Fruit Flies

shera_2006June 29, 2006

Help Please,

I have these breeding in the houseplants at work could anyone tell me how to get rid of them otherwise I will have to throw away around 40 plants they are completely healthy otherwise and it will break my heart. It seems that they are living and breeding in the soil.

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audreye(5b Ont)

Hi Shera

Are you sure they are not fungas gnats? They are very similar looking to fruit flies, maybe just a tad larger and darker in color. Fungas gnats love wet and damp soil? Do you let your soil dry between waterings?


    Bookmark   June 29, 2006 at 3:12PM
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I second the fungus gnats. They love living in arid air and wet soil.
I agree w/Audrey about allowing soil to dry between waterings..If you have a small, rotating fan use it for air circulation. FG's usually appear in winter homes when air gets dry. Cut back on watering and you should see improvement. Toni

    Bookmark   June 29, 2006 at 7:49PM
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rhizo_1 (North AL) zone 7

Gnatrol or mosquito dunks dissolved in water will do the trick very quickly. It goes into the water and you apply it every time you water for a few weeks. They will kill the larvae. As the adults only live for a few days, you will soon be fungus gnat free.

Some potting mixes are simply fungus gnat generators, no matter how careful you are about watering. If the problem is a serious one, best to get rid of the darned things ASAP, and then learn how to prevent them from occurring again by changing your potting medium, watching your watering practices, by applying a layer of coarse builder's sand on top of your soil, etc.

    Bookmark   June 30, 2006 at 9:19AM
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i have to say that i have the same problem. it seems to be in all of the plants i recently re-potted with a new soil.. do they hurt the plants at all? i don't really see any damage to the plants at this point..curious to see if you found a solution?

    Bookmark   July 24, 2007 at 12:34PM
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I have some herbs under lights in a 15 gal open aquarium and its alive with gnats. Currently I am making do with sticky traps but I just ordered Gnatrol, and hope it gets here soon. It would be a shame for you to throw out all the plants, Shera, hope its not necessary, especially since they are otherwise healthy. But those darn gnats are so annoying...good luck!


    Bookmark   July 24, 2007 at 6:27PM
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Ash, what type of soil did you buy? It wasn't Hyponex, was it? I buy Hyponex but mix in Perlite and sand..Otherwise it's too heavy to use alone.
The soil is black..many times you'll find huge clots of soil balls..Does this sound like the soil you're using? And if so, do you add a second or third medium? Toni

    Bookmark   July 24, 2007 at 7:53PM
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The easiest way to get rid of fungus gnats is to buy a solution for them......I just got some from a hydroponics store, I will be trying it this weekend.


    Bookmark   July 26, 2007 at 5:00PM
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Don't trash your plants. Fungus Gnats can be beat! I have not used Gnatrol, but I would bet it has bt as the active ingredient. I use Gnat-away from GardensAlive (bt is active ingred). Bt will kill the larva stage. Then for the adults... set out yellow bowls of soapy water or bowls of soapy water dyed yellow, or use the yellow sticky traps. You can also make sticky traps by spreading a little STP engine treatment on anything yellow (cut pieces from yellow solo cups for example). I also use ferti-lome systemic (available at Ace Hrdwr) sprinkled on the soil and mixed in when I repot. You can also use a flying insect spray around the plants but not directly on leaves. Hold the can out a several feet (this one is riskier to the plants). If you take these steps it will cure the problem. I always get fungus gnats this time of year. I think they come in on produce. I usually get them in late winter too.

As already stated, I think letting your soil dry out completely between waterings and loosening it with perlite is a good idea to prevent gnat infestations and also for the health of the plant. I've been growing houseplants a long long time and I don't know if you can completely avoid having outbreaks of these nasty critters. They are very common.

I can't swear to this, but I have heard from several plant friends that Miracle Grow potting mix is a big risk for bringing in fungus gnat eggs. One friend contacted the company and they simply said they did not present their product as being sterile. Such concern for your customers is touching don't you think?

Don't give up on your plants! There are always challenges.

    Bookmark   July 26, 2007 at 7:24PM
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buyorsell888(Zone 8 Portland OR)

Miracle Gro makes a moisture retentive soil that is very easy to overwater.

Doubt the eggs are really in it.

Hyponex is really heavy too.

Mosquito Dunks are BT and can be used same as Gnatrol.

No reason to throw away plants infested with fungus gnats.

    Bookmark   July 27, 2007 at 4:23PM
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I would avoid the moisture retentive Miracle Grow at all costs if you don't want bugs! I potted 5 pots with it and all of them have both gnats and even quite a few centipedes! They are all from the soil mix because neither plant nor soil has ever been outside!

    Bookmark   October 26, 2007 at 2:27PM
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these posts have been really helpful - these flies/gnats waged a fierce war against our lavender and basil plants which had been previously quite healthy, and sad to say, after a couple months of fighting the flies/gnats seized the day and took our poor plants - most recently they have gone after our money tree and our cane tree - these darn gnats are everywhere - as of today they have completely eaten up the leaves on the money tree and have settled into the soil of the cane tree pot.
thanks to these posts we realize it was the miracle grow soil that brought us these tiny tyrants - we will try your suggestions and hope we rid ourselves of these little buggers.
thanks! and HAPPY HOLIDAYS!! (we secretly fear they will wage their personal war on our Christmas tree - we shall keep you posted)

Question - why are they so attracted to yellow?

    Bookmark   December 16, 2007 at 11:54PM
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watergal(z6/7 Westminster, MD)

I think you may have something else going on as well - fungus gnats don't eat leaves, to my knowledge.

I learned that whiteflies are attracted to yellow because it is the color of leaves on a drought-stressed plant. Don't know if that applies to fungus gnats as well - probably not, since they like WET plants!

I don't like MiracleGro soil for the same reasons, but gnats can come in on good quality soil too. I always try to buy my potting media from a place where it has been stored dry, not outside in the rain, but that's not always possible.

    Bookmark   December 17, 2007 at 7:31AM
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I have a similar situation as described above but the flies that are in my home are nowhere near my plants or near my garbage/composter (where fruit flies would be) ..These flies which resemble fruit flies are everywhere else in the morning though i do find close to half a dozen inside my lamp shade and on the inside of my window sills..what are these annoying little guys called and how do i get rid of them?

    Bookmark   February 3, 2009 at 6:14PM
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mschwartz(zone 7 georgia)

I have the mosquito dunkin donuts for my rain barrel. How big of a piece would you put in a gallon of water?

    Bookmark   February 6, 2009 at 7:14AM
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watergal(z6/7 Westminster, MD)

It is possible that they could be shore flies, which like to live on the gunk that can accumulate in drains. Google "shore flies", I think you can pour bleach or ammonia or something down the pipes to help, but I don't recall the details.

They could still be fungus gnats that have escaped from your plants, though. Are your lamp shades or windowsills yellow, by any chance?

    Bookmark   February 6, 2009 at 9:42PM
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The lamp shade is white as is the light from the bulb and the window sills are an off white.

    Bookmark   February 8, 2009 at 3:54PM
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These postings are very helpful in saving my beloved plants.
Some questions
1. If I choose to repot a plant with a few gnats (not infested-yet) should I try to get all the soil off the roots? Won't that damage the roots?
2. Since the gnats are worse in the dry winter air, while letting the soil dry out, is it a good idea to spray the leaves with lots of water?
3. Do these gnats cause leaves to fall - is that one of the symptoms?
thanks very much

    Bookmark   February 11, 2009 at 9:17AM
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1) It depends on the plant. Some plants' root systems can take a beating, others will die almost instantly if removed from soil.

2) Yes, you can spray the leaves at night, as that is when the pores open for respiration.

3) I don't think so, but many plants drop leaves in the winter for no reason other than that's their natural cycle.

    Bookmark   April 6, 2010 at 10:38PM
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rhizo_1 (North AL) zone 7

There's no need to get rid of all of the soil, march. Gently shake off all that you can and repot.

Who said that fungus gnats are worse in the dry winter air? Moisture is what kicks them into high gear....moist potting soil.

Misting at night will accomplish nothing, I am afraid. It doesn't water your plant, it doesn't raise humidity around your plants for more than it takes for the foliage to dry, and it may encourage foliage diseases.

Respiration occurs all the time in living organisms. It's easy to think of photosynthesis occuring in the daylight, so respiration must happen in the dark, but it's not the case. In most plants, the stomata close at night. In most plants they are open during the day to expel O2 and water vapor and to access CO2 from the air. Much of the CO2 generated by respiration is stored within the plant and used for the photosynthesis process, also.

Stomates will also close (besides at night) during periods of high temperatures when the plant cannot take up enough water fast enough to maintain turgidity within the cells. Turgid stomatal guard cells are open. Stomata may also close when the plant gets rained on or misted. One more reason NOT to mist your plants on a regular basis.

    Bookmark   April 7, 2010 at 5:10AM
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We currently got a plant from a neighbor with much of these flys/gnats in the soil. Someone told me to spray the soil with a combination of soapy water and rubbing alcohol. I have been doing this for 3 day and the flies seem to be disappearing! I'm not sure if there will be any affects on the plants, however, last year we had herbs and tried the same thing. When we sprayed the herbs, we left it on the plant and did not rinse the leaves well enough and the alcohol burnt the leaves. Again, Im not sure of the effects on larger plants or spraying on soil only, but I would rather try this method on the soil for a while and see if the plant lives rather than having all those flies living with the plant. Good Luck!

    Bookmark   May 8, 2011 at 4:49PM
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My bearded dragon died at the end of Feb. and I turned his 75 gal tank into an indoor herb garden....I have THOUSANDS of gnats!!! I also used Miracle gro :( I don't know how to get a handle on this, I also bought 6 palm trees, different kinds, and I have these gnats in the tank and now all over my apartment!! I got one of those yellow sticky things and hung it in the tank, it was BLACK in 3 days!! Completely black at least a thousand on it, can't see any yellow at all but it didn't make a dent in the gnats!!!!!
I will try everything you guys have suggested till it's gone. I am on a fixed income, disability, and I spent way to much $$ on these plants and the three 30lbs. bags of miracle gro :( I'm glad I found this site, I hope it works.

    Bookmark   June 27, 2011 at 2:46AM
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I mist my plants with a combo of alcohol and water. Then someone suggested putting scotch tape on the rims of the pots (the yellow kind) for the buggies to stick on and die.


    Bookmark   June 27, 2011 at 7:34AM
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Ang..One Yellow Sticky Trap isn't enough. Do you know the trap brand?
If it's a store-bought trap, they can be washed and reused, but if your house is loaded w/gnats, (sounds like it is) you really should purchase several traps.
They're sold in online garden centers/nurseries, and Ebay, reasonably priced.
These traps saved my plants one year.

Are your plants indoors? When you speak of Bearded Dragon, do you mean the outdoor garden plant? Think it's Iris??

There are three things you need to do.
1. get more traps.
2. allow soil to dry between waterings.
3. fresh, flowing air. Open a window/s and/or run a fan, 'do not aim at plants,' for air circulation.

Check, 'Garden's Supply' for pricing.
You can make your own traps, but the glue, 'Tanglefoot' is expensive. Plus, you'd need to make/find yellow cardboard. Yellow attracts insects.

Hopefully, Susan's idea will work,,, Toni

    Bookmark   June 27, 2011 at 3:28PM
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Spread diatamaceous earth on the top of the soil. It cuts them as they move through the soil and they die. Worked for getting rid of them in our office when they had gotten out of hand.

    Bookmark   October 14, 2011 at 9:39PM
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I had a horrible time with fungus gnats last year, even with yellow cards and pesticides. What I ended up doing was replacing all peat-moss-based mix with coir-based mix. Peat moss ban! And now I am bug free, and the plants are happy. I highly recommend switching.

    Bookmark   October 19, 2011 at 10:19AM
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jessiec777(Washington State 5)

I had a fight with fungus gnats this summer. I had no clue what they were at first. I bought some hyponex soil for my outside potted herbs. I figured outside in 90+ weather everyday there wouldn't be a problem. I'm sure if wouldn't have been if the soil hadn't been infested by them. I didn't think much of it at the store, but I saw them crawling around the potting soil bags.
I got rid of them by tossing the outside herbs and then putting a layer of sand on top of my house plants. I also put some cinnamon on top. I know it sounds weird, but they were out of here fairly quickly.

    Bookmark   October 19, 2011 at 10:43AM
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rhizo_1 (North AL) zone 7

LOLOL...I think Ang's bearded dragon was a big lizard, Toni. ;-)

    Bookmark   October 19, 2011 at 12:53PM
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