Gnat or fruit fly larvae

Is there a best way to flush the soil to kill the larvae? I’ve used a 1-4 solution of hydrogen peroxide. Can I use stronger strength or is there any kind of sure thing?

As always thanks to everybody

Don’t know why yopu used Hydrogen peroxide???

I will look into getting you a couple links for products. This is what I use.



Lot of stuff out there about peroxide. Wish I had known not to use it

Late I use the DE they don’t stay away. Any other advise or is that about it? thank you so much

Sorry; Ever since I used DE; I have not had a spider mite or anything else in the room. This is a suitable for pest control:


Thank you for dedication to helping people. These little bugs drive me nuts. Thanks late!

Are you being careful to not over-water? The fungus gnat larva usually need very wet soil to survive, as well as the soil fungus that is a result of over-watered plants. They can start eating the fine root hairs and even the roots themselves if they get too out of hand.

I’ve heard most spray and topical pesticides may not work very well on fungus gnats.

Make sure you don’t have pooling water or wet decomposing plant material anywhere as well, they need the moisture and decomposition for food and to survive. Decomposing plant material might include drowned decomposing roots you can’t really see. Use the “water only when the soil container feels very light” as if all the water that would make the soil heavy is gone, and only water when the soil is nearly totally dried out.

Thanks MacG, I might be a little heavy-handed on the watering. I’m going to practice letting the soil dry all the way out before watering. Better to let the plants Droop A little then to risk oversaturated bug infested soil, yes? Thank you

You should notice the plant’s container feels very light, even before the leaves droop. That, along with looking for the slightest hint of leaf droop, and soon you’ll know when to water even before any droop is noticeable to most people and you’ll have very happy healthy plants.

Also, re-apply the DE to the surface of the soil immediately if you haven’t already done so, and right before watering the next few times you water.

You need to keep the future generations under control, until all eggs in the soil have hatched and have not been able to survive to adulthood to repopulate the soil with more larva.

It is only the soft larva stage in the soil that are really affected by the DE. The adults fly around and only land on the soil to lay eggs, and DE is not fast acting at all on the adults, and the adult life-cycle of the fungus gnat is pretty short, they mostly just breed, lay eggs, and die.

The adults usually don’t do much other damage – like eating any of the plant’s parts during the adult stage, however they can spread fungal spores to other parts of the plant and can contribute to things like bud rot.

The eggs that are already in the soil seem to be impervious to the DE as well, it isn’t until it hatches and the larva emerges into the soil – will the DE work to kill the larva. You have to make sure there is enough of the DE sticking around and not just being washed out the bottom, so it is still there until all the last eggs have hatched.

Happy growing,


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Great advice: After a couple times watering and manually weighing the pot afterward; And waiting until it is real light before watering again; It will start come naturally. :slight_smile:

I drilled some holes in the plastic pot in the soil was soaking wet at the bottom. I drilled lots of holes to help dry out the soil. I’ll put a lot of DE on the top I left the soil dry out completely. This is one of three clones I removed from my outdoor greenhouse and put in the garage. For some reason this plant just wasn’t draining I’m half tempted to repot it. Not sure how long it will take to dry it out I’m just using for LED tube lights to try to flower these three plants.

Wow every day its something. Thanks for your help Roger

Right you are rcknrog11, there are always things going on that you have to be aware of to head off problems. Are you a new grower? I had that lost feeling my last grow (my first ever indoor grow and my first grow in 30 years. Needless to say, studying hard was on my list as it seems like something, no matter how little, popped up every day. Between all the help here and studying, I have managed to pick up a lot of problems. If you know early symptoms, you can head off the problems. Asking questions is nice but really studying in a book or online will, for most people, make the problem ,much clearer. If that doesn’t help, the support staff is awesome.

ILGM is great for information and their seeds are TOP LINE! Grow such beautiful plants that I cannot believe it when I look back at my grow log and pictures. Good luck with your grows and Great Buds for you.


Thanks for the message Txman yea I’m new, I also hate studying. Pretty sure overwatering has been my worst enemy. I have three plants I’m trying to flower in my garage, that’s where the knat problem is and they are in soil . I have 12 in a outdoor greenhouse that are a a month old all from og kush seeds. They are in pro mix soilless medium in smart pots. I think if I get the overwatering corrected along with the nutes I will have better success. I’ve included a pic of the lil GH



Nice greenhouse rcknrog11 must have an awesome view…lol
Glad to hear that you have solved your problem. I hope your onto better times.

Be Safe

That is a rockin’ greenhouse! Looks like it is well hidden also!

I would LOVE to start an outdoor grow but it is not legal here and there is no place to hide it. Where I used to live (Northeast US) it was perfect to be able to cammo a grow and never have any problems. It would have been killer to have a Robert’s genetics then !

I believe over/under watering is the number one problem of nearly EVERYONE’s first grow. We are fixated on doing all these things to make the plants skyrocket, and forget that genetics will drive a plant to a good grow without us interfering. All we can hope to do is little touches here and there to let the plant flourish.

If studying is not your thing, nothing to be ashamed of, you can learn a lot from the support blog. I believe the really big things are, besides over/under watering, keeping pH in a good range, watch your PPM and do NOT over fertilize. If you follow the first two (pH and PPM) the third should follow right along.

Good Luck on your grow. I would recommend that you get all the vital info of your grow written down in case you have a problem. (Light intensity, Nutrients, pH of water, type of medium and many other things.) It helps out immensely to figure out what your plant has been exposed to. There is a list that is at the top of the support site that works well in assisting the staff in helping with your problems.

Good Luck and Great Buds

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You are welcome. Another tip is to buy some yellow paper sticky traps to hang about the greenhouse.

Five and a half week og kush seedlings.

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rcknrog11 Very nice looking ladies! You are definitely giving those ladies a lot of TLC ! ! Keep us up to your progress. That looks like it is going to be a nice harvest !


Just thought I would post a few current iPhone shots of the greenhouse with the sunset and the plants with buds on them. It is pretty damn exciting to see flowers on these plants I really haven’t had a bug problem with the 12 plants that I have in the greenhouse it’s a lot of fun I have been off the board for a little while but again thanks for all the help I have always received here Roger

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Looking really nice. How long till harvest ? Looks like they are close !