Dalotia coriaria
A slender, dark brown rove beetle about 1/8 inch (3–4 mm) long, with wing cases so short that most of the abdomen shows. It is sold as Atheta and released in greenhouses and propagation, where adults and larvae hunt in the top of moist media and on wet benches. It eats fungus gnat larvae first, and also shore fly larvae and thrips pupae. Unlike a drench, it breeds on site and flies to new breeding spots, so it is put in early, before numbers build.
At a glance
- Mode
- Predator — adults and larvae
- Rate
- 0.1–2 /sq ft; suppliers differ
- Ships as
- Beetles in peat or vermiculite
- Temp
- 65–80 °F (18–27 °C) best
- Humidity
- 50–85 % RH (UConn)
- Egg to adult
- 17 days at 79 °F (26 °C)
How it works
Adults and larvae are both predators. UConn describes them as generalists that prefer fungus gnat larvae and also take shore flies and thrips pupae in the growing media; suppliers add springtails, moth fly larvae and root mealybug crawlers. They live in the media, in cracks and crevices, and around algae and decaying material where that prey breeds. Suppliers put consumption at 10–20 prey a day, and a Dutch trial found adults ate 50–87% of the eggs of a caterpillar pest of potted plants.
What sets it apart from the other soil biologicals is that it stays and spreads. Adults fly, so they colonise a house from the release points, and once established UConn says they are there year round, rising and falling with the gnats. Egg to adult takes about 17 days at 79 °F (26 °C), or 21 days at 70 °F (21 °C); UConn gives females about 90 eggs and some 48 days of life, though an older Rincon-Vitova bulletin says adults live 21 days. That slow build is why it goes in at the start of a crop, often alongside the faster soil mite Stratiolaelaps scimitus.
Is it established?
The beetles hide in the media, so you see them by looking for them, not by chance. Check the same spots each week, and keep reading yellow cards for the pest.
- DAY 1Adults running over the media near the release piles, or flying off when disturbed
- WEEK 1First cream-coloured larvae in the top of the media; eggs hatch in 3–4 days
- WEEKS 1–2Supplier guidance: a visible downward trend in fungus gnat and shore fly numbers on yellow cards
- WEEKS 3+A new generation of adults, egg to adult in 17–21 days; beetles now found away from release points
What it is confused with
It is one member of a large family: the rove beetles that turn up on their own in compost, leaf litter and under pots look much the same and are just as welcome.
- Also goodWild rove beetles — Same body plan — short wing cases that leave most of the abdomen bare. They hunt in the same damp media and debris; leave them.
- PestFungus gnat and shore fly adults — Both are flies with one pair of wings. The beetle runs over the media and has hard, short wing cases.
Release & handling
Beetles arrive as adults (some suppliers add larvae) in a tube or bucket of peat or vermiculite, shipped overnight. Release them the day they arrive. The Koppert distributor allows one to two days in a cool, dark place at most; an older Rincon-Vitova bulletin allows up to seven days at 50 °F (10 °C). Adults fly, so open the container only where you mean to release them.
Release the same day
If you must hold them, keep them cool and dark. Suppliers differ on how long: one to two days (Koppert) up to seven at 50 °F (Rincon-Vitova).
At dusk, onto moist media
Adults are nocturnal. Water beforehand, not right before release, and wait a few hours before watering again (Sound Horticulture).
Small piles where flies breed
Onto pots, capillary matting, algae patches, under benches and on dirt floors. Rincon-Vitova suggests 50–100 in one spot to make sure they mate.
Consider a breeder box
A bucket of media and supplier food under a shaded bench keeps a population going with only occasional top-ups (UConn, Clemson).
Pesticide sensitivity
In growing-media trials, clothianidin, dinotefuran and thiamethoxam drenches killed almost all adults, and chlorpyrifos and chlorfenpyr most of them (Cloyd et al. 2009). Acetamiprid, lambda-cyhalothrin and cyfluthrin were also harmful (Echegaray & Cloyd 2012). Bti, flonicamid, spinosad, azadirachtin and Metarhizium were not toxic to adults, nor was Beauveria, though it cut how much they ate. Third-instar larvae were three times more susceptible than adults to insect-parasitic nematodes; Steinernema carpocapsae and S. riobrave killed the most, and S. feltiae and Heterorhabditis bacteriophora look the most compatible (Tourtois & Grieshop 2015). Check a product →
When to choose something else
It is a standing, preventive predator for wet greenhouse and propagation benches. Look elsewhere when:
- Shore fly larvae are in standing water — UMass says the beetle will not reach them there; fix the drainage and clear the algae first
- Larvae are already doing damage and you need a fast knockdown — drench with Steinernema feltiae
- You want the quickest start at potting — the soil mite Stratiolaelaps scimitus establishes faster, and suppliers advise using both
- The media floods or the house freezes — Rincon-Vitova says the beetle survives neither
- Your program relies on neonicotinoid drenches — clothianidin, dinotefuran and thiamethoxam in the media killed almost all adults in trials
Where to buy
Suppliers listed alphabetically, not ranked. helpfulbugs takes no commission and does not sell insects.
- Arbico Organics500 / 1,000 / 3,000 / 5,000US
- Buglogical500 / 1,000 / 3,000 / 5,000US
- Koppert (Atheta)1,000 / 5,000US / CA
- Sound Horticulture100 to 5,000US
Dalotia coriaria by target
Rate and timing differ by what you are releasing it against. Each page below is the program for one pest.