a bit of cinnamon over it.. they all run away because they live off fungus, and spread it around to lay their babies in. The wine is a great idea and does catch a lot... a narrow top would be better I think , as well. good ideas thank you. I heard that sprinkle of basil on food keeps fungus away. maybe many herbs do.. I wonder if cinnamon would work on fruit flies too?? What about flies around worm composting bin?? just wondering if anyone has worked with these?? ., and would cinnamon harm the worms ?

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    2. Thanks for the beer and cinnamon tips. I'll definitely try the cinnamon.

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  9. Anon Sept 5, Someone just told me a very similar methods, except he added a cover to the jar - I don't recall if it was saran wrap or just plastic bag - and poked little holes in. They could get in, but if they could still fly, they couldn't get out. I did a simpler method at my mom's when there were scads of them. Just put some fruit in a plastic back with the opening up in the air and made small. Then when there were a lot in the bag, I just squeezed it shut and took it outside. Thanks for commenting.

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  10. How long will I have these things!! I bought Knat/Fly ruit fly traps today. They are covered with these things. How do you keep them gone? Do they bite? HELP they are gross!

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  11. Anon, sorry about your infestation. I don't think I can add more advice than is already there among the comments. Good luck.

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  12. Help! What I have is something quite different. They are black, about an 1/8" long with translucent wings that may have spots on the tips. They do seem to be some type of fly. They swarm and they seem to appear only this time of year (November). They are outside, not inside, but my doors and windows become covered with them. When a door or window is open, they do come inside but do not seem to fly around too much inside. They mostly congregate near openings. They will fly up around your head, somewhat like gnats, when you through a swarm. I had this problem at a former house I owned, and I've seen them in windows of commercial buildings.

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  13. Anon 11/5/12, Sorry to hear about your infestation. I'm not really an expert on this. And you don't say where you live. If in the US, I'd suggest you contact your local Agricultural Extension Service. Here's a webpage where you can locate your local office:
    http://www.csrees.usda.gov/Extension/

    Since you have so many of them, I'm guessing you could catch a few to show them. But if there are so many, I bet they will know. Let us know what you find out.

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  14. i have what looks like fungus flies. They come into two windows in our home around the same time each year. They don't bite and their life span is very short, but there are hundreds of them and they are annoying.

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  15. I have them. This is the first year. They are not fruit flys. The do like water though. The dogs bowl, the dish drainer. I find them dead every morning. They fly around us too. Won't go after the vinegar water trick.

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  16. mine don't go after the vinegar water either. I've had them for years, but this year they are worse than ever. I thought they were drain flies but they are never near the drains - i never see them around fruit, and I'm a fanatic about food and garbage lying around. I also have many houseplants and one in particular that I brought in from the garden in the fall. It was just too beautiful to see it die off. I finally decided I had to do something about these little devils - it's embarrassing to have them flying around guests. I finally got a close up picture of a dead one and compared it to the photos of a variety of little flies shown on the web - eureka! it's a dead ringer for a fungus gnat. I just ordered something on amazon that's guaranteed to eliminate them - we'll see. I'll report back if they work

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    1. Good luck jpallen. Waiting for your follow up report on what you used. I'm leery of chemicals. I've found a piece of banana or sweet juice in the bottom of a big bottle would collect a bunch of them, then I can put the cap on the bottle quickly and take them out. Buddhists can then release them, others can do what they want.

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  17. Try Beneficial Nematodes to be fungus gnat free. There's a great YouTube video explaining the use in greenhouses. It is environmentally friendly... No chemicals at all!

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  18. In the soil of houseplants look for Fungus Gnat larvae. They're maggot like appearance, translucent, thinner than 1 mm, about 3 mm long. The larvae live in the surface soil that is constantly humid and rich in compost. Remedy could be changing watering pattern to create longer periods when the surface soil dries out. If it didn't help try changing soil to one with less compost and refrain from overwatering.

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  19. I find their dead bodies each morning, collected on my stove hood light shade. Never see them flying around. I never have any fruit. I do not have any plants. I don't see them in the dry cat food bag as I checked. I don't catch them drinking the cat's water. At least they gravitate to the light and die. But don't know why they come in, what they feed on or why they stay.

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    1. Yours might be sewer flies. They come when there is a break in a sewer line inside or outside. They enter through drains.

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  20. Thanks for all the advice. Had zillions of these at the sliders and big kitchen window. They may be due top the severe Boston winter since they suddenly appeared once the snow melted, even though the plants have been indoors all winter. The eggs must be REALLY small, cause the MOST creepy part was having a few INSIDE the dual pane windows (which obviously must be leaking now).

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  21. Predatory nematodes are excellent for fungus gnats. They come in a small sponge that you add to the water that you water your house plants with. They are microscopic so you can't see them. They eat the larvae in the soil. No pesticides! Usually hydroponic supply stores have them.

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  22. I find them around the laundry, kitchen, basement and also in my master bathroom sink but I have no plants or food in my bedroom on a second floor. Would it be possible that they travel there or I am seeing a different annoying tiny black bugs? I don't see them all the time of the year but do have them right now. will try some of these suggestions. Thank you!

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  23. All of these tips are very interesting and informative. I am now pretty sure I have fungus gnats in the house. Not too many I may see 1 or 2 a day. Sometimes I find a couple dead bodys on the stove light and I believe they gravitate to light from the computer. I do have house plants and will try letting them dry out, but I really am not very dedicated to watering them. I am going to try the potato to see if there is larva. Thanks for all the help.

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  25. Thanks again Steve! Your blogposts come in handy all the time. Keep up the awesome work! You Rock!

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  26. Lysol Spray, spray on top of soil, in household garbage containers, under sinks in kitchen and bathrooms. The Lysol dries on top of soil let plant soil
    Dry about 2 inches and when you water dry Lysol reactivates and goes down to kill larvae

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  27. Hoping someone sees this who can help... I saw fungus gnats and dealt with them. I consider them shaped like an airplane yet not as dense as drain flies. Now I'm seeing a smaller flying thing, shaped like a teardrop and they like light. I've got a few that landed on my eReader screen and are only as big as one letter. Any ideas what they might be?

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  28. About 8 neighbors ranging within a block are experiencing these fungus gnats and fruit flies inside only. Pest company has been unable to control them after several visits. The house has been bombed and bleach and citrus has been placed in the sinks then they return. There are no plants in the houses and all fruit has been placed in refrigerator. The utility company visited to snake each of the homes pipes with cameras and found nothing. A plumber does not feel the gnats are a drain problem. Any suggestions as to why several homes are being affected? Thanks! Sarah

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    1. I live in Ohio — also have NO house plants (I have a black thumb) and have been infested with these little beasts since the drains backed up in my basement during a torrential rain. NOTHING is affecting them, and they’re not the drink flies as they match what’s in the photo. Anyone with any suggestions?????

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    2. I've seen people using very sticky strips of paper that you can buy at gardening shops. Some twist around so there are lots of surface for them to land. Good luck. Let us know what happens.

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  29. Sarah, let's see if any readers can answer your question. Perhaps they are coming in from dirt that's in the garden. I just don't know and you've called in your local experts. Good luck! You didn't say where you're from, but looking at my tracking software (Stat-Counter) I'm guessing you're in Florida, if that matters to any bug sleuths who might help you.

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