Fungus gnats

Discussion in 'Garden Pest Management and Identification' started by lily, Jul 23, 2003.

  1. Woodsprite

    Woodsprite Active Member

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    Fury2G,
    I really think it's great that it worked so well for you. I have this problem every year at this time and tried the lemon juice last year. Did okay for the live ones, however the newborns seemed to become immune. What a drag, huh? It's that time of year again and I need a new solution. Anyone know what's good for this problem in Maine?

    thanks

    Nancy
     
  2. cumulusnimbus

    cumulusnimbus Member

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    BTK is available in canada, however it is heavily advertised for caterpillars..but the specie of bacterium is the same no matter the advertisement.. it works very well if its used properly. the solution kills most sp of insect in its larval stage in soil. (which is important because that is the 'root' of the problem; is when they have an opportunity to reproduce.. ) most of these insects have a relatively short lifespan once adults so those can be taken care of with sticky tapes etc.

    the best way to prevent i think is to be aware of the plants on a daily basis, or to look at them once a week allotting a few minutes to each plant and observe. this way it is easier to eradicate problems at first indication.

    i have had plants in the past that have been afflicted with various things, i toss them! there are still many plant diseases that we are not fully knowledgeable of, so eliminate the risk of spreading early.

    hope this helps a little!
     
  3. chirita

    chirita Active Member

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    Thanks for your reply. I have also seen BTK packaged for use on mosquitos but was wondering what dilution to use for houseplants. Most of the instructions talk about putting one of the pellets in a pond. But how do I know how much of a pellet diluted in water would be OK for houseplants. Does anyone have any thoughts on this? Could too much BTK be harmful?
     
  4. cumulusnimbus

    cumulusnimbus Member

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    pellets!? i really dont know the science behind that at all! i have never heard of pellets as a product of btk. i was reading some journals on the effectiveness of btk. there are about 18-20 different varieties of Bacillus thuringiensis. the species of bacterium that is 'btk' (Bacillus thuringiensis kurstaki) is the one known (at least by me at the moment) to kill insects in their larval stage of life, not pupae not adult, only larval. and the bacterium itslef thrives in alkaline conditions, so in our acidic guts for example, it wuold not survive.

    i am not certain whether you can dilute a pellet and use it on houseplants. i wouldnt. but i am also very careful with biological 'cides'.

    if you purchase a bottle of BTK in liquid form i think its about 30ml for 10L of water. if my memory serves me correctly.

    can it be harmful? do we want to find out? probably not. UV breaks down btk, and cannot withstand acidic conditions... so i suppose its up to you!

    i am sort of in a rush! but i hope this post hasnt any errors and is helpful! i will post some more info if i get a chance to read today!!
     
  5. alabama

    alabama Active Member

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    I have recently tried neem oil in my greenhouse. It works for a lot of things. I haven't had bugs or mildew problems since. I love the stuff. It is safe for the environment and is non toxic to humans. The honey bees even came back. It is not supposed to harm them either.
     
  6. cumulusnimbus

    cumulusnimbus Member

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    YESSSSSSS!! i agree! great stuff!
     
  7. jimmyq

    jimmyq Well-Known Member 10 Years

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    The Bt for mosquitos is Bti (israeliensis) I believe. When I inquired (to the manufaturer) about how much to use when the product first came out I was told there isnt really a guideline. They said throw a handful in when you see a mosquito larvae population, do it again if they return.
     
  8. chemicalx

    chemicalx Active Member

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    I was just about to post a fungus gnat question when I found this very informative thread. Lots of good info here!

    My fungus gnat problem is with a Dracaena marginata that I got from my brother, and I'd been leaving it outdoors because of the gnats. I tried letting the soil dry out for periods of time, but it didn't seem to help. With winter fast approaching, I wanted to get it indoors. So I bought a package of beneficial nematodes and used some in the dracaena. (Also applied it in my yard, for the %$&! cutworms that clear cut my snap bean plants this summer.)

    But I'm curious what results others have seen with nematodes? Do you know how quickly I should see improvement? And is there much risk in taking the plant indoors when it still has some gnats? I don't want to infect my very healthy indoor dracaena, but the gnats don't seem to fly too far either.

    Also, would it be at all helpful to remove all the existing soil and repot in fresh soil?

    I also like the carnivorous plant idea, the lemon juice, and the vacuuming. I'll see if I can give those a whirl as well.
     
  9. Teri

    Teri Member

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    I seem to have these little black fly-like bugs in my Jade...so the soil is almost always super dry to start with...I only niticed the little suckers in the last two weeks, and I repotted a while ago. do I do it all over again? Will the plant go into shock or anything? I read somewhere here that i had to wash all the soil off the roots...will this harm a jade? HELP!!!
     
  10. tiger18

    tiger18 Member

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    Hi, I seem to have the same problem, though I'm not 100% sure if I have fungus gnats. The effects are similar, though. Leaves wilting, lots of black insects flying, little white worm-like things in the soil, and much more fruit fly-like insects.

    My plants are at the balcony, and we're at the 2nd floor so there's nowhere else to put them. At first only 2 plants were infested... then they're everywhere now (even if I isolated the infected ones). Most plants lost their leaves and flowers, and one mini rose bush died. The rest, however still have their stems and are budding new leaves. However, I've tried a couple of insecticides on them, but the new leaves just wilted. It didn't reduce the number of gnats too. Only one plant remains in decent condition -- the pepper plant.

    I've tried drying up the soil, using soap & water solution, using smoke to drive away the flying insects, and digging the soil daily... but they're still there. I guess I've been doing the wrong things. One thing's certain though: no more insecticides for me.

    After reading the previous posts, I'm thinking of resorting to using beneficial nematodes Steinernema feltiae or neem oil. I find them quite costly though... but what would you recommend? (I'm also thinking of trying the lemon juice trick)



    Thanks :D
     
  11. Newt

    Newt Well-Known Member 10 Years

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  12. pacemaker58

    pacemaker58 Member

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    This year I tried a couple of different methods of control. Nematodes are a proven solution for me, so I ordered some before bringing plants in for the winter. Watered them into every plant and problem was resolved.

    Come February a new batch of soil brought in more gnats. It was pretty obvious as the sticky strips (which had been up to monitor all winter) only caught very small ones at first.

    Rather than spend another $50 on nematodes, I decided to try Bti. Bought a bunch of mosquito dunks for $15 and simply added them into my watering cans. First time, I let them sit for 24 hours to disolve and break up. After that, I just refilled the cans and let sit until next watering. Dunks lasted a couple of weeks and by then the gnats we gone. New soil continues to bring more gnats, so I make sure I water the new soil with the Bti prior to using.
     
  13. soccerdad

    soccerdad Active Member 10 Years

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    I can't avoid wet soil: the time gap between the surface of the soil drying out and the plant starting to wilt for lack of water is less than 12 hours. Sad experience has shown this to be true. Maybe my pots are too small.

    I won't use chemicals as a matter of principle.

    Last year I tried using some sort of bacteria (or whatever) that you can buy in some plant stores where it is stored in a fridge. Totally useless.

    Then I put up the larger yellow strips - maybe 6" x 8"? - and hung one every few feet. Ineffective.

    This year when I planted my very first seeds I festooned the area with those strips, hanging them no more than 14" apart center to center. They are covered with dead gnats but they are keeping the situation well under control.

    The other ideas that I see here are very interesting and I will try some of them next year. But not the cinnamon: I sprinkled cinnamon this year on some pots, thinking that it would help prevent fungus/algae/whatever, but it killed every seedling that it touched.
     
    Last edited: Apr 23, 2009
  14. pacemaker58

    pacemaker58 Member

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    If stored in fridge, then likely nematodes. They have a finite lifespan so may have been dead when you got them.

    BTI is sold dry, either as granules or round mosquito dunks. Safe, as cost effective. I will use again next year.
     
  15. mudfoot

    mudfoot Member

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    This did not rid completly my fungus gnats but kept the problem under control. Three years ago I was growing American Chestnuts from seeds to eventually plant on our SE Wisconsin land. Quite by accident I discovered that when the gnats landed on the Chestnut leaves they stuck there and died. So now the problem has become finding sources of Chestnut seeds to have on hand to plant (they need cold stratification) and have them growing amongst my other indoor plants. This is a beautiful way to control an ugly situation.
     
  16. bones288

    bones288 Member

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    I've recently started my first attempt to grow 'indoor mung beans' but was unable to explain why my 5 plants were all dying off one-by-one. Then I found that when I pulled a dead plant up by the stem it would pull straight out of the soil like a straw. It looked like the roots were stripped bare. So I found that those harmless 'fruit fly' things were destroying my plants from under the soil. :(

    One solution I'm in the middle of trying is to lay a half inch of plain old sand on top of the potting soil. It seems that the flies can't get close enough to the soil to lay more eggs and the last batch of flies disappeared. Bcs the sand doesn't touch the eggs in the soil I've found (as of today) that I now have 4 new baby flies floating around the plant looking for a way in. I have to wait until all of the eggs have hatched before I try to remove the soil.

    I found the vinegar (in place of lemon juice) did very little to clear the problem (I only caught two) but because of this sand trick it looks like my last plant might actually make it!
     
  17. bones288

    bones288 Member

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    Side note: the first thing I tried was to get a venus fly trap to catch the little buggers but, because I bought the plant at a fair, it was so inundated with spider mites (I think) and some type of worms that I couldn't bring the fly trap into the house. Prolly wouldn't have worked anyway.
     
  18. gardentastic22

    gardentastic22 Member

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    We had a big problem with these, especially when trying to grow chives, and were informed to buy a product called vectrobac (a product used to control mosquito larvae) which worked very well in removing them, however was a little expensive and took a few weeks to get rid of them completely. The other way I was informed of was to put out a jar of strong vinegar to catch the gnats themselves in, was not the best method, but still killed a few of them in the process.
     
  19. ContainerGirl

    ContainerGirl Member

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    I only have a couple of containers right now that are infected with fungus gnats. Will the mosquito dunks hurt any uninfected plants if you use the same watering can for both?
     
  20. Pierre16

    Pierre16 Member

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    Re: Fungus gnats: USED COFFEE GROUNDS

    Half an inch of used coffee grounds will form a dry crust on top of the soil and do like sand, prevent flies from laying eggs. However, as with sand, you will not know when your soil is dry and needs watering... but it is deadly to knats!
     
  21. victorw8856

    victorw8856 Member

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    Re: Fungus gnats - the bane of my existence

    This post has been going for 7 years now! Obviously I am not the only one having trouble with these demonic pests.

    I have been plagued by these things for two years. 5 house plants have died, the rest are choking along.

    Here is what I have tried and experienced:
    - let the soil dry and don't overwater...doesn't do anything for existing infestations

    - use Bt....tried it several times, using two varieties including Bti. Fungus gnats laughed at it.

    - nematodes.....the fungus gnats ate them for breakfast and asked for more.

    - apple cider vinegar to attract them.....didn't work, they were too busy flying into my lemon water.

    - potatoes....applied and changed out religiously every day for a month. Fungus gnat larvae said "thanks for the food, man!"

    - Sevin (Carbaryl).....tried dust and liquid forms. Plants gagged a bit, fungus gnats said that I got no game.

    - "Knock Out Gnats" by GardensAlive.....applied several times per instructions. This stuff couldn't knock out a half-drunk starving fungus gnat. Returned it for my money back, credit GardensAlive for giving me the refund.

    - Hydrogen Peroxide to kill the larvae.....oooh, now this was exciting, the soil starts bubbling all wicked-like. Surely this will kill 'em! Fungus gnats and larvae drank it up like champagne.

    - yellow sticky traps in conjunction with various combinations of above treatments.....killed A LOT of adults, but the next generation just kept coming like a class B zombie horror movie.

    Ideas I am dismissing:
    - Mari...<something> 50 -- can't even get it anymore, probably a good thing
    - cinnamon.....heard that it kills some plants, bad idea
    - making a treaty with the fungus gnats.....they can't read.
    - A bomb (no, not an insect bomb, a real bomb).....neighbors would get pissed.

    Other ideas I am going to try:
    - top layer of sand or shredded coconut husks.....hopefully it won't just be another day at the beach for the gnats

    - sundew carnivorous plant.....even if it doesn't work, this idea is just too cool not to try.

    - repotting all of my 20-25 houseplants. $$$ and time, baby!

    Anyone else have any other ideas?
     
  22. Michael F

    Michael F Esteemed Contributor Forums Moderator 10 Years

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    Every time I find a small spider or a centipede in the house, I put it into the plant pots. Takes time to work, but it does work eventually. The only successful remedy I've ever found.

    Down side is all the spider's webs decorated with sucked-out fungus gnats, strung between the leaves of the plants ;-)
     
  23. estelle james

    estelle james Member

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    Hi, I am a new member and think I have something to contribute! I top dress my fungus gnat prone plants with sand or granite grit. In addition to drying out the soil surface, the buggers (literally) don't like the sharp edges of the material. They usually disappear quickly with this treatment.
     
  24. Gabriolan

    Gabriolan Active Member Forums Moderator

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    Re: Fungus gnats - got rid of them!

    Last week about a million fungus gnats appeared in my garden, and I was pretty upset about that. I came here and read through this whole thread for answers.

    I tried a bunch of stuff. I put out a saucer of apple cider vinegar, and seven of them drowned there. None of them were interested in lemon water or beer, though wasps drowned in the beer I put out.

    I filled my sprayer with the organic fertilizer stuff I use for foliar feeding. The stuff is made from seaweed, all concentrated down. I put the standard amount of seaweed fertilizer into the sprayer, added water, and went about spraying all plants in the garden.

    Fungus gnats were all over the plants, so many of them got sprayed as well. Next day, those gnats were dead, frozen in place. There were maybe three live gnats. I sprayed again, skipped a day, and sprayed again. No more gnats!

    I suppose it's possible that the gnats are underground eating roots and they'll still be a problem -- I don't know enough about them to know. But for now, at least, they're gone.
     
  25. awallace

    awallace Member

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    I just wanted to report that I have had success controlling a fungus gnat population using bti laced water. I eliminated the gnat issue for a few months by incorporating Nematodes. I cant wait to try out the sundews!
     

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