MASS REARING OF ANASTREPHA FRATERCULUS (DIPTERA: TEPHRITIDAE): A PRELIMINARY STRATEGY

The South American fruit fly, Anastrepha fraterculus (Wiedemann), occurs from Mexico to Argentina and attacks some 80 species of host plants, including mango, citrus, guava, apple and coffee (Da Silva et al. 1996). In extensive fruit producing regions of Uruguay, Argentina and Peru, the only two fruit fly species of economic and quarantine importance areA. fraterculus and the introduced Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Manso & Lifchitz 1992). Unfortunately, there is as yet no environmentally friendly and effective strategy as Sterile Insect Technique (SIT) to use against A. fraterculus. If no reliable and economic methods were found, any possible benefits from C. capitata control in areas where it is sympatric with A. fraterculus, would be greatly reduced. The ability to massrear A. fraterculus is the key to development of SIT. At the A. fraterculus mass rearing Workshop held in 1996 at Vinia del Mar, Chile, various participants from Argentina, Brazil, Colombia and Peru reported on their efforts to rear this fruit fly under laboratory conditions (Ortiz 1999). It was agreed that the main limiting factor to successful mass rearing was the need to develop a technique that would promote effective oviposition, facilitate collection of the eggs, and assure maximum fertility of the eggs (Salles 1992, 1999) Here we describe a new method to potentially mass-rear A. fraterculus that produces high egg fertility and allows eggs to be collected easily with a minimum handling. REARING ROOM: Rearing conditions were 23 ? 2?C and 60-80% R.H., light intensity ranged from 4,000 to 5,000 lx, with a photoperiod of 12:12 (L:D). CAGES: The colony was kept in iron-framed cages (0.96 x 0.60 x 0.30 m), with a front and rear panel. The rear panel was covered with a fabric (voile) with 25 holes per linear centimeter. The front panel was made of the same fabric coated with a thin layer of transparent silicon rubber (0.5 mm thickness). This panel is very similar to that used for A. obliqua in Mexico (Dominguez, 1998). One or 2 days before emergence, 8,500 pupae were placed in each cage. After 10-14 days adults mated and begun oviposition. Adults were kept in the cages for 40 days. EGG COLLECTION: Females laid their eggs through the oviposition panels onto foam rubber sheets (0.01 x 0.90 x 0.60 m), which were moistened with a mixture of water and peach juice (3:1) to avoid the dehydration and to attract females to oviposit. After 24 h the foam rubber sheets were taken out and washed in water to collect the eggs. The eggs were placed in a wet chamber (petri dishes with wet filter paper in the bottom) and kept at a temperature of 23-260C until hatching. After 48 h the eggs began to hatch. LARVAL DEVELOPMENT: The diet described by Salles (1992) was used with the addition of streptomycin sulfate at rates of 1 g per thousand to avoid bacterial contamination. Two hundred grams of diet was poured over the trays (18 x 12 cm) 2 cm deep. After 48 h the eggs were placed on the larval diet at a density of 8 to 10 eggs per gram of diet. The trays were placed in racks and covered with a fine voile mesh to prevent contamination by Drosophila spp. Wet sand was incorporated in the bottom of the racks. The larvae developed in the diet and, 16 days later, they crawled out of the trays and buried in the sand to pupate. PUPATION: The pupae were collected and maintained, in a small container with sterilized wet sand. Fifteen days later they were introduced in cages to begin a new cycle. ADULTS: Adults were maintained on a mixture of yeast hydrolyzed enzymatic 10 g; corn protein 10 g; sugar 40 g; water 50 ml; vitamins (Dayamineral, Abbott) 500 mg; aminoacids (Aminocefa 5%, Roux Ocefa) 1 ml. Water was also supplied to the adults. This rearing has been carried out over 18 generation (F18) without problems. QUALITY CONTROL: The quality of insects was assessed using some of standard quality control based in IAEA, USDA, FAO Quality Control publication (IAEA, USDA, FAO. 1998) and Orozco et al. (1983). REARING PARAMETERS: Results of tests mentioned above are shown in Table 1.The main differences between our rearing technique and 3 previously published methods are shown in Table 2. The four rearing techniques used different oviposition devices. Nuniez & Guzman (1999) and Salles (1992, 1999) used colored hemispheres or domes to attract the female fruit flies and to stimulate oviposition, but they had to be placed inside the cage, which made handling difficult. Using