Arthropod pests
Fungus Gnats
Small flies associated with moist organic substrates. Adults are primarily a monitoring nuisance; larvae inhabit the root zone and can feed on fungi, organic matter, and tender roots, with the greatest concern in seedlings and stressed plants.
What to look for
- Small dark adults running or flying near the substrate surface
- Larvae that are translucent to whitish with a dark head capsule
- Persistent surface moisture or organic buildup
- Weak seedlings or root injury when larval pressure is high
Important look-alikes
- Shore flies
- Other small flies
- Root decline caused by overwatering or pathogens without gnats
How to confirm
- Use sticky cards to monitor adults
- Inspect the upper root zone or use a simple larval monitoring method
- Distinguish larvae morphologically rather than assuming every small fly is a fungus gnat
Management principles
- Correct chronic excess moisture where compatible with crop needs
- Reduce algae and decomposing organic material
- Use an integrated larval-management program when populations justify action
Prevention
- Avoid continuously saturated surfaces
- Clean spills and plant debris
- Quarantine infested media or plants
- Monitor propagation areas closely
Visual study guide
- Adult versus shore-fly comparison
- Larva microscope plate
- Root-zone lifecycle diagram
- Sticky-card monitoring guide