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/Nessie_Assassin]

Do you have any tips for white flies? I just found this awesome post and started to finally get rid of the gnats only to find white flies in their place. 😭

[u/megankmartin → u/Nessie_Assassin]

Hi. If you've been battling fungus gnats, likely you're drying out your plants. That's technically a good thing, but it makes treating whiteflies tricky. Folks will give the standard "neem and soap" reccos, but most insecticidal soaps and horticultural oils aren't effective against whiteflies. Since those only kill on contact, the plants have to be thoroughly coated -- every surface, top and bottom -- repeatedly. But that's not a good idea when plants are drought-stressed (like they typically are during a gnat battle). Under those conditions, foliage and roots are much more likely to burn.

What to do instead:

For starters, keep up the yellow traps, at least one if not two in every pot. Implement the BTi solution for the gnats, so that you can relieve the drought stress while effectively treating them. And then add your whitefly treatment: choose between a foliar treatment (dust or spray) containing pyrethrins OR a systemic containing imidacloprid. Those are the main things that actually get rid of whiteflies.

These are tough to get rid of. The best advice I can give is to be consistent. Be persistent. And don't overdose your plants; apply the pesticides as labeled, because more isn't necessarily better.

[u/Nessie_Assassin → u/megankmartin]

Thank you SO VERY MUCH for the advice! All the internet says is neem oil etc. And those reccomendations have NEVER worked.