Development of a Pupal Color-Based Genetic Sexing Strain of the Melon Fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae)

The Þrst genetic sexing system for the melon ßy, Bactrocera cucurbitae (Coquillett), based on pupal color was developed. The recessive white pupae mutant, wh, was used in a putative chromosome translocation linking the wildtype allele to the male sex. This system permits the separation of males (wildtype brown pupae) from females (mutant white pupae). Results from laboratory studies indicated that egghatch averaged 42% for ßies 2Ð5wkold,withhigher rates ( 50%) for younger ßies in this age range. Male larvae left the diet to pupate earlier than females, averaging 60% of the pupae in the Þrst day of collection, whereas only 40% on the fourth day of collection. Adult emergence ratewasnormal, averaging 92%.Adult egg fecundity and fertility (both sexes)were very low ( 1% of normal) after irradiation at 100 Gy at 1, 2, or 3 d before emergence. Adult ßight ability from standard 20-cm tubes averaged 65%. Irradiated females landed on, and oviposited into, zucchini fruit signiÞcantly fewer times than nonirradiated females. Field cage survival tests indicated that the new strain survived as well ( 80%) as wild males over a 7-d period when provided with food and water. Mating tests indicated that male-only sterile ßies mated signiÞcantly more (about double) with wild females than sterile males from bisexual (male and female) sterile populations competing withwildmales.Males fedonly sugar until tested in the cages failed tomatewithwild females,whereas males fed a low protein diet (6:1 sugar:protein) or the standard 3:1 diet mated as well as wild males for wild females. Finally, males exposed to the attractant, cuelure, failed to improve their mating performance compared with control, unexposedmales. The results are discussed in the context of the potential for using the new strain in current or future melon ßy sterile insect technique programs in Hawaii and elsewhere.