SUMMARY of BugBites! Session 5: Fungus Gnats and Shore Flies

Review Part 2: Shore Fly Management

While shore files (Ephydridae) are primarily seen as a nuisance in protected production spaces, they can also degrade the quality of your plants. Adults are known to leave 'fly vomit' behind as they make their way through the production space. These small black specks can be found on plant parts and growing surfaces, and are no aesthetic addition to your pristine green canopies. 

The following information is a summary of session 5 of the BugBites Series: Fungus Gnats and Shorefly Suppression with Beneficial Organisms. To watch the full session, click here! 

Pest Description: 

Adult shore flies, although similar in size to a fungus gnat, are comparable to regular house flies in appearance. These insects can be identified by the 5 white spots on their wings. 

Larvae are semi-aquatic, which can be identified by their Y-shaped breathing tubes. The larvae are semi-aquatic in nature, and can range from cream-coloured to brown.  

Monitoring and Scouting: 

Traditional yellow sticky cards are effective for monitoring and catching adult shore flies. These insects are much stronger fliers compared to fungus gnats, so placement of the yellow sticky cards right at the soil line is less critical. 

Biological Control Options: 

The best method for managing shore fly populations is to manage algae build-up around the facility. The larvae, which are semi-aquatic, rely on algae as their food source. By removing a key part of their reproductive cycle, pest population sizes will be limited. The best way to manage algae is to repair any leaky points along the irrigation system, and carefully sloped surfaces to keep water from pooling. 

Next is insect management. By conducting regular scouting checks of the crop, and maintaining populations of biological control agents, you can limit the degree of pest infestation.

Dalotia coriaria; Rove beetle

• Predator to both shoreflies and fungus gnats
• Both adults and larvae are predatory
• Orange larvae are noticeable in the soil
• Adults readily move around via flight
• Ready establish in greenhouses
• Works well in hydroponic systems

Figure 2. A photo of a rove beetle in the adult (left) and larval (right) stages. stuck to a yellow sticky card.  Image taken from the BugBites! Session 5 presentation

The use of rearing boxes allows for a slow-release approach, and will help maintain beetle populations through the season. Rearing boxes can be as basic as media (ex. peat, vermiculite) set inside a Tupperware container, and supplemented with food (ex dog or fish food, artemia). It is crucial to keep this moist, but not wet. These can be placed under benches.

Steinernema feltiae; entemopathogenic nematode

• Target fungus gnats, shoreflies, thrips pupae and many others
• Forage in the top inch or two of the soil
• Water into your growing media lightly- if they get too far in, they will not be able to combat pest populations
• Not highly mobile
• 50-78F are ideal conditions
• Well suited for greenhouse environments
• Susceptible to being washed away in rockwool
• When growing in rockwool, apply after the last irrigation of the day to give them a chance to establish

Steinernema carpocapsae, entemopathogenic nematode

• Target shore flies, and thrips pupae
• Good at finding mobile pests
• No problem working in/establishing on rockwool
• Lives on soil surface (use very little water when applying to prevent from washing them too deep into the growing media)
• Ideal temp is 57-84
• well suited for greenhouse environments

* Both nematodes listed here can be applied together, since they focus on different parts of the soil.

The key for management here is prevention. By adding nematodes and rove beetles into your production routine, and managing algae growth around the facility, shore fly populations should be significantly reduced. 

Posted by: Talia Plaskett