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Dalotia (Dalotia coriaria, previously Atheta coriaria) - fungus, gnat, shore fly and thrips predator

Target pests: Fungus gnats (eggs and immature stages), Bradysia spp.; shore flies (eggs and larvae), Scatella spp.; and thrips (larvae and pupae) at ground level, including onion thrips, Thrips tabaci, western flower thrips, Frankliniella occidentalis, and plague thrips, Thrips imaginis

Dalotia

Dalotia coriaria is a small, soil-dwelling rove beetle which is a useful predator of fungus gnats, shore flies and thrips. It was originally developed as a biocontrol agent in Canada, and was discovered to be naturalised in many other countries, including Australia.

It is a voracious feeder with good potential also against manure flies, mushroom flies, fruit flies, and Carpophilus beetles. It has been reported feeding on root aphids and root mealybugs. Thrips may not be predated if preferred food sources are available.

Dalotia is supplied in a cocopeat and vermiculite medium that contains approximately 500 individuals of mixed life stages. Food granules sufficient to maintain larvae for a few days are also present.

Life history and biology

Adult Dalotia coriaria are 3-4 mm long, glossy dark brown to black, elongate beetles. The upper wing covers are short, exposing the segmented abdomen. The clear lower wings are unfolded when the beetle flies. It is this capability which makes Dalotia very mobile and a good coloniser within the greenhouse. A characteristic of rove beetles is that the adult curves its abdomen upwards like a scorpion when running or disturbed, but it is harmless to people. Small white eggs are laid into the growing medium. They hatch into pale larvae, which go through three growth stages which become a darker yellowish-brown. Larvae are also highly predaceous. Pupae are rarely observed, but are encased in a silk net woven by the final larval stage. There are equal numbers of males and females. The life cycle has been reported at approximately 13 days at an optimal 27°C, and 21 days at 21°C, although this appears to vary between populations from different countries. It is effective over the temperature range 12-35°C. Adults can live for 3 weeks, and lay 150-190 eggs, about 8 eggs per day during peak egg laying. An adult female reportedly can consume 10-20 larger prey or 150 fungus gnat eggs per day. Once established, populations generally persist all year in the greenhouse, and they do not hibernate under short day conditions.

Crop usage

: Most greenhouse crops are suitable for usage of Dalotia, including vegetables, ornamentals, pot plants, and propagation areas. They prefer a warm, humid environment, but will adjust to a variety of crop situations and media. They are particularly useful in cocopeat and capillary matting, and the ends of hydroponic guttering where algae grow and shore flies, moth flies and other nuisance flies breed.

Environmental preferences

Dalotia coriaria are attracted to decomposing plant or animal material and algae, so prefer these moist, warm environments where prey is most likely to be found. While this is usually within the upper layer of growing media, they have also been found in strawberry fruit and stone fruit damaged by Carpophilus beetles, feeding on eggs. They do not survive freezing or flooding, but otherwise adapt well to a variety of greenhouse growing conditions. They are more effective at lower temperatures than HYPOASPIS-S, but are not recommended below 12°C.

Application information

Storage and handling: Transport and store in darkness at 10-15°C. Dalotia is best used as soon as it is received. If necessary, containers may be held at 10°C for up to 7 days.

Release method(s): Dalotia should be released within the greenhouse during the cooler part of the day, by sprinkling the mix in small heaps onto moist media targeting areas where prey is known or likely to be present. Release evenly, but as beetles can fly distribution is not as critical as releasing predatory mites.

Timing of application: Due to its mobility and high consumption rate, Dalotia is best released when target pests are known to be present, or adults may leave the greenhouse to forage elsewhere.

Release rates: Apply at a general rate of 5 beetles/m2, and 10/m2 in hot spots. To ensure mating, release in batches of 50-100 beetles, in the centre of the greenhouse and in wetter areas likely to breed shore flies and fungus gnats. A second release is usually recommend 1-2 weeks later to ensure good establishment.

Monitoring control success

Assess adult fungus gnat, thrips and shore fly populations weekly using yellow sticky traps. Beetles may also be captured on these traps; if so, move the traps higher in the canopy. There will be a 2-6 week delay in any effect, because Dalotia does not eat adult pest stages. Look under pots and bags and in the upper 1-2 cm of moist media for larval and adult beetles. Cut slices of potato placed on the soil surface may attract fungus gnat larvae and Dalotia to the underside.

Tips for best results

Use a combination treatment of Cucumeris and Hypoaspis-M or Hypoaspis-A early in the crop, and Dalotia if pests are present in larger numbers. While Hypoaspis-S displaces Dalotia when confined in a small breeding unit, Dalotia has greater mobility and wetter habitat preferences which should ensure it persists in the greenhouse.

Quality control

Check Dalotia on arrival for live adults and larvae in the media. Dalotia adults fly and are very mobile, so do this in the greenhouse. Sprinkle some media on a white card to encourage movement. They will burrow quickly back into the media, or fly off searching for suitable habitats.

Pesticide compatibility

Dalotia coriaria may be affected by both foliar and soil-applied pesticides. Always check side-effects information before using pesticides or releasing Dalotia into a treated greenhouse. As a relatively new biocontrol agent, information is lacking on effects of many pesticides so caution is advised.

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Technical resources

Dalotia technical sheet (115 kb)