In this section:
Biological Control Agent
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Fly first released on Yorke Peninsula, South Australia, in summer 2000
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The larval stage of the fly feeds on the snail
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The fly is active over summer when snails are aestivating (resting).
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Main target of the fly is the conical snail Cochlicella acuta
The parasitic fly Sarcophaga penicillata (Villeneuve), was identified as a promising candidate for the biological control of C.acuta and was imported from southern Europe for assessment in the mid 1990's. Following a lengthy quarantine testing period, S. penicillata was cleared for release in Australia 2000.
Lifecycle of the parasitic fly Sarcophaga penicillata
During summer adult S. penicillata flies mate and the female fly places a single larva in the opening of the snail shell. The larva feeds on the flesh of the resting snail, killing it. The larva pupates inside the snail and after about 18 days emerges as an adult fly. The emerged adult flies mate and the reproductive cycle starts again. Several generations are possible over summer.
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Fly larva (0.6mm) |
Fly pupa inside snail |
Emerging Fly from snail |
During the winter months, the pupal stage remains within the snail shell for up to six months, emerging as an adult fly at the start of summer.
Culture rearing
Flies are reared within insectary rooms especially designed for rearing insect cultures in SARDI, Entomology. Each room is controlled for light and temperature; set at 26oC with a 12 hour light: 12 hour dark photoperiod set to simulate optimum conditions for fly breeding. During the warmer months of the year, flies are mass-reared and are released at various field sites on Yorke Peninsula, South Australia. The two photos below show some of the mass rearing set-ups currently used at SARDI.
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Small cages for rearing flies |
Large cages for mass rearing |
Fly release
Research in to the release and establishment of the fly is ongoing by SARDI Entomology Staff. Sarcophaga penicillata has been released at 20 sites on Yorke Peninsula since April 2000. Recoveries of parasites indicate fly establishment has occurred in at least five sites at the time of publication. The highest level of parasitism recorded in the field to date is 10% and the greatest rate of spread recorded from a release point is 1km over a two-year period.
Fly releases occur in Spring, Summer and Autumn at field sites with a high number of adult conical snails and a total snail population of over 200 snails/ m2. Ideal release sites for the fly are undisturbed revegetation areas near a crop. At each site over 200 flies are released inside a mesh tent. To help ensure maximum survival of the first generation flies, the flies have access to honey, squashed snails and water inside the tent. The tent remains at the site for several weeks before being removed. The flies emerging from conical snails are able to disperse from the release point. After the release, a sample of snails is taken from the site and taken back to the laboratory to check for fly emergence. Levels of fly parasitism and establishment are recorded for each release site.
Monitoring of fly dispersal and establishment will continue during 2003-2004 and 2004-2005 summers.
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Releases occur over the summer months when the fly is active. |
Nursery Sites
During the summers of 2002/2003 and 2003/2004 we established three Nursery Sites on Yorke Peninsula where large numbers of flies were released. It is hoped that the fly will establish at these sites and disperse.
