The effects of geographic origin and antibiotic treatment on the gut symbiotic communities of Bactrocera oleae populations

The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is the major insect pest of olive orchards (Olea europaea L.), causing extensive damages on cultivated olive crops worldwide. Due to its economic importance, it has been the target species for a variety of population control approaches including the sterile insect technique (SIT). However, the inefficiency of the current mass‐rearing techniques impedes the successful application of area‐wide integrated pest management programs with an SIT component. It has been shown that insect mass rearing and quality of sterile insects can be improved by the manipulation of the insect gut microbiota and probiotic applications. In order to exploit the gut bacteria, it is important to investigate the structure of the gut microbial community. In the current study, we characterized the gut bacterial profile of two wild olive fruit fly populations introduced in laboratory conditions using next generation sequencing of two regions of the 16S rRNA gene. We compared the microbiota profiles regarding the geographic origin of the samples. Additionally, we investigated potential changes in the gut bacteria community before and after the first exposure of the wild adult flies to artificial adult diet with and without antibiotics. Various genera – such as Erwinia, Providencia, Enterobacter, and Klebsiella – were detected for the first time in B. oleae. The most dominant species was Candidatus Erwinia dacicola Capuzzo et al. and it was not affected by the antibiotics in the artificial adult diet used in the first generation of laboratory rearing. Geographic origin affected the overall structure of the gut community of the olive fruit fly, but antibiotic treatment in the first generation did not significantly alter the gut microbiota community.     

Methoprene application and diet protein supplementation to male melon fly,Bactrocera cucurbitae,modifies female remating behavior

Methoprene (an analogue of juvenile hormone) application and feeding on a protein diet is known to enhance male melon fly, Bactrocera cucurbitae Coquillett (Diptera: Tephritidae), mating success. In this study, we investigated the effect of these treatments on male B. cucurbitae's ability to inhibit female remating. While 14‐d‐old females were fed on protein diet, 6‐d‐old males were exposed to one of the following treatments: (i) topical application of methoprene and fed on a protein diet; (ii) no methoprene but fed on a protein diet; (iii) methoprene and sugar‐fed only; and (iv) sugar‐fed, 14‐d‐old males acted as controls. Treatments had no effect on a male's ability to depress the female remating receptivity in comparison to the control. Females mated with protein‐deprived males showed higher remating receptivity than females first mated with protein‐fed males. Methoprene and protein diet interaction had a positive effect on male mating success during the first and second mating of females. Significantly more females first mated with sugar‐fed males remated with protein‐fed males and females first mated with methoprene treated and protein‐fed males were more likely to remate with similarly treated males. Females mating latency (time to start mating) was significantly shorter with protein‐fed males, and mating duration was significantly longer with protein‐fed males compared with protein‐deprived males. These results are discussed in the context of methoprene and/or dietary protein as prerelease treatment of sterile males in area‐wide control of melon fly integrating the sterile insect technique (SIT).     

Oviposition response and development of the egg-pupal parasitoid Fopius arisanus on Bactrocera oleae, a tephritid fruit fly pest of olive in the Mediterranean basin

To date, information is wanting with regard to the use of new exotic parasitoids against olive fruit fly, Bactrocera (=Dacus) oleae (Gmelin) (Diptera: Tephritidae), a serious pest of olives Olea europaea L., in the Mediterranean basin. We investigated the oviposition response and developmental biology on B. oleae of Fopius (=Biosteres) arisanus (Sonan) (=Opius oophilus Fullaway) (Hymenoptera: Braconidae), an egg-pupal parasitoid of tephritid fruit flies, never tested before as a potential parasitoid of this host. Our results showed that olive fruits infested with B. oleae eggs exerted a relevant attraction to gravid F. arisanus and represented a stimulus for oviposition. Nevertheless they were not as attractive to female parasitoids as the Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae), eggs infested papaya fruits (Carica papaya L.). In our experimental conditions, F. arisanus completed development in B. oleae within 33 ± 1.7 days (males) and 35 ± 1.6 (females). Increases in host egg to female parasitoid ratios of 1:1, 5:1, 10:1 and 20:1 corresponded with decreases in the percentage of B. oleae parasitisation and host killing but corresponded also with increases in absolute parasitisation. Our findings are discussed in light of possibilities of utilising F. arisanus for biological control of olive fruit fly.     

Evaluation of yeasts in gel larval diet for Queensland fruit fly,Bactrocera tryoni

Queensland fruit fly, Bactrocera tryoni (“Q‐fly”), is Australia’s most economically important insect pest of horticultural and commercial crops especially in the eastern regions. The sterile insect technique (SIT) has been adopted as an environmentally benign and sustainable approach for management of Q‐fly outbreaks. High‐performance larval diets are required to produce the millions of flies needed each week for SIT. Yeast products contribute amino acids (protein) to fruit fly larval diets, as well as carbohydrate, fat and micronutrients, but there can be substantial variation in the nutritional composition and suitability of yeast products for use in larval diets. Gel larval diets have recently been developed for large‐scale rearing of Q‐fly for SIT, and composition of these diets requires optimization for both performance and cost, including choice of yeast products. We assessed performance of Q‐flies reared on gel larval diets that contained debittered brewer’s yeast (Lallemand LBI2240), hydrolysed yeast (Lallemand FNILS65), inactivated brewer’s yeast (Lallemand LBI2250) and inactivated torula yeast (Lallemand 2160‐50), including blends. Q‐flies performed poorly when reared on diets containing only or mostly hydrolysed yeast in terms of pupal number, pupal weight and percentage of fliers. Performance was also poor on diets containing high proportions of torula yeast. Overall, debittered brewer’s yeast is recommended as the best option for Q‐fly gel larval diet, as it is cheap, readily available, and produces flies with good performance in quality control assays. Inactivated brewer’s yeast produced flies of comparable quality with only a modest increase in cost and would also serve as an effective alternative.     

Bacterially enriched diet improves sexual performance of sterile male Mediterranean fruit flies

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), (medfly) is a polyphagous and cosmopolitan agricultural pest, targeted in many areas for control by the Sterile Insect Technique (SIT). Our objective in the present study was to test the hypothesis that a bacterially enriched diet provided to sterile males will improve their sexual performance in competitive settings that emulate natural conditions. Specifically we determined how feeding on diets enriched with Klebsiella oxytoca affected the ability of sterile males to compete for wild females against wild males, their ability to inhibit female receptivity, and their survival. We found that enriching the sterile male diet with K.oxytoca significantly improved mating competitiveness in the laboratory and in field cages. In addition, bacterially enriched sterile males inhibited female receptivity more efficiently than sugar fed males and survived longer duration of starvation. We conclude that inoculating mass reared sterile flies with bacteria prior to their release is a valid approach to improve the efficacy of SIT.     

Effect of heat stress on survival and reproduction of the olive fruit fly Bactocera (Dacus) oleae

The olive fruit fly Bactrocera (Dacus) oleae Gmelin is a major olive pest in Greece and other Mediterranean countries. Its population density and respective olive infestation is usually low in many areas of northern Greece during summer months. To some extent, this may be due to the prevailing high temperature and low relative humidity conditions. In the present work the effects of short term exposure to high temperatures on the survival and egg production of B. oleae pre‐imaginal stages and adults were studied under laboratory conditions. Different larval instars within infested green olive fruits, adults and pupae and were exposed for 2 h to a series of different high constant temperatures ranging from 34 to 42°C. Subsequently, survival percentages of pre‐imaginal stages and adults as well as the number of eggs laid by females previously exposed to high temperatures were determined. At temperatures up to 38°C high survival percentages of larvae and adults were observed, whereas pupae displayed a relatively increased heat tolerance up to 40°C. Female longevity and egg production were substantially reduced after heat stress. Prior acclimation at 33°C for 1 and 3 days resulted in increased adult survival following heat stress. We discuss the results with respect to the ability of the fly to survive and reproduce under high summer temperatures.     

Prospects for improving biological control of olive fruit fly,Bactrocera oleae (Diptera: Tephritidae), with introduced parasitoids (Hymenoptera)

Olive fruit fly is a key pest of olive and consequently a serious threat to olive fruit and oil production throughout the Mediterranean region. With the establishment of Bactrocera oleae in California a decade ago, interest was renewed in classical (introduction) biological control of the pest. Here we discuss the prospects of identifying natural enemies of B. oleae in Africa and Asia that may help reduce B. oleae populations in California and elsewhere. Based on the current understanding of Bactrocera phylogenetics, early opinions that B. oleae originated in Africa or western Asia rather than the Mediterranean region or the Near East are taxonomically and ecologically supportable. Closely related to cultivated olive, the wild olive Olea europaea cuspidata is widely distributed in southern and eastern Africa, the Arabian Peninsula, and eastwards into Asia as far as southwestern China. Little is known regarding the biology and ecology of B. oleae in Africa and eastern Asia, especially in wild olives. While the diversity of parasitoids of B. oleae in the Mediterranean region is low and unspecialized, a diverse assemblage of parasitoids is known from B. oleae in Africa. Conversely, regions in Asia have remained largely unexplored for B. oleae and its natural enemies.     

The biology of Bracon celer as a parasitoid of the olive fruit fly

A series of laboratory experiments was conducted on a colony of Bracon celer Szépligeti (Hymenoptera: Braconidae) reared on the olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae). Female B. celer preferentially probe and oviposit into olives containing late third-instar fly larvae. The parasitoid develops as a solitary, ectoparasitic idiobiont. Mean development time (oviposition to adult eclosion) at 22 °C was, for females, 36±1 (SE) days, and for males, 34±1 days. The mean longevity of adult female wasps when provided honey and water was significantly greater than when they were provided water alone, or nothing. The females produced an average of 9.7±7.2 progeny during their lifetimes, but production levels in the insectary colony suggested that this level of fecundity was artificially low and could be improved. The discrepancy may be a consequence of constraints on oviposition behavior imposed by the experimental design. The results are discussed with respect to insectary production methods and the potential use of B. celer as a biological control agent for olive fly in California.     

Field evaluation of the susceptibility of mill and table olive varieties to egg‐laying of olive fly

The susceptibility of 20 widely distributed mill and table olive varieties to Bactrocera oleae (Rossi) as affected by irrigation, and fruit diameter and oil content was evaluated in a 3‐year trial in Southern Spain. Bactrocera oleae was bivoltine life cycle in the experimental site, with significant differences among population size throughout the study. Even though the olive fruit fly damaged all varieties, significant differences in susceptibility were detected. Among the mill olive varieties “Nevadillo Blanco de Jaén” was the most susceptible, with average infestation levels ranging between 6.7% and 52.2% and between 10.3% and 69.2% under rainfed and irrigated conditions, respectively, and “Arbequina” was the least susceptible, with average infestation levels ranging between 0.6% and 12.7% and between 2.3% and 18.5% under rainfed and irrigated conditions, respectively. Among the table olive varieties, “Gordal Sevillana,” “Ascolana Tenera” and “Ocal” were the most susceptible (with average infestation levels reaching 39.7%, 36.5% and 33.3%, respectively), while “Callosina” was the least susceptible (with infestation levels of only 8.4%). Irrigation tended to promote both B. oleae infestation and its earlier occurrence compared to the rainfed condition. Even though the diameter and oil content were positively correlated with B. oleae fruit infestation (correlation coefficients ranged between 0.5 and 0.95), the present work reveals that other yet‐unknown factors may influence B. oleae oviposition preferences. The results of this study can be useful for breeding programmes to develop olive varieties resistant to B. oleae and provide key information for wide‐area olive fly pest management decisions.     

Lifespan and patterns of accumulation and mobilization of nutrients in the sugar-fed phorid fly, Pseudacteon tricuspis

Abstract. The effect of sugar feeding on the survival of adult phorid fly Pseudacteon tricuspis is investigated. Flies fed 25% sucrose in aqueous solution continuously throughout their lifespan have greater longevity (mean ± SE longevity: female = 7.9 ± 0.8 days, male = 8.9 ± 0.9 days) than completely starved (provided no water and no sugar solution) flies, sugar-starved (provided water only) flies, or flies fed sugar solution only on their first day of adult life. Completely starved flies rarely lived beyond one day. Provision of water increases longevity by 2 days, and one full day of sugar feeding further increases longevity by an additional 1–2 days. Flies fed 50% sucrose have similar survivorship as those fed 25% sucrose. The temporal patterns of nutrient accumulation and utilization are also compared in P. tricuspis fed different diets: sugar-starved, sucrose-fed on the first day of adult life only, and sucrose-fed continuously. Adult P. tricuspis emerge with no gut sugars, and only minimal amounts of body sugars and glycogen. Although the levels of body sugars and glycogen decline gradually in sugar-starved flies, a single day of sugar feeding results in the accumulation of maximum amounts of gut sugars, body sugars and glycogen. High levels of these nutrients are maintained in female and male phorid flies fed on sucrose continuously over the observation period, whereas nutrient levels decline in flies fed only on the first day of life, beginning 1 day postfeeding. Female and male P. tricuspis emerge with an estimated 12.3 ± 2.3 and 7.2 ± 1 g of lipid reserves per fly, respectively. These teneral amounts represent the highest lipid levels detected in adult flies, irrespective of their diet, and are maintained over the life times of sucrose-fed female and male flies, but declined steadily in sugar-starved females. These data suggest that adult P. tricuspis are capable of converting dietary sucrose to body sugars and glycogen, but not lipids.     

Genome size estimation with quantitative real‐time PCR in two Tephritidae species: Ceratitis capitata and Bactrocera oleae

The medfly Ceratitis capitata and the olive fruit fly Bactrocera oleae belong to the Tephritidae family of Diptera, a family whose members cause severe damages in agriculture worldwide. For such insect pests, the utmost concern is their population control. The sterile insect technique (SIT) has been used in the Tephritidae family with varying degrees of success. Its efficient use usually depends on the development of genetic sexing strains and the release of only male flies. However, such advances are based on modern genetic, molecular and genomic tools. The medfly is clearly the prototype of the family, since such tools have advanced considerably, which has resulted in effective SIT efforts around the world. A whole‐genome sequencing project of this insect is already underway. In contrast, similar tools in the olive fly lag behind, even though the insect is considered a promising candidate for a next SIT target. An accurate estimate of genome size provides a preliminary view of genome complexity and indicates possible difficulties in genome assembly in whole‐genome projects. Taking advantage of a quantitative real‐time PCR approach, we determined the genome size of these two species C. capitata and B. oleae as 591 Mb (CI range: 577–605 Mb) and 322 Mb (CI range: 310–334 Mb) respectively.     

Transinfection of the olive fruit fly Bactrocera oleae with Wolbachia: towards a symbiont‐based population control strategy

The olive fruit fly Bactrocera oleae is responsible for worldwide economic damage. In this report, we describe the first B. oleae lines transinfected with the Wolbachia strain wCer2, an endosymbiont of the cherry fruit fly Rhagoletis cerasi. Immunostaining followed by confocal microscopy, detects high numbers of Wolbachia in embryos as well as in ovarioles and sperm from individuals of both transinfected lines. wCer2 was uniformly distributed in B. oleae egg chambers and the cortex of preblastoderm embryos. Wolbachia is known to manipulate host reproduction with several strategies, one of which is cytoplasmic incompatibility (CI), resulting in embryonic mortality in incompatible crosses. Wolbachia was found to induce complete CI in the novel host, suggesting that symbiont‐based approaches can be used as novel environmentally friendly tools for the control of natural olive fruit fly populations.     

Comparative evaluation of two olive fruit fly parasitoids under varying abiotic conditions

Psyttalia lounsburyi (Silvestri) and P. humilis (Silvestri) (Hymenoptera: Braconidae) were evaluated in California for their potential to control the invasive olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae). Psyttalia lounsburyi is a specialist on B. oleae while P. humilis also attacks other tephritid species. Field cage trials, conducted from 2006 to 2009, were used to compare P. lounsburyi and two populations of P. humilis (Kenya and Namibia) in California’s interior valley and coastal regions. Both parasitoid species reproduced on B. oleae in all trials. Under similar abiotic conditions, offspring production per female was higher in P. humilis than in P. lounsburyi, suggesting that host specificity by P. lounsburyi does not confer a higher efficiency on B. oleae in cultivated olives. Two abiotic factors were shown to impact parasitoid efficiency. First, adult parasitoid survival was poor during periods of high summer temperatures, common to the olive production areas in California’s interior valleys. Second, parasitism levels were lower on B. oleae larvae feeding in larger Ascolano cv. fruit than in smaller Manzanillo cv. fruit. Results are discussed relative to biological control of B. oleae in commercial olives and the usefulness of natural enemies specialized to attack fruit flies in wild olives compared with the larger cultivated olive fruit.     

Relation of fruit color,elongation, hardness,and volume to the infestation of olive cultivars by the olive fruit fly,Bactrocera oleae

The susceptibility of olive cultivars to the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), has seldom been studied. This article examines factors associated with olive fruit fly infestation of 16 commonly planted Sicilian olive cultivars. Total infestation data were simultaneously correlated with categorical and quantitative factors using ordinal logistic regression. When all factors were included in the analysis, year, sampling date, cultivar, and fruit color were highly significant, but the quantitative factors fruit volume, fruit elongation, and fruit hardness were not. When the analysis was repeated excluding cultivar, all quantitative factors were significant, and elongation and volume were highly significant. Spherical, large, and hard fruit seemed to be preferred by B. oleae over fruit that are elongate, small, and soft. Therefore, fruit color, elongation, volume, and hardness provide useful information regarding the susceptibility of cultivars. In both organic and conventional olive cultivation, information about olive cultivar susceptibility to olive fruit fly will help orchard managers to produce quality oil and table olives while reducing treatments for olive fruit fly control.     

A kaolin‐based particle film for suppression of the olive fruit fly Bactrocera oleae Gmelin (Dip., Tephritidae) in olive groves

The efficacy of a kaolin‐based particle film formulation M‐99‐099 to control olive fruit fly, Bactrocera oleae Gmelin, field infestations was investigated in north‐western Syria. The results showed that fruit infestation levels were significantly reduced on kaolin‐treated trees compared with untreated trees. Kaolin particle film successfully suppressed B. oleae populations and provided season‐long insect control (>14 weeks) whereas the insecticide dimethoate failed to protect olives for as long a period after the last spray. Consistent with previous findings, the M‐99‐099 kaolin particle film proved to be a promising alternative method to synthetic insecticides and could be used to control B. oleae in olive groves.     

Olive fruit fly [Bactrocera (Dacus) oleae (Rossi) (Diptera: Tephritidae)] adult rearing diet without antibiotic

The olive fruit fly [Bactrocera (Dacus) oleae (Rossi) (Diptera: Tephritidae)] adult diet since its development in the 1960’s regularly incorporates antibiotic. Considering recent findings on the importance and function of the indigenous microbial flora of insects, the effects of antibiotic removal were measured on the survival and egg laying of wild flies derived from McPhail trappings and from field infested olive fruits. In the first case wild flies fed no antibiotic laid significantly greater numbers of eggs for two generations (in 5 out of 10 and 2 out of 10 counting dates for G1 and G2 respectively), while there were no significant differences in survival in either test (P = 0.221 for P generation, P = 0.988 for G1 generation from McPhail traps, P = 0.056 for flies from infested fruits). Percent egg–pupa recovery and adult emergence were not significantly affected by lack of antibiotic. An antibiotic‐free strain has been maintained for eight generations, showing acceptable performance when compared to the long‐reared standard ‘Laboratory’ strain. Overall results suggest the feasibility of an adult diet free of antibiotic without negative effects on colony survival and performance.     

Beneficial effect of supplementing an artificial diet for Amblyseius swirskii with Hermetia illucens haemolymph

Artificial diets have been developed to sustain the mass rearing of a wide range of arthropod natural enemies, with varying success. In some cases, such diets can be optimized using insect‐derived materials, such as haemolymph. In this study, we examined the effect of supplementing haemolymph of the black soldier fly, Hermetia illucens, to a basic artificial diet for the phytoseiid mite Amblyseius swirskii. The survival, development and reproduction of the predatory mite were assessed when fed on artificial diets composed of honey, sucrose, tryptone, yeast extract and egg yolk, supplemented with 5%, 10%, or 20% of H. illucens pre‐pupal haemolymph. Developmental time from larva to adult was shorter for males and females offered artificial diets supplemented with 20% haemolymph vs. the basic diet. The oviposition rate and total fecundity of females reared on the basic diet were substantially lower than those of females supplied with the enriched diets. The intrinsic rate of increase was highest on the diet containing 20% haemolymph, followed by those containing 10% and 5% haemolymph. In a subsequent diet‐switching experiment, mites fed on the basic diet in their juvenile stages were switched upon adulthood to diet enriched with different concentrations of H. illucens haemolymph. The females that were fed with the enriched diets from the adult stage on had higher oviposition rates and fecundities than those maintained on the basic diet, but their reproductive parameters were not significantly affected by the concentration of the haemolymph in the artificial diet. In conclusion, supplementing artificial diets with black soldier fly haemolymph significantly improved their nutritional value for A. swirskii. Our findings indicate the potential of using H. illucens as a cheap source for haemolymph in artificial diets, as the fly can be cost‐effectively produced at a large scale on organic waste materials.     

Manipulation of insect gut microbiota towards the improvement of Bactrocera oleae artificial rearing

Bactrocera oleae (Rossi) (Diptera: Tephritidae) is the main pest of olive trees (Olea europaea L.), causing major damages in olive crops. Improvement of mass rearing is a prerequisite for the successful development of large-scale sterile insect technique (SIT) applications. This can be achieved through the enrichment of artificial diets with gut bacteria isolates. We assessed the efficiency of three gut bacteria previously isolated from Ceratitis capitata (Wiedemann), and four isolated from B. oleae, as larval diet additives in both live and inactivated/dead forms. Our results showed that dead Enterobacter sp. AA26 increased pupal weight, whereas both live and dead cells increased pupal and adult production and reduced immature developmental time, indicating that its bacterial cells serve as a direct nutrient source. Live Providencia sp. AA31 improved pupal and adult production, enhanced male survival under stress conditions, and delayed immature development. Dead Providencia sp. AA31, however, did not affect production rates, indicating that live bacteria can colonize the insect gut and biosynthesize nutrients essential for larval development. Live and dead Bacillus sp. 139 increased pupal weight, accelerated immature development, and increased adult survival under stress. Moreover, live Bacillus sp. 139 improved adult production, indicating that Bacillus cells are a direct source of nutrients. Dead Serratia sp. 49 increased pupal and adult production and decreased male survival under stress conditions whereas live cells decreased insect production, indicating that the live strain is entomopathogenic, but its dead cells can be utilized as nutrient source. Klebsiella oxytoca, Enterobacter sp. 23, and Providencia sp. 22 decreased pupal and subsequent adult production and were harmful for B. oleae. Our findings indicate that dead Enterobacter sp. AA26 is the most promising bacterial isolate for the improvement of B. oleae mass rearing in support of future SIT or related population suppression programs.     

Effect of bacteria on nutritional status and reproductive success of the Mediterranean fruit fly Ceratitis capitata

Abstract.  Mediterranean fruit flies ( Ceratitis capitata Wiedemann, Diptera: Tephritidae) harbor a community of diazotrophic bacteria in their digestive system. The present study aims to test the hypothesis that bacteria contribute to fly fitness by enhancing copulatory success and egg production in males and females, respectively. After eclosion, flies were fed a full diet containing peptides, sugar and minerals, or a sugar diet, lacking peptides. Subgroups from each diet were fed a mixture of the antibiotics ciprofloxacin and piperacillin. The presence of bacteria, food consumption, weight gain, lipid and protein levels, oviposition in females and copulatory success of males were quantified in the four groups. The antibiotic treatment effectively cleared the gut of bacteria. The relative amounts of food consumed (with or without antibiotics) are similar in all groups. The antibiotics do not inhibit feeding, and their ingestion does not affect dry weight or the amount of protein stored, yet females feeding on the full diet without antibiotics have increased lipid levels. Females fed the full diet produce significantly more eggs than females on the sugar diet, but the presence of bacteria does not affect numbers of eggs produced. However, in the absence of bacteria, the oviposition rate of nutritionally stressed females is significantly accelerated. The presence of bacteria in sugar fed males does not provide them with a mating advantage. Conversely, in males fed a full diet, the presence of bacteria is associated significantly with a shorter latency to mate. It is concluded that, because the bacterial community is present at all stages of the fly's life cycle, at least some species are effectively transmitted from parents to offspring, and removal of bacteria affects measurable physiological and behavioural parameters related to fitness, the association between bacteria and the medfly is mutualistic.     

Flower nitrogen status and populations of Frankliniella occidentalis feeding on Lycopersicon esculentum

Alighting and capture of wild olive fruit flies, Bactrocera oleae (Rossi) (Diptera, Tephritidae), on spheres of seven different colours was studied on Chios island, Greece. The 70-mm-diam plastic spheres, coated with adhesive, were suspended on olive trees. Yellow and orange spheres trapped the greatest number of males while red and black spheres trapped the greatest number of females. White and blue spheres were the least effective for both sexes. Peak captures occurred in the late afternoon and especially around sunset. Since mating takes place in the last hours of the photophase, the increased captures during that period may be related to the sexual behaviour of the fly. When red spheres were assessed against glass McPhail traps baited with 2% ammonium sulphate, which consist a standard tool for monitoring the olive fruit fly in Greece, there were no significant differences in male captures. However, spheres trapped almost three times as many females as McPhail traps. The possible mechanisms underlying colour discrimination, the motivation of alighting flies and the possible use of red spheres for monitoring and controlling B. oleae are discussed.