A preliminary evaluation of a sheep blowfly trap in the Western Cape.

An insecticide-free sheep blowfly trapping system, utilising a synthetic lure, was evaluated at 4 localities in the Western Cape. Control sites, where no suppression was practised, were identified for each locality. The blowfly population was monitored for 48 hours monthly at each of the localities. Five to 7 suppression traps at the respective localities were identified for this purpose. Three to 10 traps were set monthly for monitoring in the control areas. Trapping resulted in the suppression (P < 0.01) of the Lucilia population at Caledon, where a large area of approximately 50 km2 was trapped. The suppression area of all the localities was < or =850 ha. At Elsenburg, blowfly numbers were low. There was a strong suggestion of a general reduction in the Lucilia numbers at this locality. Trapping failed to reduce Lucilia numbers at Tygerhoek and Langgewens. Lack of control over the influx of Lucilia from adjacent sheep-producing areas probably contributed to this result. The observed response at Elsenburg was probably due to its situation in a predominantly wine-growing area. Most of the blowflies recovered from the control traps during the month with the highest yield at the respective localities belonged to the genus Lucilia. The results obtained at Caledon and published reports suggest that large-scale trapping of Lucilia spp. may play a role in an integrated pest management system for blowflies.