Comparative demography of a laboratory and a wild strain of the oriental fruit fly, Dacus dorsalis

Host-specific development and survival rates were measured and population parameters computed for both a wild and a laboratory strain of the oriental fruit fly (Dacus dorsalis Hendel) in Hawaii. Gross fecundities of the wild and laboratory strains were 241 and 1551 eggs per female, respectively. Egg to eclosion developmental rates were 27 days for the wild strain and 24 days for the laboratory strain. The preovipositional period of the wild strain was 19 days compared to 9 days in the laboratory strain.Differences of this magnitude in fecundity and developmental rates between laboratory and wild strains have not been observed in other recent demographic studies of tephritids. The results suggest that the laboratory strain of the oriental fruit fly may have undergone more intense selection than laboratory strains of the other species.

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Résumé Pour deux souches, l'une sauvage, l'autre de laboratoire, de D. dorsalis de Hawaï, les mesures ont porté sur la durée de développement et le taux de survie, les paramètres caractéristiques de la population ont été traités sur ordinateur. Pour les souches sauvage et de laboratoire, les fécondités brutes ont été respectivement de 241 et 1551 oeufs par femelle. Les durées de développement larvaire et nymphal ont été de même de 27 jours pour la souche sauvage et de 24 j pour celle de laboratoire; les périodes de latence avant la ponte ont été de 19 j pour la souche sauvage contre 9 j pour celle de laboratoire.Jamais de telles différences de fécondités et de durées de développement entre souches sauvages et de laboratoire n'avaient été observées lors des études récentes sur des téphritidae. Ces résultats suggèrent que la sélection subie par la souche de laboratoire de D. dorsalis été plus intense que celles subies par d'autres espèces.

     

Host-specific demographic studies of the Mediterranean fruit fly Ceratitis capitata

Abstract. 1. This study was conducted in Greece using a wild strain of medflies ( Ceratitis capitata [Weidemann]) to assess age-specific vital rates in adults, and development and survival in pre-adults when reared on different host fruit. The results were used to construct life tables.
2. The demographic analyses suggested that there are basically four aspects of the medfly's life history which are of major importance: (i) multiple, highlyoverlapping generations; (ii) high net reproduction while young; (iii) high larval fitness in certain hosts; (iv) lack of diapause.
3. Reasons why these characteristics are felt to be important are briefly discussed.     

Scale‐appropriate spatial modelling to support area‐wide management of a polyphagous fruit fly (Diptera: Tephritidae)

Control of mobile pests frequently requires area‐wide management (AWM) that spans commercial and non‐commercial habitats. Spatial modelling of habitat suitability can guide investment and implementation of AWM, but current approaches rarely capture population drivers, including local foraging, at an appropriate spatial resolution. To support the development of AWM for the fruit fly pest, Bactrocera tryoni (Tephritidae), we developed a habitat suitability model for the three premier fruit‐growing regions in south‐eastern Australia (~34,780 km²). Expert elicitation and published literature was used to develop a Bayesian network to model the drivers of B. tryoni habitat suitability, as determined by the ability of populations to persist and increase. The effect of uncertainty was tested through sensitivity analysis. The model was then linked with spatially explicit data (at 10 m resolution) to generate risk maps, using moving windows to capture local foraging movement. Habitat suitability was most strongly influenced by host availability within a distance of 200 m. Climate stress, and soil moisture for pupation, was also limiting. Experts were uncertain regarding the relative importance of drivers of host availability (host preference, host density, fruit seasonality), but this did not greatly affect model outputs. Independent trapping data supported model predictions, but their value was limited as traps were placed almost exclusively in optimal or suitable habitat. Amenability to AWM, when assessed as the ratio of suitable or optimal habitat that was under non‐horticultural versus horticultural land‐uses, differed by region (0.15–1.17). However, risk‐mapping did identify where ratios were locally most favourable (lowest). Also, predominantly local dispersal by B. tryoni suggests AWM for pest suppression could be applied at a landscape‐scale. Results show that a relatively simple model could capture the multi‐scale drivers of population dynamics and the complexity of landscapes sufficiently to guide AWM of a mobile pest.     

Population dynamics of the oriental fruit fly, Bactrocera dorsalis （Diptera： Tephritidae） in the Kunming area,southwestern China

Population dynamics of Bactrocera dorsalis Hendel （Diptera： Tephritidae） were studied through pheromone trapping over 4 years （1997, 1999, 2000, 2003） in the Kunming region, a high plateau area in southwestern China. B. dorsalis immigrates from southern Yunnan to Kunming each year, and occurs during early May through November. Annual trap captures recorded an increase in the B. dorsalis populations from May to July, when they peaked in abundance, and a decline until November. No flies were detected from November to April. The fruit flies had two generations. There was considerable overlapping due to the continuous arrival of immigrating flies during the summer months. Annual capture rates were significantly related to numbers of flies caught in July when peak captures were recorded; whereas the peak captures, in turn, positively depended on numbers of flies recorded in May, the first month of fly appearance in the current year. It suggested that the annual population abundance was mainly dependent on the size of the initial emigrating population. A daily average temperature of 18℃ was probably the threshold temperature required for the flies to undertake long-range dispersal, which partially explained the start of the fly in May each year on this high plateau. Under field conditions, the fruit flies can withstand 13℃ as a daily average temperature. No flies were recorded in any of the study years at a daily temperature colder than 10 ℃.     

Age and host effects on clutch size in the Mexican fruit fly, Anastrepha ludens

We document individual and age-specific variation in reproductive output and clutch size of Anastrepha ludens Loew. (Diptera: Tephritidae). The influence of host size, color, and density on clutch size are also examined. Individual and groups of flies were offered artificial hosts composed of agar spheres wrapped in Parafilm. The gross reproduction rate of individual flies was 1000 eggs/female and 165 clutches/female with a range of 1 to 40 eggs/clutch. Mean clutch sizes for these females ranged from 4.5 to 10.6 eggs/clutch. The number of eggs/clutch laid by females held in groups was highly correlated with host size, ranging from about 4.4 eggs/clutch in 2 cm diameter hosts to 12.7 eggs/clutch in 11 cm hosts. Host color, host density, fly density, and fly age did not affect clutch size. This study suggests that variation among females and host size are the principal determinants of clutch size in A. ludens.

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Résumé L'examen a porté sur l'influence du polymorphisme et des modifications dues à l'âge des mouches sur la fécondité et la taille des pontes de A. ludens Loew (Dipt. Tephritidae). L'étude a concerné aussi l'influence de la dimension, de la couleur et de la densité des hôtes sur la taille des pontes. Des mouches isolées ou par groupes ont reçu des hôtes artificiels formés de sphères d'agar enveloppées dans du parafilm. La fécondité brute de femelles isolées a été de 1000 oeufs/femelle et de 165 pontes/femelle, avec une variation de 1 à 40 oeufs/ponte. La taille moyenne des pontes des différentes femelles isolées s'étalait de 4,5 à 10,6 oeufs/ponte. Le nombre d'oeufs/ponte des femelles groupées était fortement liée à la dimension de l'hôte, s'étalant de 4,4 oeufs/ponte pour des hôtes de 2 cm de diamètre à 12,7 oeufs/ponte pour ceux de 11 cm de diamètre. Ni la couleur et la densité des hôtes, ni la densité et l'âge des mouches n'ont influé sur la taille des pontes. Ces résultats suggèrent que les variabilités du comportement des femelles et de la dimension des hôtes déterminent par priorité la taille des pontes de A. ludens.

     

Effects of macronutrient intake on the lifespan and fecundity of the marula fruit fly,Ceratitis cosyra (Tephritidae): Extreme lifespan in a host specialist

In insects, lifespan and reproduction are strongly associated with nutrition. The ratio and amount of nutrients individuals consume affect their life expectancy and reproductive investment. The geometric framework (GF) enables us to explore how animals regulate their intake of multiple nutrients simultaneously and determine how these nutrients interact to affect life‐history traits of interest. Studies using the GF on host‐generalist tephritid flies have highlighted trade‐offs between longevity and reproductive effort in females, mediated by the protein‐to‐carbohydrate (P:C) ratio that individuals consume. Here, we tested how P and C intake affect lifespan (LS) in both sexes, and female lifetime (LEP), and daily (DEP) egg production, in Ceratitis cosyra, a host‐specialist tephritid fly. We then determined the P:C ratio that C. cosyra defends when offered a choice of foods. Female LS was optimized at a 0:1 P:C ratio, whereas to maximize their fecundity, females needed to consume a higher P:C ratio (LEP = 1:6 P:C; DEP = 1:2.5 P:C). In males, LS was also optimized at a low P:C ratio of 1:10. However, when given the opportunity to regulate their intake, both sexes actively defended a 1:3 P:C ratio, which is closer to the target for DEP than either LS or LEP. Our results show that female C. cosyra experienced a moderate trade‐off between LS and fecundity. Moreover, the diets that maximized expression of LEP and DEP were of lower P:C ratio than those required for optimal expression of these traits in host‐generalist tephritids or other generalist insects.     

Comparative population growth and life table demography of the rotifer Asplanchna girodi at different prey (Brachionus calyciflorus and Brachionus havanaensis) (Rotifera) densities

Population growth and life table demography of the predatory rotifer A. girodi using spineless Brachionus calyciflorus and spined Brachionus havanaensis as prey at densities of 1, 2, 4 and 8 ind. ml^–1 at 25°C were studied. Regardless of the prey species, the population of A. girodi increased with increasing availability of Brachionus in the medium. At any given prey density, A. girodi fed B. calyciflorus showed consistently better growth than when fed B. havanaensis. The maximum population densities of A. girodi varied from 0.28 to 1.8 ind. ml^–1 depending on the prey species and the density. The rate of population increase observed in population growth studies varied from 0.17 to 0.43 day^–1 when fed B. calyciflorus and 0.09 to 0.27 day^–1 when fed B. havanaensis. Male population of A. girodi was closely related to female density. The lowest average lifespan was observed for A. girodi when fed B. havanaensis at 1 ind. ml^–1, while the converse was the case when fed B. calyciflorus at comparable prey concentration. Net reproductive rates varied from 16 to 26 offspring female^–1 lifespan^–1 depending on the prey species and concentration. Generation time of A. girodi decreased with increasing food concentrations for both the prey species. The rates of population increase obtained from life table demography were lower for A. girodi when fed B. havanaensis than when fed B. calyciflorus.     

Polymorphic microsatellite markers for population analysis of a tephritid pest species, Bactrocera tryoni

To obtain a set of microsatellite markers for the Queensland fruit fly Bactrocera tryoni , a genomic library was screened with a number of simple repeat oligonucleotide probes. Sequencing recovered 22 repeat loci. The microsatellite sequences were short, with repeat numbers ranging from five to 11. Of these, 16 polymerase chain reaction (PCR) primer sets yielded amplifiable products, which were tested on 53 flies from five widely separated sites. All loci showed polymorphism in the population sample, with the number of alleles ranging from two to 16. Several dinucleotide repeats showed alleles separated by single-base differences and multiple steps, suggesting a mutation process more complex than the stepwise mutation model.     

Effect of insectary rearing on host preference and oviposition behavior of the fruit fly parasitoid Diachasmimorpha longicaudata

Diachasmimorpha longicaudata (Ashmead) has been produced in the laboratory for >160 generations on the larvae of oriental fruit fly, Bactrocera dorsalis (Hendel), the propagation hosts raised routinely on a semi-synthetic wheat diet formulation. Choice tests using modified stinging units were conducted in the laboratory to investigate whether insectary rearing had altered the host seeking and oviposition behavior of female parasitoids. Results showed that fruit fly larvae that developed in papaya, Carica papaya L. var. solo, were less preferred for oviposition than fruit fly larvae that developed on wheat diet when both were exposed concurrently to naive D. longicaudata females (= females without prior oviposition experience). The substrates (pureed papaya or wheat diet) in which treatment larvae were exposed to parasitoids did not affect oviposition preference of gravid D. longicaudata for wheat diet-reared fruit fly larvae. Our study demonstrated the possibility that rearing in an insectary system may have modified the parasitization behavior of female D. longicaudata.     

Effects of depth of oviposition dish and age ofrearing host on efficiency of mass production of thetephritid fruit fly parasitoid Psyttaliafletcheri

Psyttalia fletcheri is a solitary larval endoparasitoid ofthe melon fruit fly, Bactrocera cucurbitae. Initiallycolonized in 1985, mass production of P.fletcheri for the last 10 years has beenfacilitated with a rearing method developed earlier.However, the level of parasitoid recovery seldomexceeded 35%. We examined the parasitoid'sdevelopmental biology and behavior to identify theprocedures that may improve efficiency ofproduction. We found that by limiting the depth ofoviposition dish (receptacle that holds the hostlarvae during exposure to female parasitoids) to 4 mm and using 4-d-old (late 2nd instar) B.cucurbitae larvae for oviposition, parasitoid yieldwas increased two-fold.     

Olfactory receptors in Bactrocera species for sustainable fruit fly management: A review and future perspectives

Molecular studies on odorant receptors (ORs), odorant-binding proteins (OBPs) and the functioning of the receptor and pheromone signal transduction in fruit fly Bactrocera species have expanded exponentially during the past few decades. OBPs contribute to the sensing of the olfactory system (OS) via the transduction of odorants through the sensillum lymph. However, ORs, a family of G-protein-coupled receptors in Bactrocera and various other species, exhibit heightened responsiveness to multiple chemical odours such as hormones, sensory stimuli and neurotransmitters. The apparent mechanism involves a combinatorial code encompassing both peripheral and antennal lobe processing, facilitating the reception of sexual pheromones and environmental cues. The OS is specifically designed to recognize and process information from volatile chemical signals, and these chemical signals play an important function in various flies. Insects rely on these chemicals to navigate and comprehend their surroundings. A mature insect OS is composed of two pairs of sensillae-covered palps, antennae and two primary pairs of olfactory appendages on the anterior head. It has been shown that chemosensory gene families contribute in odour perception. These include various neuroreceptor families, such as OBPs, chemosensory proteins and sensory neuron membrane proteins. Additionally, there are three divergent chemoreceptors, namely ORs, ionotropic receptors and gustatory receptors. Methods based on systematic biology, molecular biology and bioinformatics tools have rapidly emerged to investigate the insect communication systems and provide new insights for the management of many agricultural pest. Several aromatic compounds, including semiochemicals and pheromones, have been employed to defend crops and animals from destructive fruit flies and other invasive and frugivorous species. To promote the expansion of the cropping system, the utilization of phytochemical lures can be convenient for sustainable agriculture production and enhance food security. Hence, this review examined the state of the art in chemical communication of insects with a focus on fruit fly pest species to identify OS and their semiochemical receptors, protein receptors and chemosensory receptors (CSRs), as well as their practical applications for biological control and integrated pest management are highlighted.     

Screening mitochondrial DNA sequence variation as an alternative method for tracking established and outbreak populations of Queensland fruit fly at the species southern range limit

Understanding the relationship between incursions of insect pests and established populations is critical to implementing effective control. Studies of genetic variation can provide powerful tools to examine potential invasion pathways and longevity of individual pest outbreaks. The major fruit fly pest in eastern Australia, Queensland fruit fly Bactrocera tryoni (Froggatt), has been subject to significant long‐term quarantine and population reduction control measures in the major horticulture production areas of southeastern Australia, at the species southern range limit. Previous studies have employed microsatellite markers to estimate gene flow between populations across this region. In this study, we used an independent genetic marker, mitochondrial DNA (mtDNA) sequences, to screen genetic variation in established and adjacent outbreak populations in southeastern Australia. During the study period, favorable environmental conditions resulted in multiple outbreaks, which appeared genetically distinctive and relatively geographically localized, implying minimal dispersal between simultaneous outbreaks. Populations in established regions were found to occur over much larger areas. Screening mtDNA (female) lineages proved to be an effective alternative genetic tool to assist in understanding fruit fly population dynamics and provide another possible molecular method that could now be employed for better understanding of the ecology and evolution of this and other pest species.     

Population persistence of the parasitoid fly Zaira cinerea (Fallén) (Diptera: Tachinidae) utilizing multiple host carabid beetles with different seasonality and quality

Zaira cinerea (Fallén) is a parasitoid fly (Diptera: Tachinidae) that attacks adult carabid beetles. To better understand mechanisms of population persistence in this species, we examined seasonality of host beetle abundance, the frequency of parasitism, and the timing of fly eclosion. In addition, we evaluated host quality using numbers of larvae or puparia per individual beetle as a measure of quality. The fly parasitized only large carabids (≥15 mm body length); the lengths of fly puparia reached 7.4–10.8 mm during development in beetle abdomens, and larger hosts are likely essential. Of the 18 large carabid species collected in this study, we chose two, Carabus maiyasanus Bates and Leptocarabus procerulus (Bates), because they were large and abundant (87% of total catch). The two carabids had different phonologies; C. maiyasanus was abundant from spring to summer, and its abundance dropped sharply in autumn, while L. procerulus was abundant in autumn and rare from spring to summer except July. Parasitism was observed in all the months from May to November except June, and adult flies eclosed more than once a year (in early summer, late summer, and mid‐autumn), indicating that the species is multivoltine. Host quality of L. procerulus was higher than that of C. maiyasanus. Carabus maiyasanus was mainly used as a host from spring to summer, and L. procerulus was used in autumn. Thus, adult beetles of one or both species are available over most of spring, summer, and autumn, allowing population persistence of this fly species over time.     

桔小实蝇和番石榴实蝇对6种寄主果实的产卵选择适应性

植食性昆虫对寄主植物的选择适应性是研究昆虫和植物协同进化关系的核心内容之一。评估寄主植物对植食性昆虫种群的适合度,需要综合分析昆虫对寄主的产卵选择性和寄主对昆虫的取食适合性。以桔小实蝇和番石榴实蝇为研究对象,分别测定了这两种实蝇对6种寄主果实:番石榴、香蕉、杨桃、木瓜、甜橙、番茄的产卵选择性以及幼虫取食后对其生长发育的影响。寄主产卵选择性实验分别采用完整寄主果实直接供试产卵和块状寄主果实气味引诱产卵两种处理方式;在生长发育适应性实验中,以幼虫和蛹的存活和生长发育等相关参数作为评价指标。实验结果表明,寄主的供试方式不同,两种实蝇的选择性均有明显差异;对寄主气味选择性强的寄主更适合于两种实蝇后代的生长发育。两种实蝇对6种寄主果实的产卵选择性和后代发育适合性两者相关性不显著,与许多文献报道单一地采用发育适合性(如发育历期、存活率或蛹重等)作为评价寄主选择性的结果不一致。两种实蝇之间对6种寄主果实的产卵选择和幼虫取食适合性既具相似性也具差异性,表明这两种实蝇在寄主生态位上既有重叠性又有分化性。     

Uncovering the tracks of a recent and rapid invasion: the case of the fruit fly pest Bactrocera invadens (Diptera: Tephritidae) in Africa

Phytophagous insects of the genus Bactrocera are among the most economically important invasive fruit fly pests. In 2003, an unknown Bactrocera species was found in Kenya. First identified as an ‘aberrant form’ of the Asian B. dorsalis complex, it was later recognized as a new species, Bactrocera invadens. Within 2 years of its discovery, the species was recorded in several African countries, becoming an important quarantine pest. As this invasive fly was discovered only recently, no data are available on its invasion pattern in Africa. This pilot study attempts to infer from genetic data the dynamic aspects of the African invasion of this pest. Using microsatellite markers, we evaluated the level of genetic diversity and the extent of common ancestry among several African populations collected across the invaded areas. A sample from the Asian Sri Lankan population was analysed to confirm the Asian origin of this pest. Genetic data cast no doubt that Sri Lanka belongs to the native range, but only a small percentage of its genotypes can be found in Africa. African populations display relatively high levels of genetic diversity associated with limited geographical structure and no genetic footprints of bottlenecks. These features are indicative of processes of rapid population growth and expansion with possible multiple introductions. In the span of relatively few years, the African invasion registered the presence of at least two uncorrelated outbreaks, both starting from the East. The results of the analyses support that invasion started in East Africa, where B. invadens was initially isolated.     

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.     

Implications of host mortality on the economics of Fopius arisanus (Hymenoptera: Braconidae) mass rearing

Fopius (= Biosteres) arisanus (Sonan) (= Opius oophilus Fullaway) is an egg-pupal parasitoid of tephritid fruit flies. Our breakthrough in the development of a laboratory-adapted strain of F. arisanus facilitated insectary rearing of parasitoids in large numbers. First colonized in captivity in 1989, F. arisanus has been reared routinely on the oriental fruit fly, Bactrocera (= Dacus) dorsalis (Hendel), its natural host. Parasitization by F. arisanus results in the latent death of developing hosts. Host mortality data are presented in a life table to estimate cost of parasitization on the economics of F. arisanus mass rearing. Percent kills of 10, 32, and 76% exerted by F. arisanus on the egg, larval, and pupal stages of the rearing hosts, respectively, resulted in a mean parasitoid recovery of 23.6%. The production cost was estimated by integrating life table data with the costs of rearing supplies and materials and personnel-hours requirements. Production of 1 million parasitoid adults requires the exposure of 4.2 million B. dorsalis eggs (= propagation hosts). We estimated the cost of producing 1 million parasitoids to be $2,363.30 and identified the most expensive aspects of F. arisanus rearing. Recommendations for streamlining the rearing process to reduce costs are provided.     

Temperature‐dependent demography of Agriphila aeneociliella (Lepidoptera: Crambidae), a new insect pest of wheat in China

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Population genetic structure of the western cherry fruit fly Rhagoletis indifferens (Diptera: Tephritidae) in British Columbia,Canada

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