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How To Kill Fungus Gnats With Hydrogen Peroxide

Discussion in 'Sick Plants and Problems' started by Reverend Bud, Feb 5, 2010.

  1. know that this will kill any beneficial microbes in organic soil
    but yes, it's an option

  2. Exactly why i was so hesitant in the first place to try this.  I couldnt believe such extensive article on h2o2 hadnt even mentioned killing the bennies.  But after the treatment i used compost tea and molasses to rejuvenate a healthy microorganism population.  The pyrethrum works pretty well and the lady at the gardening shop says the larva are usually content chewing on organic material in soil and only in infestations will they go for roots.  Plus im sure they love the molasses so as long as things go as they are now im content to coexist. 
    But the satisfaction i would have had taking the hose to those buggers would have been too much! Did you actually see larva? I'm having trouble distinguishing larva from other little guys.  Anyone know if the larva jump around at all? 
  3. Has anyone tried cinnamon?
    I just salvaged four plants someone was throwing out, and re-potted them yesterday.  I know there's a massive fungus-gnat onslaught coming soon as a result.  These plants are indoors.
    I want to take any kind of action I can to head this off early.
  4. Have not heard anyone mention cinnamon yet but readily available remedies are my favorite! The yellow sticky tracks really took a bite out of the gnat numbers. I went from seeing several hundred over a week to maybe 2 dozen a week using traps and so spraying pyrethrum once a week on the foliage
  5. I've seen several references to cinnamon as a remedy (like this), and the reports on it seem to be about as positive as anything else.  It's surprising how there's so little solid information on what does or doesn't work on this scourge.
    I haven't found any insecticides to work in the past, except one: the Raid foggers that come in small orange cans.  Those wiped out the exposed flies, but of course didn't kill the batch gestating in the dirt.  I've sprayed regular Raid (don't remember which formula) directly into the dirt and it didn't even kill the adults.
    I also read that the flies won't tolerate swiftly moving air, so I put all of my plants in front of a fan that was aimed down at them on high speed for about a week straight.  Worthless; still had flies galore.  Then again, this wasn't a conclusive study if the gestation period is up to two weeks.
  6. i would avoid anything like raid, if it seeped into your soil in the next watering that would do much more damage to your roots than the larva.  working with cabinets ive noticed that a lot look to be dying of thirst, after i water there are maybe 75 gnats in the drainage bowl drowning in the run off.  i think when the adults can no longer feed on the sap from foliage (due to pyrethrum spray once a week) they dehydrate so long as water is not around and the set up is kept tidy.  the sticky traps are your best friend, i have 2 in each cabinet clamped with the lights and they caught near 800 in 6 weeks.  no visible damage to plants at these concentrations of gnats either. the main thing that pisses me off about them is with no fail they always find their way into my morning cup of coffee. every damn time.  
  7. sticky traps and azamax
  8.  My hats off to you Tin Tizzy...an elegant reduction of the problem to a simple solution.....and a rhyme for a reason....thank you 
  9. #49 Stokestack, Jul 19, 2013
    Last edited by a moderator: Jul 19, 2013
    Since I was freshly potting these plants I decided to do the cinnamon test.  I bought two big-ass containers of cinnamon from Costco, stripped the top couple of inches of dirt out of three of the four pots (the last pot wasn't even full yet), and mixed the dirt and a significant amount of cinnamon in a bucket.  I then re-applied the dirt, carefully creating an even layer that totally covers the underlying soil.  In the last plant, the entire top half of the soil is cinnamon-infused, including a lot that's in direct contact with many of the roots.
    I had already watered each of the plants, and didn't do so again.
    I had some cinnamon dirt left over, so I applied it to the two other small plants I have in the house.
    It has only been a week, and so far so good.  I wasn't willing to make this truly scientific and have a control plant with no cinnamon, because I don't want to give these flies a foothold at all if I can help it.
    I also found that after being reapplied, the looser cinnamon-infused dirt dried out pretty quickly.  This will also deter the gnats, and further muddy the results of the experiment.  I'll keep you peeps apprised as time goes on.
  10. hmm keep us posted, this is new by me and would love to hear how it all goes. 
  11. #51 Langalier, Sep 19, 2013
    Last edited by a moderator: Sep 22, 2013
    I have discovered a much less expensive method of trapping Fungus Gnats than those yellow sticky tapes.  When my spouse buys fish from the market it comes in white styrofoam trays. Simply fill these white trays with about 1/2 inch of water,  tap in a few drops of yellow food coloring, stir and place amongst the plants.  When the little F#%@&#S land on the surface, not being seagulls they are unable to take off again. Works as well as sticky tapes or better (larger surface area) at virtually no cost. Then once a day I dump the water refill with fresh, a couple good drops of food coloring and your set. I replace daily to judge how well the control is working. The humidity increase ia a helpful bonus.
  12. I've put the yellow sticky cards in each pot, and they've been of little to no use.  Even the most infested plant doesn't have all that many gnats on the card after two or three weeks.
    The cinnamon I mixed with the dirt doesn't seem to have been effective either.
    So I ordered Gnatrol.  The definitive move would be to soak the dirt with the Gnatrol solution to kill larvae, then haul the plants into a bathroom and set off a fogger to kill the adults.  I'll keep you posted.
  13. So thankful for everyone's input on this problem! I am still infested though, and they are positively RELENTLESS!!! I suddenly have an influx of them,  even though I've got my apple cider vinegar traps that catch MANY (besides the fact that I literally derive JOY out of killing the little F*%#ERS and do it over and over and over again)!! UGH!!!! I realize I am on a grower site (cuz you guys have the best input I've found so far on this topic), but I have ZERO plants growing in my house, NOR do I have rotten fruit, vegetables, or ANY food or dirty dishes or old garbage sitting out! We live in an apartment and have been plaqued with these bastards since we moved in~~I've never seen anything like it! Sure, they came and sprayed, but they are NOT addressing the situation, so I'm basically screwed. (I've come to believe that they come from deep within the sewer system, or some rotting place in the floor somewhere which is completely undetectable, or the vents posibly...who knows?!) I've tried incessantly to pinpoint exactly where they come from, but they are everywhere, not just one place!!! I mean, it's quite literally like Chinese torture sometimes! I've tried pouring copious amounts of boiling water down all the drains (I don't use bleach or any harsh chemicals), but to no avail. Besides, even though the sewage system is one of my theories, I never ever actually see them hanging around the drains! MAN this has been frustrating!!! Just letting you guys know in case anyone at all might have further input on these demons from hell. I guess I should just be thankful that they do not bite, but omg, I am OVER THEM!!! :confused: :eek: :cry:
  14. I dont know if anyone is gonna read this but, I mixed the hydrogen peroxide with water and sprayed the soil with a spray bottle, I sprayd alot but idk if the plant was completley dry.. I didn give it water for like 2 days, will the solution still kill the little fuckers or will they live because the soil was still damp

  15. They still lived when I watered with a diluted h2o2 mix but I talked to my local garden store and what they said led me to believe that these are more of a nuisance than anything.  I don't think they cause much damage, I had them throughout the grow last time and still enjoyed nice results, aside from all the gnats i had to pick off the buds since they get stuck to the trichs.
  16. Thanks for the usefull info,i just had one question,i dont have alot of money n cant afford to buy large amounts of hydrogen peroxide,so would it be ok to just make up a solution which would soak only the top 2 inches of my soil rather than making a heap up n doing a soil drench?
  17. "simply give them a sticky yellow surface to land on, and within a few days you'll have enough dead adults to make a tasty dinner of gnat casserole"
    OK, that has not turned out to be true or useful.
    And didn't someone try the hydrogen peroxide and found it to be ineffective?
    The most recent thing I've tried is sand.  I covered the entire surface of the dirt with a half-inch of beach sand, and so far it has been pretty effective.  The challenge is watering the plant without exposing the underlying dirt; I need a gentler way to pour the water over the sand to it doesn't push the sand aside and stir up dirt.
  18. So. I'm growing organic... The thought of this bugs me, but what I'm gonna do is cover the soil with panty hose material and water after fully dried (alnost) *just watered yesterday* with RO water I just bought a gallon of for this specifically.... Added 1 3/4 tsp per gallon.

    Should I need more? 3% btw.

    The gnats seem okay but those larvae are killing me and I know it. Subtle things just keep adding up bit by bit with no other explanation!

    But... I've only seen like 3 gnats.

    I just put out 3 vinegar traps. Hope that helps. I'm just desperate to fix this so using H2O2 seems to be the best bet because it kills instantly and oxygenates roots... Even though it kills beneficial bacteria as well, I'm just going to bite the bullet and add more mychorrizae after I water.

    Does anyone know of H2O2 has any effect on organic nutrients and their uptake? pH isn't a huge concern because it's easily fixed.... Just need the info here!



    Everything seen here is taken from sources online and in No WAY is this real at all. These posts are purely for entertainment value only and hold NO truth.
  19. Didn't people already confirm that hydrogen peroxide doesn't work?
    I put a layer of sand over the dirt in my plants.  This pretty much eradicated the gnats, but now I have small moths and mealybugs on one of my plants.
    These plants are turning out to be a pain in the ass.
  20. All I did was stretch panty hose material over the soil and top of the pot and put out 3 little vinegar traps.

    Also. Used the potato slices... This allows you to throw these little larvae away by the truck load!

    So. Yea. Deff not going to totally destroy my soil with H2O2! =)

    Everything seen here is taken from sources online and in No WAY is this real at all. These posts are purely for entertainment value only and hold NO truth.

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