Rhagoletis Completa Research Articles

Avermectin Trunk Injections: A Promising Approach for Managing the Walnut Husk Fly (Rhagoletis completa)

This study examined the larvicidal effect of trunk-injected abamectin and emamectin benzoate against the walnut husk fly (Rhagoletis completa Cresson, 1929). Walnut trees in two locations in two years were injected with the pesticides at different concentrations. For the toxicokinetic studies, the active ingredient content was measured in the leaves, flowers, husks, and kernels, using a UHPLC-MS/MS analytical method. The walnut husk fly infestation rates were between 3 and 70% and 10 and 34% for abamectin and emamectin benzoate, respectively, and were much lower compared to those measured for the control. The active ingredient content in the walnut husk showed a positive correlation with the larvicidal effect. The injections had a measurable but unsatisfactory insecticidal effect in the second year, when the economic threshold was exceeded. Trace amounts of the active ingredients were detected in the flowers. The residue analysis showed a declining concentration trend in the leaves over time. The largest quantities were detected in the leaves (≤439 ng/g of abamectin; ≤19,079 ng/g of emamectin benzoate), with concentrations in the husks of orders of magnitude lower (≤5.86 ng/g; ≤50.19 ng/g). The measurements showed no active ingredient residue above the MRLs in either fresh or dried kernels. The results indicate that trunk injections of abamectin, as well as trunk injections of emamectin benzoate, have the potential to suppress walnut husk fly populations.

Host plant stimuli effects on survival and duration of dormancy of Rhagoletis zoqui, Rhagoletis completa (Diptera: Tephritidae) and associated parasitoids.

Tephritid fruit flies in the genus Rhagoletis bridge between predictable periods of fruit availability by becoming dormant. To cope with acyclic unpredictable events (e.g., frost, mast seeding, etc), a proportion of the population can undergo prolonged dormancy. In the case of walnut infesting Rhagoletis, host plant-derived cues such as juglone soil concentration vary seasonally in predictable patterns. Here, we examined the effects of host plant parts and derived compounds on emergence rates and dormancy duration of Rhagoletis completa (Cresson), Rhagoletis zoqui (Bush) (Diptera: Tephritidae), and associated parasitoids. Pupae of both species were exposed to walnut leaves, fruit, or fruit and leaves and compared to a control. In a second experiment, R. zoqui were exposed to 10 mg l-1 of juglone applied to pupation medium during four consecutive 4-week time periods under variable combinations of temperature and frequency of exposure. Overall, the presence of fruit resulted in greater overwintering survival of R. completa but had no effect on the duration of dormancy of either fly species. Application of juglone over two consecutive periods produced greater mortality of R. zoqui than the control. Three parasitoid species emerged from R. completa and one from R. zoqui. Duration of dormancy for parasitoids was longer than that of fly hosts. Regardless of treatment, 13.3-18.4% of R. completa pupae and 1.3-2.8% R. zoqui engaged in prolonged (>year) dormancy. Our results indicate that host plant derived cues have little or no effect on survival and duration of dormancy of walnut infesting Rhagoletis, and at the tested concentration juglone is toxic to R. zoqui pupae. Testing the effect of juglone at lower concentrations is necessary to rule out its role as an environmental cue for regulation of dormancy. So far, host plant fruiting phenology appears to play a greater role than host plant derived cues in selecting for fly eclosion times.

Rhagoletis completa (walnut husk fly)

This datasheet on Rhagoletis completa covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Natural Enemies, Impacts, Prevention/Control, Further Information.

Physical characteristics of walnut husk in relation to infestation by walnut husk fly (Rhagoletis completa)

Physical characteristics of walnut husk in relation to infestation by walnut husk fly (<i>Rhagoletis completa</i>)

Hybridization, Behavioral Patterns, and Pre- and Postzygotic Isolation Between Two Recently Derived Species of Walnut-Infesting Rhagoletis Fruit Flies in the Highlands of Mexico.

Episodes of isolation and secondary contact among populations of insects of Nearctic origin during Pleistocene glacial/postglacial climatic cycles had a strong evolutionary influence on the diversity of flies in the genus Rhagoletis in mountainous areas of Mexico. As a series of experiments undertaken to gather support for phylogenetic hypotheses on the origin of three walnut-infesting species in the suavis group, we examined pre- and postzygotic isolation between Rhagoletis completa Cresson, 1929 and R. ramosae Hernández-Ortiz, 1985. Despite morphological, biological, and behavioral differences, these two species were found to be capable of hybridization. Mating experiments in large enclosures revealed asymmetric sexual isolation. There were notable differences in male sexual behavior. While R. ramosae males mated exclusively on host fruit, R. completa males used fruit and alternative mating locations. During fruit-guarding and male-male contests, R. completa and R. ramosae males adopted markedly different wing postures. R. completa females were more reluctant to copulate with heterospecific males than R. ramosae females. During no choice crosses in small enclosures, there was a reduction of egg hatch for the hybrid cross of R. completa males × R. ramosae females. Our results and previous studies on reproductive isolation between other species pairs in the suavis group support a clade in which R. ramosae, R. zoquiBush, 1966, and R. completa are close relatives all still capable of hybridizing.

How much walnut husk fly (Rhagoletis completa Cresson) affects nut quality of different walnut cultivars?

How much walnut husk fly (Rhagoletis completa Cresson) affects nut quality of different walnut cultivars?

The Effect of Winter Length on Duration of Dormancy and Survival of Rhagoletis completa (Diptera: Tephritidae) and Associated Parasitoids From Northeastern Mexico.

The walnut husk fly Rhagoletis completa (Cresson), native to the Midwestern United States and Mexico, is invasive in California and Europe. It is one of the most important pests of walnuts in areas gathering 30% of the world production. Knowledge of life-history regulation is important for the design of management strategies. Research on dormancy has been performed on invasive populations, and not on populations at the southern extreme of its native range. Here, we examined the effect of winter length on fly and parasitoid emergence, survival, and duration of dormancy. Percent emergence was higher for chill periods at 5°C ranging from 8 to 20 wk. No or insufficient chill resulted in low emergence and a significant proportion of individuals in prolonged dormancy (>1 yr). Duration of dormancy was longer for pupae at constant temperatures and a 4-wk chill period than longer winter durations. Dormancy was longer for Mexican than that reported for U.S. populations, suggesting the existence of a latitudinal cline where populations at southern latitudes have evolved slower metabolic rates. Three parasitoid species were found associated with R. completa (Aganaspis alujai (Wharton and Ovruski) (Hymenoptera: Figitidae), Diachasmimorpha juglandis Muesebeck, and Diachasmimorpha mellea Gahan) (Hymenoptera: Braconidae). Results suggest that rearing of R. completa is possible by subjecting pupae to chill periods between 8 and 20 wk. Overwintering mortality of flies and A. alujai could be further reduced above 5°C. Our findings can contribute for the accurate development of predictive models on invasion potential, development, fly and parasitoid rearing, and biological control.

Altitude affects the distribution and abundance of two non‐native insect pests of the common walnut

AbstractThe leaf miner Coptodisca lucifluella and the carpophagous Rhagoletis completa, of American origin, are two non‐native walnut (Juglans spp.) pests in Italy. For the Friuli Venezia Giulia region (FVG) (N‐E Italy), C. lucifluella is not yet listed, while R. completa has been present for over 25 years. During 2015, samples of leaves and fruits were collected from 219 single old common walnut trees (Juglans regia) placed at different altitudes (0–1,073 m a.s.l.) in FVG to detect the distribution and abundance of both pests. Samples of leaf miner larvae and their parasitoids were subjected to mitochondrial DNA analysis for identification. C. lucifluella has been found in 55 out of 219 sites. The species has been identified by typical leaf symptoms and by its DNA barcode. This is the first report of the species for FVG. The leaf miner distribution was negatively correlated with altitude. The species has not been observed at sites over 600 m a.s.l. Larvae were parasitized by native parasitoids identified as belonging to the genus Chrysocharis by morphological features and by DNA barcode. R. completa has been found in 89 out of 165 sites on walnut trees with fruits. The infestation level was very high in lowland localities. At sites over 700 m a.s.l., no infestation was found. Both species are widespread in the region, and their occurrence is significantly affected by altitude. Data suggest that walnut trees could be cultivated in some mountain areas without the need to control R. completa with insecticides.

Sources of Variation in the Adult Flight of Walnut Husk Fly (Diptera: Tephritidae): A Phenology Model for California Walnut Orchards.

A phenology model of the walnut husk fly, Rhagoletis completa Cresson, was developed to more accurately predict the timing of the flight period and optimize management decisions. A data set of 153 orchard years in which adults were trapped throughout the season was used for the development and validation of this model. Data from California Irrigation Management Information System (CIMIS) weather stations were used to match orchard-year datasets with historical climatic data on degree-day (DD) accumulation, winter chill, and winter rainfall. A cumulative Weibull distribution was used to model the relationship between cumulative trap catch and DD accumulation for R. completa in California. The model was used to predict thermal requirements for the start (5% cumulative trap catch) and mid-point (50% cumulative trap catch) of the flight period, which were 1,670 and 2,179 DDs, respectively. The prediction for 50% cumulative trap catch of R. completa in California was much higher than the thermal requirement estimated in Oregon previously (1,751 DDs). Linear mixed effects models were used to evaluate other environmental and orchard-specific factors which could explain the large variation between predicted and observed thermal requirements for both the start and mid-point of the flight period. Latitude, walnut cultivar leaf-out time, orchard age and year, as a continuous variable, all contributed significantly to explain deviations from the predictions of the DD model for individual orchard years. Such factors can be used both to adjust predicted thermal requirements for these two specific and informative stages of the flight period, and to provide a basis for ecological and evolutionary hypotheses.

Effects of temperature and other environmental factors on the post‐diapause development of walnut husk fly Rhagoletis completa (Diptera: Tephritidae)

AbstractTo more effectively manage walnut husk fly Rhagoletis completa (Diptera: Tephritidae), in California walnut orchards, it is important to understand the factors that affect the timing of adult emergence. In the present study, we examine the effects of incubation temperature, pre‐chill and chill durations, latitude, cultivar and size on the post‐diapause development of R. completa puparia. The lower developmental threshold, upper developmental threshold and optimal temperature for puparial development are estimated to be 4, 34 and 26.6 °C, respectively. The thermal requirement for adult emergence after 120 days of chilling is estimated to be 2024 degree days. Percentage adult emergence declines at both higher and lower incubation temperatures. Chill duration at 5 °C for diapausing puparia has a nonlinear negative effect on the thermal requirement but no effect on percentage emergence. Insufficient chilling leads to poor synchronization of adult emergence. Greater pre‐chill duration at room temperature increases the thermal requirement and slightly decreased percentage emergence. Latitude has a negative effect on the thermal requirement. Puparia from northern California black walnut (Juglans hindsii) have a slightly greater thermal requirement than puparia from cultivated walnut (Julgans regia). There is no significant difference in puparial fresh weight or mean thermal requirement between males and females, although the positive correlation between thermal requirement and puparial fresh weight is stronger for females than males. The effects of temperature and other environmental factors on the post‐diapause development of R. completa are discussed in relation to observations from other Rhagoletis species.

Precopulatory mating and postzygotic isolation between two walnut‐infesting species of Rhagoletis from Mexican highlands

AbstractPleistocene glacial and postglacial cycles producing contraction and expansion of temperate habitats have resulted in substantial diversification among several plant and animal taxa of Neararctic origin undergoing periods of isolation and secondary contact in high‐elevation areas of Mexico. One of such groups are walnut‐infesting fruit flies in the genus Rhagoletis (Diptera: Tephritidae), comprised of six recently derived species among which phylogenetic relationships have been difficult to unravel using conventional molecular methods. Here, we examined pre‐ and postzygotic isolation between two genetically similar and morphologically distinct species which are currently parapatric in central Mexico. Local adaptation driven by differences in host plant phenology between Rhagoletis zoqui Bush and Rhagoletis ramosae Hernández‐Ortíz resulted in allochronic isolation. Despite the existence of precopulatory mating isolation, there was a substantial number of hybrid matings in field cages where conspecific and heterospecific males and females were simultaneously released. The bulk of mating activity took place on host fruit. Rhagoletis zoqui females were more reluctant to mate with R. ramosae males than with males of their own species. Distinctive behavioral differences were observed between males during contests, fruit guarding, and approach to conspecifics on fruit. There was also some asymmetric postzygotic isolation, with the hybrid combination of R. zoqui males and R. ramosae females resulting in lower egg hatch than other mating combinations. Results were consistent with those of a phylogenetic study suggesting recent divergence of R. ramosae from Rhagoletis completa Cresson and R. zoqui in the Sierra Madre Oriental and the Mexican Trans Volcanic Belt.

Identification of walnut husk (Juglans regia L.) volatiles and the behavioural response of the invasive Walnut Husk Fly, Rhagoletis completa Cresson

Several European countries are important walnut (Juglans regia L.) producers. However, these countries must contend with the recent introduction of the Walnut Husk Fly, Rhagoletis completa Cresson (Diptera, Tephritidae), which is causing severe economic losses, especially in organic production. Because most Tephritid fruit flies use kairomones in their search for host plants, we hypothesise that this highly specialist species orients toward the volatile blend released by walnut husks. We collected, identified, and quantified the volatile organic chemicals (VOCs) released by walnut husks from the most commonly cultivated variety in France (Franquette). Then, the behavioural response of R. completa toward synthetic odour blends was recorded in dual choice assays conducted in net cages. A total of 26 VOCs were identified, with α-pinene, β-pinene, trans-linalool, eugenol, and tetradecane representing the major constituents. In the dual choice assay, male and female R. completa were strongly attracted to synthetic blend that included most of the identified husk VOCs. When searching for a host plant, R. completa use host fruit kairomones. The potential of these semiochemicals in monitoring and management of this quarantine pest is discussed. © 2017 Society of Chemical Industry.

Walnut husk fly, Rhagoletis completa (Diptera: Tephritidae), invades Europe: invasion potential and control strategies

Rhagoletis completa Cresson (Diptera: Tephritidae) is native to North America and invaded Western Europe in the late 1980s, causing important damage to its principal host, walnut (Juglans spp.). In this review, we summarize the important elements of R. completa’s biology, phytosanitary status and methods used in Europe for its control, and then present the main conclusions associated with a completed risk analysis performed in 2014 to evaluate the dispersion and establishment potential of R. completa in Europe. The walnut husk fly was initially identified in Switzerland (1988) and Italy (1991), from where it spread to at least seven additional countries: France, Spain, Germany, Austria, Croatia, Slovenia and Hungary. R. completa has not reached the limits of its potential distribution. The main dissemination pathways within Europe include: (1) natural adult dissemination; (2) adult hitchhiker behaviour; and, to a lesser extent, (3) transportation of larvae in fresh fruits. R. completa host plants are widely distributed in Europe, either as isolated wild trees or in orchards, favouring the probability of fly establishment in currently fly-free areas. In addition, the European territories where Juglans species are present share biogeographic similarities. In orchards where R. completa is present and uncontrolled, 100% of walnut trees can be infested, causing losses in walnut yields of up to 80%. The negative effect is low (<10% yield loss) under phytosanitary control, although additional costs must also be considered to support specific monitoring for R. completa. The information presented here underlines a strong need for better walnut husk fly monitoring across European countries, as well as for increasing efforts to develop biological methods to control this emerging pest.

Contributions to the 2014 and 2015 flight pattern and damages of Carpomyia schineri Loew.

The fly Carpomyia schineri Loew is a pest of the berries of the feral Rosa canina group but is can also be found in the berries of grown rose cultivars. The larva damages the flesh of the berry, several larvae can develop inside a single berry. It can decrease the quantity and ascorbic acid content of the tea and jam, which are important human ascorbic acid sources during winter. At the same time in trapping experiments the adult can be confounded with adults of the walnut husk fly (Rhagoletis completa Cresson). In collections of berries at several sites in Hungary damage levels ranged from 0.88% to 65.08 %. Based on these damage levels we had the impression that the yellow sticky traps CSALOMON® PALz or PALs baited with the synthetic Rhagoletis lure caught moderate numbers of adults and were not satisfactory for detection, consequently improving trapping methods is necessary in the future.

Alternative Mating Tactics as Potential Prezygotic Barriers to Gene Flow Between Two Sister Species of Frugivorous Fruit Flies

Rhagoletis completa Cresson and Rhagoletis zoqui Bush, are two sister species in the suavis group that were thought to occupy non-overlapping geographical ranges. Recent discovery of a contact zone in North Eastern Mexico where natural interspecific hybrids with intermediate morphotypes can be found has led to laboratory studies in small enclosures that failed to identify the existence of reproductive barriers capable of maintaining the genetic integrity of both species. Because the experimental approach used in such studies could have interfered with natural behavior of flies, a series of additional mating compatibility tests under much less restrictive conditions were performed. Our observations, confirmed the fact that males and females of both species engage in interspecific matings. However, R. completa females were more reluctant to engage in heterospecific matings than R. zoqui females, revealing asymmetries in sexual isolation. Also, careful scrutiny of male guarding behavior and species specific partitioning of mating location unveiled subtle differences that could result in reproductive isolation if reinforced during secondary contact.

Hybridization and sequential components of reproductive isolation between parapatric walnut-infesting sister speciesRhagoletis completaandRhagoletis zoqui

Hybridization can provide a window into how populations diverge to form new species. Here, we confirm hybridization between Rhagoletis completa Cresson, 1929 and Rhagoletis zoqui Bush, 1966, two species of walnut husk-infesting flies that geographically overlap in a narrow area of parapatry in Northeastern Mexico. Rhagoletis completa and R. zoqui are members of a species group (Rhagoletis suavis) that has been hypothesized to speciate in allopatry. Sexual selection has been argued to be a potentially important factor for generating pre-mating isolation among walnut husk flies, because of the differences in wing morphology and body coloration, and the existence of sexual dimorphism within species. However, there was no evidence for pre-mating isolation between R. completa and R. zoqui, based on choice and no-choice mating experiments conducted on adults of fly populations outside the contact zone. There was also no support for reduced fertility of hybrid matings or for F1 inviability; however, F1 hybrids appeared to have lower fertility and F2 offspring have reduced survivorship. Postzygotic isolation in later generation hybrids of mixed ancestry therefore appears to be the first intrinsic barrier to gene flow evolving between R. completa and R. zoqui. We discuss the implications of our results for allopatric speciation in walnut flies and the potential evolutionary fate of R. zoqui and R. completa if they were to come into broad geographic contact in the future. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ••, ••–••.

Normes OEPP EPPO Standards Diagnostics Diagnostic

Normes OEPP EPPO Standards Diagnostics Diagnostic

Fruit fly larval trail acts as a cue in the host location process of the pupal parasitoid Coptera occidentalis

The pupal parasitoid Coptera occidentalis Muesebeck (Hymenoptera: Diapriidae) was reared in the 1970s in California for the biological control of the Walnut husk fly, Rhagoletis completa Cresson (Diptera: Tephritidae) and later introduced into Europe to be used as a biological control agent against fruit flies. Some behavioral aspects relating to the host location process were investigated in the laboratory in order to improve the chance of success in possible biological control programmes. The searching behavior of the female parasitoid was examined in an open arena in order to evaluate the role of larval trails or rotten-fruit trails (walnut) in the host location process. The response of C. occidentalis to four Tephritid hosts was evaluated: the natural host R. completa, the factitious host Ceratitis capitata (Wiedemann) and two fruit flies of economic importance, Rhagoletis cerasi Linnaeus and Bactrocera oleae (Rossi). In order to assess the response of the parasitoid, a number of behavioral parameters were considered, such as: arrestment behavior, resident time, walking distance, linear and angular speed. The larval trails of R. completa, as well as rotten-fruit liquid trails, were clearly detected by C. occidentalis females, even though the species has been reared for more than 80 generations on C. capitata. In addition, bioassays performed with C. capitata larvae showed a good behavioral response of parasitoid females to the larval trails. Finally, R. cerasi and B. oleae larval trails were barely detected in comparison to the traces left by R. completa and C. capitata larvae. The results are discussed in the light of the possible use of C. occidentalis in biological control programmes.

Green fluorescent protein (GFP)-labeling of enterobacteria associated with fruit flies (Diptera: Tephritidae) and persistence in their natural hostRhagoletis completaCresson.

Fruit flies (Diptera: Tephritidae) are a highly successful, widespread group of insects that cause economic damage in agriculture. Data available so far on the composition of the bacterial community associated with their digestive tract indicate that members of Enterobacteriaceae are the species most often isolated. Bacteria naturally occurring in insect guts may be engineered and used to study the spatial and functional interactions of microbes within the insect system and offer one route to meet the demand for novel insect pest management strategies. With this aim we introduced by conjugation the gfp gene carried by the suicide plasmid pTn5gfpmut1 into Klebsiella oxytoca and Raoultella (formerly Klebsiella ) spp. strains isolated from the oesophageal bulb of the fruit flies Ceratitis capitata (Wiedemann) and Rhagoletis completa Cresson, respectively. The GFP-encoding gene was stably maintained in two tested transgenic strains, both originally isolated from R. completa. In one case, GFP-labeled bacterial cells were used to feed larvae and adults of the original host. Genetically modified bacteria were able to colonize the gut of larvae and persisted through all larval instars to pupal stage.

Influence of walnut cultivar on infestation by Rhagoletis completa: behavioural and management implications

The walnut husk fly, Rhagoletis completa Cresson (Diptera: Tephritidae), has recently invaded Switzerland, Austria, Germany, and France, probably crossing the alpine divide after its initial introduction into Italy. Here, the susceptibility of 36 walnut [Juglans regia L. (Juglandaceae)] cultivars to attack by R. completa was studied in an experimental orchard in Switzerland. Walnut cultivars differed significantly in infestation rates; cultivars that produced large, heavy fruit harboured significantly more larvae than cultivars that produced smaller fruit. Pupal weight was significantly influenced by cultivar, but not by any of the physical properties that we measured. For individual fruit within a cultivar, pupal weight was weakly related to fruit weight and infestation level. Adult longevity was correlated with pupal weight and appeared to be favoured in flies that developed in large-fruit cultivars. The longevities of adults recovered from different cultivars differed significantly. The shortest longevity was recorded for flies recovered from Geisenheim 1049 (39.2 ± 2.80 days) and the longest for flies recovered from Sheinovo (68.8 ± 21.75 days). Differences in diapause length were also highly significant and varied between 167 ± 5.1 (Esterhazy III) and 257.4 ± 8.21 days (Mayette). These results suggest that (1) across and within cultivars, walnut husk flies prefer to infest (i.e., they develop better in) large, heavy fruit, and (2) offspring that develop in large fruit are likely to accrue fitness advantages over the offspring of females using smaller fruit. Our results provide the basis for subsequent studies on resource defence by males, as they enable a prediction of which type of fruit males should defend more vigorously.