A native predatory rove beetle, Atheta coriaria, feeds on the eggs and larvae of both pests and recently became available as a biological control. However, Atheta beetles are expensive and have given variable results. Previously, in HDC project PC 239, knowledge on Atheta biology, rearing methods and potential as a biocontrol agent in integrated pest management programmes was reviewed and a simple, practical and inexpensive DIY method using turkey-rearing food was developed for growers to rear and release large numbers of Atheta.
PC 239a looked at a number of issues so that practical guidelines for rearing Atheta on the nursery might be possible. Commercially recommended release rates were found to be too low. In a trial with pot-grown parsley, good control of sciarid flies was achieved with a rate of Atheta equivalent to 500 per square metre, which would be too expensive if buying the beetles but possible if DIY-reared.
Within a week of placing rearing-release boxes of Atheta in a shore-fly-infested lettuce crop, the beetles had dispersed of their own accord and started breeding throughout a 2,000sq m glasshouse - so there would be no need to make direct releases.
The project has shown that growers could save money by on-nursery rearing of Atheta rove beetles for control of sciarid and shore flies. The HDC will be publishing a fact sheet shortly.