Greenhouse IPM scouting, incoming-plant inspection, sticky-card monitoring, fungus gnat and shore-fly differentiation context, hotspot mapping, recordkeeping, and treatment-effectiveness review.
Arthropod pests
Shore Flies
Shore flies are small dark flies associated with algae and persistently wet greenhouse surfaces. Adults are primarily a monitoring and sanitation signal rather than a direct plant-feeding pest, so they should be distinguished from fungus gnats before management decisions are made.
What to look for
- Small dark flies resting or running on wet benches, floors, media surfaces, and areas with algae
- Adults with a robust, small-housefly-like profile, very short antennae, and dark wings with several pale spots
- Larvae associated with algae-rich wet surfaces rather than feeding inside healthy roots
- Persistent populations concentrated where drainage, leaks, or chronic surface moisture support algal growth
Important look-alikes
- Fungus gnat adults and larvae
- Other small flies attracted to moist organic material
- Root-zone decline caused by overwatering or pathogens that happens to occur where flies are present
How to confirm
- Inspect adults with magnification instead of identifying from flight behavior alone
- Compare larval morphology with fungus gnat larvae when immature stages are present
- Map captures and sightings against algae, drainage, and wet-surface hotspots
- Inspect plant roots separately before attributing crop decline to the flies
Management principles
- Correct persistent moisture and algae sources that support reproduction
- Use sanitation and drainage correction as the foundation of control
- Treat shore-fly presence as evidence to inspect the production environment rather than proof of root feeding
- Re-scout wet areas after corrective work to verify that populations are declining
Prevention
- Prevent chronic standing water and algae buildup
- Clean benches, floors, drains, and media spills
- Maintain drainage and irrigation systems so surfaces can dry appropriately
- Include low, wet greenhouse zones in routine scouting
Visual study guide
- Shore fly versus fungus gnat adult comparison
- Shore fly versus fungus gnat larva comparison
- Algae and wet-surface hotspot map
- Drainage and sanitation inspection diagram
Evidence & further reading
Sources connected to this lesson
These references support specific biological, diagnostic, environmental, or process concepts used in this lesson. They are not a substitute for crop-specific testing or local regulatory guidance.Greenhouse IPM principles, plant quarantine, scouting, monitoring, sanitation, media, and integrated pest-management practices.