Sciarid fly & Shore Fly control

Staphyline c

Atheta (Taxicera) coriaria

 

 

 

How does it work?

Atheta coriaria is a predatory beetle that has specialised in feeding on soil-dwelling larvae of small Diptera species. A. coriaria preferentially preys upon Sciarid and shore fly larvae and eggs, although thrips and other soil-dwelling insects may also be taken. The adults are 3-4mm in length and a brownish-black colour, whereas the larvae are thin and a pale yellowish white, darkening slightly in the later larval stages. These beetles are tolerant of a wide range of temperature, humidity, light, irrigation and soil conditions, making them suitable for year-round greenhouse use at lower temperatures than the predatory mite Hypoaspis miles. There has been no recorded diapause in this species at reduced light levels. Atheta coriaria is believed to have originated in Europe and has been recorded in North America, Australia, New Zealand, Chile and the Canary Islands. It may sometimes establish naturally in greenhouses in countries to which it is native.

A. coriaria develops from an egg to an adult in approximately 21 days, depending on temperature and food resources. It passes through three larval instars prior to pupation and adulthood. All larval instars, as well as the adults, are highly mobile predators. The winged adults, however, are better able to disperse and colonise new areas of infestation once the immediate prey is exhausted. Total development time decreases as temperature increases, although pupal mortality rises at higher temperatures. The normal life span and generation time is 21 days. Total development time from egg to adult is 16 days at 20ºC, 11 days at 25ºC and 10 days at fluctuating temperatures of between 23-35ºC (28ºC mean). Studies have shown the ideal temperature for establishment to be 26.7ºC, although higher temperatures encourage greater prey consumption. The lower threshold of egg to adult development is approximately 6ºC, although individuals can survive and actively feed at 4ºC in laboratory conditions. For commercial purposes, the lowest recommended temperature is 12ºC. Each female is reported to lay between 150 and 190 eggs at 21ºC, with a 50:50 male to female ratio. At 25º the doubling time for the population is 5.3 days, making this a quick-to-establish predator.

Mobile life stages of A. coriaria will kill and feed upon all developing stages of sciarid flies, although small-medium sized larvae are preferentially taken. Shore flies are also highly predated. Although initial published work suggests that and A. coriaria can contribute to thrips control, no such control has been seen in field trials. Laboratory studies have shown that of other prey species, Musca domestica and Carpophilus hemipterus were selectively predated. C. lugubris, C. humeralis, Haptoncus lutreolus and C. freemani were less preferred, although A. coriaria may switch prey if the relative abundance changes. This generalist behaviour partly accounts for the excellent establishment and persistence of this species in protected crop environments. A. coriaria will kill many more individuals than it consumes at high prey densities. The number of prey individuals taken depends on the life stage of the predator, prey and relative availability as well as temperature, but an adult Atheta coriaria may consume up to 154 sciarid eggs in 1 day.

When and where should you use it?

Atheta coriaria is suitable for use in covered crops at high Sciarid and shore fly densities, or at the beginning of an outbreak. It is suitable for use year round in all covered crops, including ornamentals, cucumber, strawberries and mushrooms. It is able to establish well in various growing media, including soil, peat, rock-wool and coir.

Atheta coriaria is less expensive than Hypoaspis miles mites, and the two may be combined to give improved Sciarid control.

How should you use it?

Rotate the tube horizontally to mix the contents before application.

Shake contents gently onto the potting media, algae and any other suspected Sciarid breeding grounds. A general application rate of 5 insects per square metre is recommended. Up to 10 insects per square metre should be used for infestation foci, particularly of shore flies. Atheta coriaria will quickly burrow into the media. Two releases at 7-day intervals may be made to encourage swifter establishment. Performance against Sciarid flies may be monitored with sticky traps, changed at weekly intervals. Pest catches will decline over 2-6 weeks. Reductions in shore flies are harder to judge using sticky traps because of the mobility of the adults. Flies from un-treated areas constantly re-invade treated areas, so that adult populations in treated and un-treated areas appear not to change, even when it is possible to demonstrate a 75% reduction in the number of adults emerging from treated trays of plants.

When should you not use it, and what are the alternatives?

Staphyline c should not be used preventatively unless there are sufficient alternative prey sources available. Atheta become cannibalistic at high densities or low food levels and are therefore not an efficient preventative agent.

Due to the high mobility of all Atheta coriaria life-stages, but especially the adults, this product is not recommended for use on outdoor crops.

Use with soil-administered insecticides is to be avoided. As a generalist predator, larvae of some soil-dwelling beneficials may also be attacked when prey is scarce and you should consult your distributor for advice of which species are complementary if using more than one. Hypoaspis, however, works independently of Atheta and both may be used for Sciarid control.

What will it do?

Atheta coriaria will control outbreaks of Sciarid flies and shore flies when used as directed. It should ideally be used when an outbreak is first indicated to control populations later in the season, or can also be used remedially once pest populations have become a problem.

What will it not do, and what are the control options?

Atheta coriaria will not attack adult shore flies or Sciarid flies, and should not be used where guaranteed elimination of the pest is required. A 90% reduction of Sciarids and 75% reduction in shore flies can be expected in 2-3 weeks, depending on initial prey density and release rate, so Atheta coriaria is unsuitable for crops where an immediate effect is required.

Although highly mobile, Atheta may not disperse to all sites of infestation until local food resources are exhausted. For this reason all Sciarid and shore fly breeding sites in the greenhouse should be treated.

Chemical compatibility

There is currently a lack of data on pesticide compatibility.