Frass (insect excrement) deposited on leaves, flowers, or produce causing visible blemishes, particularly problematic in ornamentals, lettuce, and herbs.

Potential transmission of plant pathogens via movement across algal and decaying surfaces to crop tissues.

High populations create unpleasant working conditions for greenhouse staff.

In severe infestations, frass accumulation on young plants or cuttings can reduce photosynthesis and hinder growth. Affected plants may become unsellable due to visual contamination.

The shore fly undergoes a complete metamorphosis consisting of five stages: egg, three larval instars, pupa, and adult. Eggs are laid singly in damp organic matter, particularly where algae is present. They are bean-shaped and difficult to see with the naked eye. The first instar larvae are translucent white and very small. As they develop into the second and third instars, they become more cylindrical and brownish in color. These larvae feed and pupate in the top layer of moist substrate.

Adult shore flies are compact and robust, measuring approximately 4–5 mm in length. They are black-bodied with short legs and antennae, and they possess large, prominent eyes. The wings are marked with distinct grey-brown patches, which help distinguish them from other small flies. While sometimes confused with sciarid (fungus) flies such as Bradysia paupera or Lycoriella ingenua, shore flies are more stoutly built and lack the bead-like segments on their antennae characteristic of sciarids.

Managing shore flies (Scatella tenuicosta) effectively starts with addressing the environmental and cultural conditions that support their development. While these pests don’t feed directly on plants, their presence is closely tied to excess moisture, algae growth, and high levels of organic matter—often signaling underlying issues in the crop production environment.

Address Underlying Issues First: Shore fly infestations typically point to excessive algae growth or, less commonly, fungal growth triggered by the overuse of organic fertilizers. Before implementing any pest control strategy, identify and correct the root cause—whether it's high humidity, poor sanitation, or excess nutrients. A proactive inspection and adjustment of growing practices is essential.

Dry Backs in the Watering Cycle: Shore fly eggs and larvae rely on consistently algae environments to survive. By allowing the growing medium to dry out between waterings (a practice known as dry backs), you reduce the survival of eggs and deter females from ovipositing, as this removes a key food source and breeding site.

Remove Affected Plants: Plants with root rot or other signs of severe stress should be removed promptly. Decomposing plant material offers a food source for larvae and supports the growth of algae and pathogenic fungi, accelerating pest population growth and disease spread.

Treat Floor Drains: Floor drains are a common but overlooked source of re-infestation. Shore flies can breed in the moisture and organic biofilm that accumulates in these areas. Regularly clean and treat drains with acids, hydrogen peroxide (H₂O₂), or appropriate cleaning agents to kill pests and disrupt their breeding cycle.

Reduce Moisture in and Around Production Zones: Focus on eliminating standing water under benches, in aisles, and along edges of the growing area. Improve drainage and airflow to keep these areas dry and inhospitable to shore flies and other moisture-loving insects.

By focusing on environmental correction and sanitation, growers can significantly reduce the likelihood of shore fly infestations and avoid the complications associated with their presence.

Once cultural and environmental conditions have been optimized to reduce shore fly (Scatella tenuicosta) pressure, biological control strategies can provide effective, sustainable population suppression—particularly when implemented preventatively and in conjunction with monitoring tools.

Capsanem (Steinernema carpocapsae): This entomopathogenic nematode is a proven biological control agent for shore fly larvae. When applied as a soil drench or through irrigation, Steinernema carpocapsae actively seeks out and enters larvae present in the top layers of damp growing media. Once inside the host, the nematode releases symbiotic bacteria that rapidly kill the insect, allowing the nematode to reproduce and continue its life cycle. Capsanem is most effective when applied to moist media and in areas where larvae are known to develop. Use regularly during periods of peak pest pressure or as a preventative in algae-prone zones.

Yellow Horiver Sticky Cards: These sticky traps are an essential component of any Integrated Pest Management (IPM) strategy. Adult shore flies are highly attracted to the yellow color and are captured on the sticky surface, reducing the breeding population and allowing growers to track pest pressure. Place sticky cards horizontally near the soil or substrate surface—especially in propagation zones, wet spots, or areas with visible algae—to monitor adult emergence and detect hot spots early. Replacing cards weekly ensures maximum efficacy and consistent data.

When used together, Capsanem and Yellow Horiver cards offer both active control (larval mortality) and passive population reduction (adult trapping), supporting long-term shore fly suppression in greenhouses and indoor grow facilities.