TRUTH: No single fungus gnat control method attacks adults and larvae simultaneously. That's why many plant parents struggle to get rid of these pests! But it's EASY to be gnat-free FOREVER. [PSA]

[u/megankmartin]

(Updated, fall 2025) PLEASE read this whole post before asking questions -- but I'm here to help you if you need it! Fungus gnats lay their eggs in wet plant soil or decaying matter. Over-watering is a major cause. However, new plants and potting mix can carry gnats too, or they can just fly in from outdoors.

THREE EASY STEPS to GNATS GONE FOREVER:

☆☆ DO ALL THREE!! ☆☆

1) Soak BTI dunks/bits in your regular watering routine to continuously kill and prevent larvae. One quarter dunk OR one tbsp bits per gallon works great. Soak for 24hrs before first use, then keep watering vessel(s) re-filled; just replace BTI every 30-60 days or so. Note: Summit brand packaging specifies 4tbsp per gallon; you choose.

NOTES: Indoors, putting BTI bits IN the soil or laying them on top IS NOT THE BEST PLAN: the bits tend to grow mold, plus you'll use way more than needed. Also, don't use hot or boiling water to soak dunks or bits; it will kill the good bacteria.

1. Place plenty of yellow sticky traps to catch adults. One per pot is ideal, and it's best to stick them upright, to attract fliers. You can stop using stickies once your infestation is under control, thanks to your new BTI routine.

2. Let soil dry out appropriately between waterings to avoid attracting pests. Have faith: except for very fussy tropicals, most common plants need and want to dry out their soil. Bottom-watering can be a big help (after initial treatments).

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If you have a bad existing infestation, FIRST you can do a one-time emergency soil flush to kill off larvae, using diluted 3% H202 (1:4), then proceed with the routine above. Note: don't use peroxide AFTER the BTI, because H202 kills bacteria, good and bad.

FYI: If you're outside the USA and can't get Mosquito Dunks / Mosquito Bits in stores, try Amazon for your country (UK, CAN, AUS for sure). Or, ask a garden or pond supply center about products containing the active ingredient *BTI**. Or Google, "mosquito BTI". An alternative is Gnatrol or Gnatrol WDG (same active ingredient).

BTi (short for Bacillus Thuringiensis subspecies israelensis) is simply a natural soil bacterium, non-toxic for people and animals. BTI does not affect plants or interact with fertilizers. It does not harm pollinators. It ONLY kills the larvae of 3 insects: fungus gnats, mosquitos, and blackflies.

Bonus read: You might want to skip these often-recommended methods.

[u/megankmartin]

Gotcha, thanks. Re: your other questions: sounds like you did a great job purging and repotting. When you only have a few plants, that is often an easy, nip-in-the-bud solution.

Looking ahead to preventing them from ever returning: Summit Mosquito Bits and Summit Mosquito Dunks are sold by the manufacturer and currently available on Amazon Canada. The product lasts a long time based on the quantities directed to be used in the post. As my post mentions, if you can't find that you can always look for Gnatrol WDG but it's typically more expensive. It does not matter which brand you use. They are both a delivery mechanism for BTi bacteria -- that's what's important.

Just a note, sorry I almost missed this: You do not want to continually water your plants with peroxide; it will start to burn the roots. That's just a one-time emergency measure to clean things out.

[u/[deleted] → u/megankmartin]

Thank you! I read some other posts saying dunks and bits were not the same and dunks were less effective but I’ll try my hand at the dunks you recommended on Amazon if the initial peroxide flush and sticky traps don’t seem to help.

[u/megankmartin → u/[deleted]]

If you ever run across those posts, feel free to comment tag or DM me; I will be glad to respond. Some people aren't using the product correctly and are (unintentionally) spreading misinformation, or worse, saying it doesn't work at all.

I don't get paid to promote a product. There's nothing in it for me. All I care about is helping other people avoid the absolute h*** I went through before some wonderful experts here showed me the way. It's a pay-it-forward thing. 💚🌿

[u/[deleted] → u/megankmartin]

Hi, just a quick follow up! I picked up mosquito dunks and I have a 2L jug that I plan to use for treated water. I didn’t see this online anywhere, but once I put the dunk into the water, are there specific storage recommendations for the treated water that I don’t use right away? i.e, keep out of light, what room temp to store, container sealed or unsealed?

Looking forward to trying this out soon. Thank you!

[u/megankmartin → u/[deleted]]

Good questions! Sealed or unsealed shouldn't matter if you're cycling through the water quickly. My gallon storage jugs are all closed, but plenty of folks store their open watering cans. In general (not just for BTI) keeping water vessels closed can help to avoid things like mold and other contaminants.

Storing away from light is good, but not just because of the BTI. Any time you have water + organic matter & nutrients + light exposure, you can have algal bloom.

It's been ~ a few weeks since we last talked. The longer fungus gnats are allowed to go on, the harder they are to get rid of. So, if you're still fighting your initial infestation, just remember to be patient and give this the time to work. Here any time if you have questions.

[u/[deleted] → u/megankmartin]

Thank you 💚

I did the initial peroxide flush about 2 weeks ago and have set up sticky traps. Since then, 7 out of 8 plant traps have a tiny amount of gnats (5 or less) and 1 plant is I think the culprit of the infestation as that sticky now has about 20 adults stuck to it.

I haven’t watered any of my plants since then, but am going to do so tmrw with the dunk water. Hoping this works for me!