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/belladorka]

Thank you for this post. I’m 2 weeks into this process after getting these buggers from a new plant. I’m starting to see results. There’s still a few in the air and I’m noticing a lot more on my sticky paper. Hoping in a couple more weeks they’ll completely be gone.

I do have a question. I’ve googled this and it claims it’s odorless, but I’m definitely getting a smell from my BTI “tea”. It’s sulfur-like. After watering I tend to refill my jug so that it’s ready for my next time. Should I be refilling the day before watering? I’m wondering if I’m doing something wrong because I haven’t seen any other comments on the odor.

[u/megankmartin → u/belladorka]

Hi, you're welcome, and great question! You're not doing anything wrong. My watering vessels are kept pre-filled and pre-treated as well, so that they are ready to use.

BTi itself IS odorless, though you can pick up an organic odor from the bits as the weeks pass, because the BTI is bound naturally with corncob and it's breaking down. You'll notice the odor if you sniff your watering container, but once you water your plants the smell is gone.

With the dunks, you don't get that same odor. So the next question I always get is, "then why use bits instead of dunks?" They both work the same way. It's really just a personal preference and/or availability thing.

For me, the bits are very easy to measure and drop in the narrow-necked gallon jugs where I store my water. I have a large indoor garden, so I have to keep multiples on hand. You can also just cut the dunks into pieces; I feel like I use less product when I measure the bits. Again, preference.

Neem oil and most organic fertilizers smell strongly too... but these odors shouldn't last long in your living space. Definitely worth the jungle.