Ginger root oil increases mating competitiveness of sterile Mediterranean fruit fly (Diptera:Tephritidae) in Western Australia

The exposure of sterile male Mediterranean fruit fly, Ceratitis capitata (Wiedemann) to the aroma of essential oil derived from ginger root Zingiber officinale Roscoe (GRO) has been shown in field cage trials to increase their mating success. This field cage study compared the mating performance of mass reared sterile Mediterranean fruit fly males prepared for ground release programmes under four different post-irradiation systems, two of which involved exposure of the flies to GRO aroma. In the first system, irradiated pupae were placed into non-vented 5-L paper tubs, individually aromatized by 20l of GRO (4ml/m3) for 96-120h until the adults were 2-3days old. In the second system, irradiated pupae were placed in vented 5-L paper tubs, exposed for 24h in a GRO aromatized room (0.5ml/m3) when the adults were 3days old and contained until required for mating tests at 5days old. The third and fourth systems were the same as the first two systems respectively, except that the flies were not exposed to GRO aroma. Significant differences in mating success were found among treatments. The exposure of 2 to 3-day old flies to GRO aroma improved mating performance slightly compared with equivalent non-exposed flies, but it was still below the minimum value accepted under international standards, while 27% of unexposed 5-day-old sterile males mated and had competitiveness (Fried value 0.38) slightly above this minimum level. GRO exposed 5-day-old flies had the highest mating percentage (67%) and a level of competitiveness (Fried value 1.81) based on induced sterility above that of wild flies (Fried value 1). The results indicate that the effectiveness of sterile male ground release programmes can be increased significantly by releasing 5-day-old sterile males that have been exposed to GRO in an entirely aromatized adult fly holding room.