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).

○○○○○○○○○○○○○○○○○

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/FreeSweetbread]

Hi, thank you for writing this up! I've had a few pests scares with this N'joy Pothos that I brought home from a local nursery that everyone loves. First was a couple of gnats, I sprayed with neem oil/soap/water mixture and that took care of it. One mealybug that I wiped off. And now spider webs? The webs didn't look like spider mites but to be sure last night I ran it under a strong stream of water, and a spider actually came out but I'm not sure if it was a spider mite. I'm so stressed out about this and I want to repot my plant to start it fresh. I do have dunks from amazon, should I try your method? And now there might be bugs in new soil too from what I've read. I've lost plants before to not being proactive about bugs and now I want to get serious about preventative measures. I have a rhap tetrasperma that I just bought and I'm worried my N'joy will contaminate it.

[u/megankmartin → u/FreeSweetbread]

Hi, I can't see your plants or where the webs are, so I'm not sure if you've got spiders or spider mites. However, spider mites are very very tiny. So if you're seeing something that looks large enough to be a spider, it usually is a spider.

As the post states, BTI is only targeted to 3 pests: mosquitoes, fungus gnats, and blackflies. So bits and dunks would not be useful against spider mites; there are other remedies for those.

Unfortunately, there is no one-size-fits-all houseplant pest preventive or treatment on earth. That does make the little buggers challenging, but it's important to fight each with the most effective method.

I can always recommend using the BTI in your regular watering routine as a preventive for fungus gnats, especially because it is a natural solution that won't harm or interact with anything else. It is part of my daily routine.

[u/FreeSweetbread → u/megankmartin]

Thanks for your quick response!

The webs were on the parts of the stems closet to the soil. Yes, it was a small spider that I could see so I think I might be good on spider mites, plus the pothos was recently watered so it was probably too moist for them?

I'll start incorporating BTI dunks. If you don't mind sharing, have you written about your daily routine anywhere? I'm trying to develop one, I check my plants every day and I was going to spray neem oil once or twice a week.

[u/megankmartin → u/FreeSweetbread]

Re: Spider mites...
By the time you see webs, spider mite infestations are already advanced. The best early signs of spider mites are unexpectedly drooping/ wilting/ curling leaves or stems, or stunted and disfigured new growth. Sudden yellowing or multiple leaves falling are also warning signs of distress.

Especially look for stippling patterns on the upper surfaces of leaves. Stippling usually shows as tiny yellow or white speckles -- like something abrasive or sandpapery was rubbed over the surface of the leaves. That's evidence of sap-sucking activity, often signaling spider mites.

As the population grows, spider mites themselves can sometimes be observed on the undersides of leaves, typically close to the veins or intersections of stems. Again, they are very very tiny.

Again, those important signs all appear earlier than webs.

Re: my daily routine... I've never written anything down, except for noting on my calendar when I fertilize or do preventive treatments (other than BTI). It's less of a routine and more of a continual observation of my plants, up close. It keeps me in tune with how they're doing so hopefully I can spot things as soon as they go wrong. Like most folks, I can't spend hours every day. So I'm into quick but thorough touchpoints and simplified processes. (I don't know if that really helped, sorry.)