The papers presented in this special issue are focused on developing and validating procedures for artificial rearing of selected fruit fly species of economic importance for use in area-wide integrated pest programmes with a sterile insect technique (SIT) component. They are the result of a 5-year coordinated research project (CRP) on ‘Development and Improvement of Rearing Techniques for Anastrepha and Bactrocera Fruit Flies’ that was coordinated by the Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture. Twenty-two CRP participants from 18 countries worked on both basic and advanced rearing procedures of different fruit fly species to overcome technical bottlenecks and to develop appropriate and relevant procedures for use in mass-rearing facilities. A variety of studies were undertaken for three groups of tephritid species: (1) those for which mass-rearing for SIT application was available, but further refinement would be useful; (2) those for which mass-rearing for SIT application was under development in the laboratory, but that had not reached mass-rearing status; and (3) those for which research to develop colonization and rearing methods was needed. Many of the protocols developed or improved during the CRP have been transferred to the different fruit fly mass-rearing facilities worldwide.

The objective of this study was to determine whether a generic diet could be developed for three species of Anastrepha: A. ludens, A. obliqua and A.serpentina. Laboratory and mass-rearing tests to assess the suitability of the A. ludens (Loew) (ALU) diet, normally used for rearing A. ludens, indicated that it was also suitable for rearing A. obliqua (Macquart) and A. serpentina (Wiedemann). Therefore, this diet appeared to be a suitable generic diet for the three species based on quality control parameters. In comparison with those observed when rearing larvae on the commonly used A. obliqua diet, the number of A. obliqua larvae recovered per g diet increased from 4.2 to 5.1, larval weight increased from 17 to 18.2 mg, pupation after 24 h from 89.3 to 96.9%, adult emergence from 91.5 to 93.7% and flight ability (% of fliers) from 86.1 to 90.4% when reared on the ALU diet. Usually, A. serpentina larvae are reared on the A. serpentina diet, but when reared on the ALU diet, larval recovery increased from 61.8 to 69.8%, number of larvae recovered per g diet from 3.7 to 4.4, larval weight from 21.7 to 23.8 mg and flight ability from 64.6 to 70.2%. These results show that the nutritional requirements of the three Anastrepha species are similar. The use of a generic diet for rearing the three species requires only one line to prepare the diet, reducing time and labour costs.

In this study, the effects of relaxed mass-rearing conditions on Anastrepha obliqua (Macquart) production and quality were determined. Relaxed rearing conditions were defined by a reduction in the density of adult flies, from 80,000 to 60,000 flies per mass-rearing cage, and a reduction in the density of larvae, from 6.18 to 3.70 eggs/g of diet. In the parental generation, flies reared under relaxed conditions exhibited significant and a few non-significant changes – increased daily fecundity from 37 to 42 eggs per female, larval recovery from 80 to 91%, larval weight from 18.5 to 19.5 mg, pupation at 24 h from 92 to 96%, pupal weight from 13.5 to 14.3 mg, adult emergence from 92 to 94% and percentage of fliers from 89 to 90%. During the following 12 generations, non-significant differences were observed, but comparisons between relaxed and non-relaxed colonies were significant. The sexual competitiveness of males produced under relaxed conditions was similar to that of wild males.

In this study, laboratory and field cage experiments were conducted to assess the performance of sterile mass-reared Mexican fruit fly Anastrepha ludens (Loew) irradiated at various doses. In small laboratory cages, the radiation dose was found to have no effect on adult emergence, flying adults or survival at 25 days. In field cages, non-irradiated males and males irradiated at 20 and 40 Gy were found to exhibit greater mating propensity than males irradiated at 60 and 80 Gy. In large field cages in competition with wild males, cohorts of flies (male and female) irradiated at the low dose of 40 Gy and wild non-irradiated flies mated randomly, while flies irradiated at the high standard dose of 80 Gy mated assortatively. Irrespective of the radiation dose, laboratory flies courted and attempted copulation significantly earlier in the day than wild flies. In large field cages, cohorts of flies irradiated at low doses, e.g. 40 Gy, tended to induce greater sterility into a cohort of wild flies than those irradiated at 80 Gy, but the difference was not significant. Our results suggest that lowering the radiation dose currently applied to mass-reared flies in the Mexican fruit fly eradication campaign would substantially improve male mating performance. This could result in greater sterility induction without posing a risk in areas where target pest populations naturally prevail and are under suppression during the early stages of eradication programmes.

Outcrossing to wild or unrelated strains has been proposed as a counter to the negative effects of adaptation by domesticated animals to captive-breeding environments. However, for mass-reared insects intended for sterile insect technique release, outcrossing may reduce productivity in mass-rearing facilities. In this study, we characterized adaptation to mass-rearing in the Queensland fruit fly Bactrocera tryoni (Froggatt). The features of domesticated B. tryoni were similar to those of other domesticated tephritids: shortened preoviposition period, higher egg production and increased early survival. We also examined the practical use of outcrossing to improve mass-reared strains. The B. tryoni mass-reared strain was crossed with independent strains that had already been domesticated for a varying number of generations. Preoviposition period, egg production, survival and stress tolerance were measured in the resulting hybridized strains. The short preoviposition period of the mass-reared strain was retained in outcrossed flies, indicating a genetically dominant trait. Egg production in outcrossed flies exceeded the mid-parent value, indicating some hybrid vigour for this trait. If both parents exhibited high egg production, the egg production of outcrossed strains was as high as that of the mass-reared strain. The high early survival of domesticated tephritids was reduced in outcrossed females, but not in outcrossed males. Preliminary thermal stress tests revealed that outbred flies were more stress resistant than the mass-reared strain. Therefore, the anticipated loss of productivity in outcrossed B. tryoni mass-reared strains is avoidable by choosing suitable parental strains and the outcrossed flies should have improved field performance. Using already domesticated strains should also facilitate the annual renewal of hybrid strains.

In this study, new methods to improve the mass production of the Philippines fruit fly Bactrocera philippinensis Drew & Hancock were assessed. A new adult screen cage equipped with perforated egging tubes was designed. The replacement of sweet potato with sugarcane bagasse, rice straw or powdered corn as an alternative bulking agent in the standard artificial larval diet was found to lead to positive results in large-scale rearing. Rearing protocols and product quality control procedures for egg incubation, sieving of pupae and pupal holding were examined. The adoption of these new rearing procedures at low cost was found to increase the production of the Philippines fruit fly in a mass-rearing facility without reducing the fitness of the insect.

In this study, a liquid larval diet as an artificial rearing medium was successfully tested for the Philippines fruit fly Bactrocera philippinensis Drew & Hancock. The biological parameters studied were pupal weight, adult emergence and fliers, sex ratio, fecundity and fertility. The insects performed most satisfactorily if corn (maize) oil was added to the liquid medium. Compared with the standard sponge ‘Kalle’ cloth, three locally available absorbent materials showed promise as a support matrix for feeding larvae.

The application of the sterile insect technique to fruit flies involves the mass-production of the pest insects using an artificial diet, irradiation during a narrow time window at the late pupal or early imaginal stage to inhibit reproduction without affecting reproductive capacity, and then release into the target area where the sterile insects compete reproductively with their wild counterparts. The timing of irradiation is important to enable the release of males that are sterile but of good quality and exhibit an acceptable sexual performance. In this study, we examined the pupal development of 12 tephritid (Diptera: Tephritidae) species: Anastrepha fraterculus (Wiedemann), A. ludens (Loew), A. obliqua (Macquart), A. serpentina (Wiedemann), Bactrocera cucurbitae (Coquillett), B. dorsalis (Hendel), B. invadens (Drew, Tsuruta & White), B. oleae (Rossi), B. philippinensis (Drew & Hancock), B. tryoni (Froggatt), B. zonata (Saunders) and Ceratitis capitata (Wiedemann). The insects were reared at various temperatures, in the laboratory (15–28 °C) and under fluctuating natural conditions (20–35 °C). The gradual colour changes of the insect eyes during metamorphosis were observed and photographed, measuring the specific eye colour parameters of each species and matching them with the colour scale of the Munsell Soil Color Charts. The duration of pupal development and the time to emergence in Anastrepha species were longer than those in C. capitata and Bactrocera species at all the holding temperatures. The data obtained can be used by mass-rearing facilities to manage pupal holding conditions and as indicators for optimizing the timing of irradiation.

Fruit fly pests in north-eastern Brazil include several species of the genus Anastrepha and the Mediterranean fruit fly Ceratitis capitata (Wiedemann). The most common species are Anastrepha zenildae Zucchi, the South American fruit fly Anastrepha fraterculus (Wiedemann), the West Indian fruit fly Anastrepha obliqua (Macquart) and Anastrepha sororcula Zucchi. In this study, attempts were made to mass-rear A. zenildae and A. fraterculus. The objective was to adapt local populations to laboratory conditions and develop mass-rearing systems for further utilization in integrated area-wide control programmes. Small colonies initially fed on guava fruits were developed in the laboratory. Adults were fed a diet made of brown sugar (60%), hydrolysed corn protein (26%), brewer's yeast (5%) and honey (9%). Adult diets with other combinations of ingredients were also tested. The colonies of A. zenildae and A. fraterculus achieved mating and egg hatch rates of 32 and 39%, respectively. The best diets for adults, resulting in good egg hatch, were as follows: diet B – brown sugar (60%), hydrolysed corn protein (26%), brewer's yeast (5%) and honey (5%); diet C – hydrolysed corn protein and white sugar (1:3); and diet D – soybean protein and white sugar (1:3). The best larval diet was based on 18% sugarcane bagasse and 9% protein. Adult mortality during the first 15 days was still high, over 50%. Adult recovery from pupae was over 70%. The best oviposition substrate was an agar-coated glass bottle. Mating compatibility was highest for A. fraterculus from the state of São Paulo. Mating between A. fraterculus and A. zenildae yielded no viable eggs.

Mass-rearing protocols must be developed, in particular, a cost-effective larval diet, to implement the sterile insect technique against Anastrepha fraterculus (Wiedemann). The key elements of this diet are the optimal nutrients and their concentrations, diet supports or bulking agents, and the pH of the diet. To improve the currently used formulation and develop a more cost-effective diet, in the present study, we evaluated various supports, sugar contents, nutrient proportions and pH levels. Egg-to-pupa recovery was found to increase when agar was replaced with sponge cloth in the diet. Although low, the recovery values obtained when using the sugarcane bagasse-based diet were similar to those obtained when using the agar-based diet, but the percentage of adult emergence was lower. Larval viability was found to increase when the amount of sugar in the diet was doubled. Yet, it is still necessary to evaluate this diet on a larger scale and determine the feasibility of reusing the sponge cloth to reduce the costs of larval diets.

The South American fruit fly Anastrepha fraterculus (Wiedemann) is an important pest in many countries. The sterile insect technique is an effective method of controlling Ceratitis capitata (Wiedemann) in Argentina and has been proposed for use against A. fraterculus. Because this technique relies on sterile mass-reared males mating with wild females, it is essential to verify that artificial rearing does not reduce male mating competitiveness. Several morphometric characters were evaluated to detect differences between a wild population and a laboratory strain that was derived from it and reared artificially since 1997. Eight morphometric traits were analysed as indicators of body size, head shape and potential mobility: Thorax Length, Head Width, Face Width, Eye Length, Wing Length, Wing Width, Third Tibia Length and Femur Length. The results were analysed using multivariate analysis of variance, linear multiple regression and logistic multiple regression. In general, laboratory flies were larger than wild ones (possibly because the larval diet was supplied ad libitum). Laboratory males had significantly larger Head Width and Eye Length and a smaller Wing Width than wild males. Laboratory females differed from wild ones only by having narrower wings. These results could be due to environmental and genetic factors, or as a consequence of genetic drift (for the latter) during colony establishment plus gradual adaptation to laboratory conditions, where flight ability is most likely less important (resources are found easily at close distances). Also, short-distance interactions among individuals are more frequent in a colony, possibly favouring increased facial trait sizes by sexual selection. Because long-term morphological changes could represent the beginning of intraspecific differentiation, they should probably be worthy of some consideration if a large mass-rearing colony is established.

Bactrocera invadens Drew, Tsuruta & White and Ceratitis fasciventris (Bezzi) are the major fruit fly pests of fruits and vegetables in Africa. The effects of two types of larval diet, liquid and solid (carrot based), on various quality control parameters (pupal recovery, pupal weight, adult emergence, flight ability, fecundity and fertility) of the two fruit fly species were investigated for five generations. The potential to replace two imported ingredients (yeast and wheat germ oil) with inexpensive and locally available alternatives was also explored. Most of the quality control parameters evaluated (pupal recovery, pupal weight, adult emergence and fecundity) for B. invadens reared on a liquid diet outperformed those reared on the carrot-based solid diet. In contrast, even though C. fasciventris was able to develop successfully on the liquid diet, three of the quality control parameters evaluated (pupal recovery, pupal weight and fecundity) were significantly lower over the generations when compared with those from insects reared on a solid diet. Except for flight ability, the parameters of B. invadens reared on the diets subsituted with the local yeast were of lower quality compared with those reared on the liquid diet containing the imported yeast. Corn (maize) and soybean oils were promising substitutes for wheat germ oil in the liquid larval diet of B. invadens without compromising any of the quality control parameters.

Integration of the sterile insect technique (SIT) into the area-wide management of the peach fruit fly Bactrocera zonata (Saunders) is a promising alternative to the localized use of chemical control tactics. Implementation of the SIT requires adequate numbers of sterile male insects that are produced in large mass-rearing facilities. The present study was carried out to improve the rearing methods of the peach fruit fly so as to contribute to the development of effective mass-rearing protocols. Commercially available papaya, mango, peach and guava juices were found to be equally effective as oviposition stimulants. Moreover, with respect to the fecundity and fertility of flies, water was found to be as effective as the tested fruit juices. During the first 3 weeks, 90% of the total eggs produced were collected from adult oviposition cages holding 50,000 flies. A larval diet composed of sugarcane bagasse, ground maize, sugarcane sugar, waste brewer's yeast, wheat bran, benzoic acid, nipagin and water resulted in the following values for the quality control parameters: egg hatch 85%, pupal recovery >67%, pupal weight >4.2 g, pupation >95%, adult emergence >89%, and fliers >65%. Adult emergence and flight ability were similar for pupae placed in sand and vermiculite as the pupation medium.

The effectiveness of rearing fruit flies (Diptera: Tephritidae) for parasitoid production and pest control need to be improved. In these studies, the effects of dietary protein ingredients on the biological parameters of the peach fruit fly Bactrocerazonata (Saunders) for parasitoid production were investigated. Among the various food ingredients, torula yeast and brewer's yeast were found to be more promising than Nu-Lure® and protein hydrolysate for rearing of B. zonata. To reduce the infestation of this pest in mango Mangifera indica L. orchards, biological control agents and the male annihilation technique were evaluated. Significantly fewer fruits were infested with fruit flies in the treated blocks compared with fruits in the untreated block. The field efficacy of the hymenopteran larval and pupal parasitoids Aganaspis (Trybliographa) daci (Weld) and Dirhinus giffardii Silvestri, respectively, plus the male annihilation technique in controlling fruit flies was significantly high than that of biological control agents and male annihilation as separate treatments. The release of parasitoids as agents of biological control can play a major role in the suppression of fruit fly populations and parasitoids also pose a minimal non-target risk. Furthermore, combining control tactics could be a very important aspect of an action plan for fruit fly population suppression.

Research on the olive fruit fly Bactrocera oleae (Rossi) – rearing simplification, insect microflora and transgenic strain evaluation – yielded several findings: (1) incorporation of antibiotics in the adult diet is evidently not needed; (2) colonization appears to be easier when wild adults are collected from the field instead of using mature larvae emerging from field-collected infested olives; (3) a combination of standard solid starter with liquid (no cellulose powder) finisher impregnated in synthetic sponge larval diets was more promising compared with all-liquid diets; (4) molecular analysis revealed extensive differences in bacterial species associated with the fly between laboratory flies and strains from different olive varieties, as well as between strains originating from different seasons of the year; (5) when an enhanced green fluorescent protein transgenic strain was compared with the standard long mass-reared strain, it proved significantly inferior according to all quality control tests applied, i.e. egg production, egg hatch, larval-stage duration, pupal recovery, pupal weight, adult emergence and adult survival. The aforementioned findings are discussed in the context of mass rearing and quality requirements for more successful implementation of the sterile insect technique against this pest.

Mutualistic bacterial endosymbionts provide many benefits to their insect hosts, but their role in mating has not been studied in the past. In this study, we examined copulatory success and mating latency as two parameters of mating success to assess the influence of Candidatus Erwinia dacicola on mating between a laboratory population of olive flies (Bactrocera oleae Rossi) of Israel origin and a wild population of olive flies from Israel. Previous studies have shown that in many species of tephritid flies, laboratory-reared males have lower fitness and achieve fewer matings than wild males. Our research has shown that this Israeli population of olive flies reared in the laboratory on an artificial diet lacked an endosymbiont, Ca. E. dacicola, found in wild-caught insects from Israel. We hypothesized that decreased fitness and mating ability in laboratory-reared flies could be due to the absence of this endosymbiont. Mating assays between both sexes of these two Israeli populations revealed matings to occur primarily between laboratory-reared females and wild males. Laboratory-reared males achieved only 22% of the total matings. Candidatus Erwinia dacicola was found in significantly fewer insects from the laboratory population than in the wild population; within populations, male and female olive flies were equally likely to have the endosymbiont. However, differences in readiness to mate between the two populations, and not the presence of the endosymbiont, explained mating latency.

In this study, rearing systems for, and the quality and demographic parameters of, a wild strain (WS) and two laboratory strains (LSs; one maintained on a torula yeast-casein diet and the other on a starter-gel diet) were determined for the American guava fruit fly Anastrepha striata (Schiner). No differences were observed between the LSs, but there were significant differences between the LSs and WSs. The LSs had the highest values for larval recovery, pupal weight, egg hatch, number of eggs/female per day, net reproductive rate and intrinsic rate of increase. Therefore, during a short oviposition period, the LSs had a high fecundity. There were no differences in pupation at 24 h and larval weight between the WS and LS. However, the values of parameters, adult emergence, female and male life expectancies, age at first oviposition, oviposition and post-oviposition periods and mean generation time were the highest in the WS.

In this study, the effects of yeast protein hydrolysate (YPH): sucrose proportions in the adult diet of the Ethiopian fruit fly Dacus ciliatus Loew on survival, pupal production, and endogenous lipid and protein contents were investigated. Small populations of the fly were fed diets containing various proportions of YPH and sucrose under low-humidity and high-humidity conditions. The YPH: sucrose proportions ranged from 20 to 50%. We monitored the patterns of survival, pupal production, and individual endogenous protein and lipid loads (only under high-humidity conditions) in flies maintained on various adult diets. The survival patterns of both males and females under high-humidity conditions were inversely proportional to the proportion of YPH in the diet. Mortality of some adult flies was related to the stickiness of the highly hygroscopic adult food mix. By contrast, the survival patterns of males and females maintained under low-humidity conditions were directly proportional to the proportion of YPH in the diet. Apparently, there was no effect of diet type on the number of pupae produced; on the sucrose-only diet, flies produced significantly fewer pupae. Protein content in the flies increased significantly as the proportion of protein in the diet increased, but lipid content was clearly not related to food constitution. Based on these results and recent evidence from studies in other fruit fly species, we concluded that a large amount of protein is deleterious to the fruit flies. Workers in rearing facilities should investigate and tailor different food-delivery systems, e.g. separate dishes for carbohydrates and the food mix, and reduce the amount of YPH used in industrial adult diets.

In this study, the basic biology of and artificial rearing techniques for Bactrocera pyrifoliae (Drew and Hancock), a pest of peaches and plums in high-elevation areas of northern Vietnam and Thailand, were investigated for 5 years. Bactrocera pyrifoliae was found only between elevations of 1000 and 1500 m, heavily infesting peaches and plums from early June to harvest in mid-July. The durations of the egg, larval and pupal stages were determined under controlled environmental conditions in the laboratory, indicating that B. pyrifoliae is a multivoltine species. Larvae were successfully reared on a carrot and corn powder-based diet. Determinations of the appropriate adult density in colony cages, and also optimal temperature conditions for holding adults, were made. Bactrocera pyrifoliae performed better when the temperature was lowered during the night, as would be expected for a species adapted to temperate-like environments. Interestingly, adults originating from field-collected pupae emerged with a 3:1 female-biased sex ratio. Laboratory colonies, by generation seven, appeared to exhibit signs of inbreeding depression and required periodic incorporation of wild insects to restore egg hatch. To develop sound management techniques for populations of B. pyrifoliae infesting peaches, alternate commercial and native hosts infested outside the peach and plum fruiting season must be identified or some form of overwintering mechanism such as reproductive diapause be discovered. Documentation of mating behaviour in the field (a key to developing efficient traps), improvement in fertility in laboratory colonies, and eventually sterile insect technique-based integrated pest management for pest population management in the expanding low-chill temperate fruit-growing areas of northern Vietnam are also needed.