Fungus Gnats on string of pearls
What's Happening
Fungus gnats (Bradysia spp.) infest String of Pearls when soil remains moist for extended periods, particularly in propagation pots where cuttings retain moisture longer than established plants. The larvae feed on organic matter in soil and can damage the shallow, fibrous root system if populations grow unchecked. Adult gnats emerge first, but their presence indicates active larval colonies in the rhizosphere.
How to Fix It
- 1
Monitor population: Deploy yellow sticky traps at soil level to capture adult gnats and assess infestation severity
- 2
Mechanical removal: Use vacuum cleaner hose attachment after gently agitating soil surface to flush out adult gnats; repeat daily until population declines
- 3
Larval control: Apply food-grade diatomaceous earth (DE) as top-dressing to soil surface; DE dehydrates larvae and pupae on contact
- 4
Soil drench option: Treat with neem oil or 3% hydrogen peroxide diluted 1:4 with water applied as soil drench to target larvae; repeat weekly for 3 weeks
- 5
Biological control: Introduce beneficial nematodes (Steinernema feltiae) to soil to parasitize gnat larvae
- 6
Dry-out protocol: Allow top 2-3 inches of soil to dry completely between waterings to break gnat life cycle which requires moist conditions for reproduction
How to Prevent It
Use gritty, fast-draining succulent mix with minimum 50% perlite or pumice to prevent moisture retention. Allow soil to dry completely between waterings—typically 2-3 weeks indoors. Elevate pots on feet or pebble trays to improve airflow beneath containers.