Fungus Gnats in Chinese Evergreen — Overwatering's Visible Consequence
Chinese Evergreen (Aglaonema commutatum (and related cultivars))
Symptoms
- small dark flies hovering around the pot or emerging from the soil
- flies present when the pot soil is disturbed
- larvae in the top inch of moist soil
- the plant showing mild wilting if the infestation is large enough for larvae to damage fine roots
Causes
Moist, peat-rich soil sustaining larval development
Chinese Evergreen is one of the plants most commonly associated with fungus gnat infestations, and the reason is the soil it is typically sold in. Peat-based mixes are high in the organic content that fungus gnat larvae (Bradysia species) feed on and retain moisture for precisely the period that larvae need to develop — 3–5 days of moist conditions in the top 2 inches. Growers who water Chinese Evergreen in its original nursery mix and keep the soil surface from drying adequately between waterings will frequently encounter gnats. The gnats confirm that the soil is staying too wet — and for Chinese Evergreen, that means overwatering risk.
How to Fix It
- 1
Push the watering interval out until the top 2 inches of the peat mix are genuinely dry, not just the surface crust — peat can look dry on top while staying damp underneath, so check by feel a couple inches down before rewatering.
- 2
Mix a Bti drench (2 tablespoons Mosquito Bits steeped 30 minutes in a quart of water, then strained) and use it in place of a normal watering; Chinese Evergreen's peat-heavy nursery mix tends to re-wet the top layer quickly, so stick with the full 7–10 day, 4–6 week cycle even if gnats seem to disappear early.
- 3
If the plant is in its original nursery peat mix: consider repotting into a better-draining mix that dries more predictably. This addresses both the gnat habitat and the overwatering risk simultaneously.
- 4
Place yellow sticky traps near the soil to capture adults and monitor population.
Prevention
- Repot Chinese Evergreen from nursery peat mix into a draining mix — this alone significantly reduces gnat risk
- Let three-quarters of the pot dry between waterings — the peat-heavy nursery mix stays gnat-friendly far longer than the surface crust suggests
Quick Summary
| Plant | Chinese Evergreen (Aglaonema commutatum (and related cultivars)) |
|---|---|
| Category | Pests |
| Likely causes | Moist, peat-rich soil sustaining larval development |
| Fix steps | 4 steps — see above |