BTI vs Hydrogen Peroxide vs Diatomaceous Earth: Exact Dosages & Decision Flow for Homes

Fungus gnats show up like bad roommates: quiet at first, then suddenly every pot has a buzzing critic. You can swat the adults all day, but the larvae in the soil are doing the real damage—chewing fine roots, stressing plants, and prolonging the problem.

I wrote this because I got tired of half-answers: “use BTI,” “try peroxide,” “sprinkle DE.” Those are useful, but only if you know how much to use, when to repeat, and what to expect. Below you’ll find an evidence-based decision flow, exact dosages for common pot sizes, timelines, safety notes for edibles and pets, and three real apartment case studies with outcomes.

Read it like a playbook: decide what stage your infestation is at, pick the matching tool, follow the dosing chart, and don’t skip the follow-ups.

Quick overview: what each option actually does

• BTI (Bacillus thuringiensis israelensis): a biological larvicide. Larvae must ingest it. Safe for humans, pets, and beneficial insects when used correctly^[1].
• Hydrogen Peroxide (H2O2, 3%): chemical oxidation that kills larvae on contact and oxygenates the root zone. Fast, but can harm roots and soil microbes if overused^[2].
• Diatomaceous Earth (DE): a physical, abrasive powder that desiccates insects. Works well on adults and crawling larvae on the surface, but only while dry^[3].

Here's the simple rule I learned the hard way: target larvae directly and adults indirectly. Ignore either and the problem comes back.

The life-cycle reality: aim where it hurts

Fungus gnats lay eggs in moist, organic soil. Eggs hatch into larvae (the stage that eats roots), then pupate, then emerge as adults. Killing adults is satisfying. Killing larvae ends the infestation.

BTI targets larvae via ingestion. H2O2 kills larvae on contact during a drench. DE removes adults and surface active larvae. The best results come from combining these, timed correctly.

Exact dosages and application volumes (ready-to-use chart)

Use these recipes and volumes for common pots. All BTI dosages reference commercial granular products like Mosquito Bits/Mosquito Dunks; adjust if your product lists a different concentration.

BTI "Tea" (granules soaked, then used as watering liquid)

• Preparation: soak the stated granules in the water volume for at least 30 minutes (overnight is fine). Strain or let solids settle; pour the water into the watering can.

Pot Diameter	Water Volume to Use	BTI Granules (approx.)	Frequency
4–6 in	1 cup (250 mL)	1 teaspoon	Every 7 days for 3 weeks
8–10 in	1 quart (1 L)	1 tablespoon	Every 7 days for 3 weeks
12–18 in	1 gallon (4 L)	4 tablespoons	Every 7 days for 3 weeks
>18 in	Calculate soil volume; use 1 tbsp per liter of water	Adjust proportionally	Every 7 days for 3–4 weeks

H2O2 Drench (only 3% household peroxide)

• Mix: 1 part 3% H2O2 to 4 parts water (1:4 dilution).
• Applicat

---

References

---

Footnotes

1. Author. (Year). Title. Publication. ↩

2. Author. (Year). Title. Publication. ↩

3. Author. (Year). Title. Publication. ↩