Improving post-factory performance of sterile male fruit flies in support of the sterile insect technique

The sterile insect technique (SIT) is being applied against tephritid fruit fly pests in many areas of the world. Currently, fruit fly factories have the capacity to produce and sterilize several billion (thousand million) sterile insects per week, and to make them available for shipment to their final destinations. At sterile fly emergence and release facilities, the emerging flies are fed and held close to maturity, and then collected for area-wide release. While much research effort has been invested in improving mass-rearing and quality-control procedures at the fly-factory level, the post-factory handling of sterile flies has received much less attention. However, research (conducted mainly from 2000 onwards) has focussed on developing and validating ways of improving sterile male performance through better management during a critical period (starting with the arrival of pupae at the fly emergence and release facility and ending with the release of the sterile flies in the field). This chapter summarizes the progress made on this subject for fruit fly species (in the genera Anastrepha, Bactrocera, Ceratitis and Zeugodacus) against which the SIT is being applied. To increase the effectiveness of fruit fly SIT programmes, exposure of sterile males to nutritional, hormonal, and semiochemical treatments has been assessed for improvement in sterile male performance, and enhancement of post-factory handling and release methods. Incorporation of protein and juvenile hormone into pre-release Anastrepha spp. diets significantly accelerates sterile male maturation and improves sexual performance in several species. Improved or probiotic adult diets and semiochemical treatments using ginger root oil or citrus oils in Ceratitis capitata, and methyl eugenol and raspberry ketone in Bactrocera and Zeugodacus species, significantly increase sterile male mating competitiveness. Some of these treatments and improvements have been transferred to, and are being applied routinely in, operational programmes. However, these efforts need to be further strengthened to assess the interaction among different environmental and holding conditions, treatments and release systems, and to improve further the performance of mass-produced sterile males, a critical component of increasing the effectiveness of operational programmes.