TY - JOUR
AU - Verheggen, François, J
AB - Abstract It is important to monitor fruit flies (Diptera: Tephritidae) efficiently to implement sustainable means of control. Attractants are often used to increase the efficiency of sticky traps deployed in orchards to monitor Lepidopterans, but remains to be developed to monitor fruit flies. Rhagoletis completa Cresson (Diptera: Tephritidae) is an invasive species in the walnut orchards of Europe, and is commonly monitored with yellow sticky traps. In this study, we collected the volatile compounds released by male and female R. completa, and identified two lactones released exclusively by males. We then formulated both lactones in long-lasting volatile dispensers, and we quantified their release rate over a 26-d period. Finally, during the entire period when female flies are present in the field, we compared the efficiency of the conventional monitoring method using unbaited yellow sticky traps with yellow sticky traps associated with a dispenser releasing both male-produced lactones. These assays were conducted in 54 walnut orchards in France, in 2017. The number of fruit flies caught with sticky traps associated with lactones dispensers was increased by up to 10 times each week. Lactone-baited traps also allowed earlier detection in the season. These field results are promising for R. completa monitoring. A complete chiral identification of these lactones should be performed along with a clarification of their role in the sexual communication of R. completa. sex pheromone, fruit fly, integrated pest management, walnut Fruit flies of the genus Rhagoletis Loew (Diptera: Tephritidae) are major insect pests, causing important economic damage to orchards. The walnut husk fly, Rhagoletis completa Cresson (Diptera: Tephritidae), is a highly specialized fruit fly that infests Juglans species exclusively (Bush 1966). This fly is native to the central United States and was introduced to California in the 1920s, where it had a significant economic impact on walnut production (Boyce 1934, Barić et al. 2015). In the European Union, walnut production grows every year, representing 79,180 hectares of orchards in 2016 for a total production of 171,575 tons of fruits. The fly was introduced in the EU in the late 1980s (EPPO 2013), starting in Switzerland (1988) and spreading to neighboring countries, including Italy (1991), France (2007), and Spain (2013) (Verheggen et al. 2017). In orchards where R. completa is present and uncontrolled, 100% of walnut trees may be infested, causing up to 80% losses in walnut yields (Verheggen et al. 2017). The larvae feed inside the husk, darkening the kernel and staining the shell (Duso and Lago 2006), which reduces the quality of walnuts (Samietz et al. 2012). The negative effect of the fruit fly is low under phytosanitary control (<10% yield loss). Current control strategies against R. completa include the application of neonicotinoids (e.g., acetamiprid) and/or organophosphates (e.g., phosmet), which are primarily used against the codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae), in conventional orchards. These phytosanitary treatments are implemented within the framework of the monitoring efforts performed by each farm. In most countries in Western Europe, including France, yellow sticky traps are placed inside orchards and must be checked twice a week. They are not baited with attractants and capture flying insects that are attracted to the color yellow. Phytosanitary treatments are initiated 10 d after the first capture, if three consecutive captures are recorded. As a consequence, it is important that the monitoring method captures flies as soon as they emerge, since early phytosanitary treatments reduce final pest damages. Pheromones have proven effective for monitoring and/or controlling a broad range of insect pests of fruit trees (Light 2016). In walnut orchards, codlemone was successfully used to improve the monitoring of C. pomonella (Liu et al. 2016). In this study, we aimed to identify sex-specific volatiles of R. completa and to evaluate their ability to improve the monitoring efficiency of the currently used sticky traps. Our results are expected to advance current field-monitoring techniques of fruit flies in walnut orchards and other fruit orchards. Methods and Materials Insect Collection and Rearing R. completa pupae were collected from Juglans regia orchards in Chatte (South of France; Lambert 93 coordinates: X: 8794 hectometers Y: 64520 hectometers) in October 2016. Adult males and females were separated on the day of emergence and were kept in net cages containing food (yeast hydrolysate and sugar) and water in a level 2 quarantine (L2Q) insect laboratory. The room conditions were set at 25 ± 2°C, 65 ± 5% relative humidity (RH) and a 16-h light photoperiod. These conditions were continuously controlled with a datalogger (EasyLog USB-2; Lascar Electronics, Wiltshire, United Kingdom). Collection and Identification of Volatiles Five newly emerged fruit flies (five males or five females aged 3–6 d) were placed in a 20-ml vial. A Solid Phase Micro-Extraction (SPME) fiber (Polydimethylsiloxane/ Divinylbenzene/ Carboxen) (Sigma Aldrich, Bornem, Belgium) was then inserted in the vial for 24 h (Levi-Zada et al. 2012). The fiber was previously wrapped with a net to prevent flies from touching the fiber. Five replications were conducted for both males and females. The SPME fiber was analyzed in a GC-MS (model 6890n GC System/5973; Agilent Technologies, Santa Clara, CA) immediately after the end of sampling. The collected volatiles were separated on an HP5-MS capillary column (30 m × 0.25 mm I.D.; film thickness 0.25 mm) under splitless conditions at 300°C. The oven temperature program started at 40°C, held for 2 min, then programed at 4°C/min to 95°C, then at 6°C/min to 155°C, and finally at 25°C/min to 280°C, with final hold at this temperature for 5 min. The mass spectra were recorded in the electron impact mode at 70 eV (source at 200°C, transfer line at 250°C, scanned mass range: 39 to 300 m/z). The compounds were identified by interpreting the mass spectra and by co-injection of pure molecules. Recorded MS data were also compared to the computed WILEY 275.L spectral library. Semiochemical Blend and Release Calibration Before conducting field assays, we formulated the identified volatile compounds in long-lasting volatile dispensers and quantified the amount of volatiles being released over a 26-d period. The volatile compounds included in the dispensers consisted in the two lactones identified in male emissions. The lactone dispenser consisted of a rubber septum (7.1 mm I.D.; VWR International Europe BVDA, Leuven, Belgium) loaded with 50 µl delta-hexalactone and 50 µl delta-heptalactone (both were identified from the headspace of R. completa males) diluted in 100 µl diethyl ether solution. The solvent was allowed to evaporate for 10 min before placing a second rubber septum on the first one. The second septum reduces the evaporation of the volatile compounds and allows a constant release (Censier et al. 2016). Rubber septa were placed outside during a 26-d period. During that period, they were not directly exposed to the sun and were exposed to a mean temperature of 19.2°C and a mean relative humidity of 62%. Every day, the volatile release rate was evaluated using a volatile collection method. Each day rubber septa were placed inside clean glass chambers (1 liter) for 30 min, and charcoal-purified air was pulled through the chamber by a vacuum air pump that provided a constant flow rate set at 600 ml min−1. Two glass tubes filled with 60 mg HayeSep Q (co-polymer of ethylvinylbenzene and divinylbenzene) (80/100 mesh; Hayes Separation Inc., Houston, TX) were used to collect the volatile chemicals released in the headspace of the glass chambers. Before all assays, the glass chamber and all the PTFE pipes were washed with an Extran solution (MA 01; Merck, Darmstadt, Germany). After volatile collection, both filters were eluted with pure n-hexane (200 µl) formerly dosed with an internal standard (n-butylbenzene, at 86 ng μl−1). The rubber septa were then placed back outside until the next day. For quantification purposes, an aliquot of 1 µl n-hexane extract was injected in a GC-FID (Thermo Scientific, Interscience, Louvain-la-Neuve, Belgium) on a chiral Lipodex E column (25 m × 0.25 mm I.D.; film thickness 0.25 mm; Macherey Nagel, Düren, Germany). The oven temperature program started at 60°C, was held for 2 min, and was increased at 5°C min−1 to 190°C. The calibration method used to quantify the volatile compounds was carried out according to the validated method described by Heuskin et al. (2009). n-Butylbenzene (purity > 99.9%, Sigma-Aldrich, Bornem, Belgium) was used as an internal standard at 8.6 ng μl−1 at each concentration level. To generate the calibration curve, five standard solutions (from 1 ng μl−1 to 100 ng μl−1 of delta-hexalactone and delta-heptalactone) and blanks were injected as data points and analyzed in three replicates. The injections were repeated twice more for the central point of the curve (i.e., the solution at 10 ng μl−1). The calibration curve was obtained by plotting the ratio of the analyzed peak area/internal standard peak area versus the analyte concentration. The method of least squares fit was used to calculate the calibration curve. Linearity was considered satisfactory when the correlation exceeded 0.996. Field Experiments During the summer of 2017, we conducted a field assay to compare the efficiency of two R. completa monitoring traps: 1) a chromatic yellow trap (20 × 40 cm) without any lure (Bug-Scan, BioBest, Westerlo, Belgium); and 2) a chromatic yellow trap associated with a volatile dispenser releasing both identified lactones. We also included in the field assay a mass trapping system (Decis trap, Bayer, Paris, France) baited with insecticide and food attractant (deltamethrin, ammonium acetate, trimethylamine chlorydrate, 1,5-diaminopentane), and recommended by the manufacturer for fruit flies trapping. We decided to include this mass trapping system to compare the attractiveness of both yellow sticky traps with a different physical setup (e.g., large volume) baited with food attractant. The numbers of R. completa captured by all three traps were compared. One trap of each type was placed in each 54 orchards (i.e., three traps per site) distributed in the south east of France around the Station Expérimentale Nucicole de la Région Rhône-Alpes (SENuRA, Chatte, France). Each trap was separated from the other traps by 25 m and was hung on a tree at 6 m above the ground. The number of flies trapped was monitored twice a week in each orchard during a 10-wk period. The Bug-Scan traps were renewed when saturated. Every 3 wk, the lactone dispensers were replaced. The Decis traps were cleared out twice a week, but the lure was not changed since it was designed to be active throughout the season by the manufacturer. A generalized linear mixed model, conducted with R software (v. 3.4.2) (R Development CoreTeam 2005) was conducted to compare the mean number of flies caught on each trap. Statistical analyzes were performed on the data of the bi-weekly surveys. Results Collection and Identification of Volatiles While no volatile chemical could be identified from the female R. completa headspace, two chemical compounds were identified from the headspace of male R. completa in all replicates; namely, delta-hexalactone (CAS 823-22-3) and delta-heptalactone (CAS 3301-90-40) (Fig. 1). Both compounds were released in variable proportions, with a mean proportion of 40/60 (delta-hexalactone/delta-heptalactone). Fig. 1. Open in new tabDownload slide Chromatogram of both R. completa gender with chemical structures of (a) delta-hexalactone and (b) delta-heptalactone; *represents the chiral center. Fig. 1. Open in new tabDownload slide Chromatogram of both R. completa gender with chemical structures of (a) delta-hexalactone and (b) delta-heptalactone; *represents the chiral center. Estimation of Release Rates The release dynamic was similar for delta-hexalactone and delta-heptalactone (Fig. 2). Following an initial increase in volatile emission rate during the first 4 d, the release rate was constant for 20 d, before decreasing. Based on these emission profiles, we decided to place 4-d-old rubber septa in the orchards and to replace them after 22 d. Fig. 2. Open in new tabDownload slide Dynamic release of the two compounds: (a) delta-hexalactone cumulative emission; (b) delta-heptalactone cumulative emission. Solid line represents mean of the four replicates. Dotted lines represent the confidence interval. Fig. 2. Open in new tabDownload slide Dynamic release of the two compounds: (a) delta-hexalactone cumulative emission; (b) delta-heptalactone cumulative emission. Solid line represents mean of the four replicates. Dotted lines represent the confidence interval. Field Experiments The total numbers of R. completa trapped over the entire field assay on the three traps are presented in Fig. 3. More flies were trapped on the yellow sticky traps baited with lactones compared with non-baited yellow sticky traps (P < 0.0001) and the Decis trap (P < 0.0001). Fig. 3. Open in new tabDownload slide Mean (±SE) capture of Rhagoletis completa per week when using the three different types of traps. Fig. 3. Open in new tabDownload slide Mean (±SE) capture of Rhagoletis completa per week when using the three different types of traps. During the first week of the season, lactone-baited traps enabled fly detection in 40% of orchards, while the unbaited traps detected flies in only 12% of the orchards (Fig. 4) (week 1: χ2 = 20.37; week 2: χ2 = 20.51; week 3: χ2 = 10.6). With R. completa population increasing, the difference between both traps (i.e., lactones-baited and unbaited traps) has diminished over time, from 28% on week 1 to 23% on week 3. Fig. 4. Open in new tabDownload slide Frequencies of orchards with R. completa captures based on non-baited yellow traps (dotted area) and lactone-baited traps (hatched area). Blank area correspond to orchards with no fly capture. Areas where both dots and stripes occur represent orchards where both traps. Fig. 4. Open in new tabDownload slide Frequencies of orchards with R. completa captures based on non-baited yellow traps (dotted area) and lactone-baited traps (hatched area). Blank area correspond to orchards with no fly capture. Areas where both dots and stripes occur represent orchards where both traps. Because phytosanitary treatments are initiated if three consecutive captures are made, we calculated the number of orchards where treatments would have been applied based on the number of capture from both monitoring traps (unbaited and lactone-baited yellow sticky traps). We found out that one orchard would have initiated a treatment based on the conventional unbaited traps. Based on the captures from the lactone-baited traps, 11 orchards have observed three consecutive fly captures and would have initiated treatment. Discussion Monitoring traps play a crucial role in fruit protection by warning producers of the presence of pests. They allow for a more sustainable crop protection strategy, especially when the pest population is detected at its earlier stage of development. Since the 1970s, insect monitoring traps have improved through use of food attractants and pheromones (Gregg et al. 2018). However, they are mainly limited to Lepidopterans (Suckling 2015). Monitoring of R. completa would also benefit from a monitoring strategy that would allow earlier detection, since early phytosanitary treatments reduce final pest damages. To date, no species-specific attractant (e.g., sex pheromones) was identified in R. completa. And yet, male R. completa typically select a fruit that they defend against other males and attempt to mate with females that land on the walnut (Bush 1966). The attraction of a female would be favored by the emission of male sex pheromones that would attract females both to a sex partner and an oviposition site. In this study, two lactones were identified from newly emerged R. completa males and not from females. Associated with yellow sticky traps, they noticeably increased the attraction of flies during our field assay. Whether these two lactones are involved in the sexual communication of R. completa remains uncertain. Unfortunately, the number of captures was so important that we were not able to identify their gender, and make sure that females only were attracted to male-produced lactones. Some lactones have already been identified in tephritid species, including different species of Anastrepha (Battiste et al. 1983). Further studies are required to shed light on their biological function. Both molecules have one chiral center, resulting in their representing as R or S enantiomers. Additional volatile collection, followed by chiral separation, is needed to better characterize their natural structure and determine whether the enantiomeric ratio changes over the lifespan of the flies. Such conformations contribute to odor recognition by insects (Rowley et al. 2017). Secondly, electrophysiological assays could determine whether females’ olfactory apparatus perceives these lactones. Thirdly, behavioral assays could evaluate their ability to attract females exclusively and to lead to copulation. Whether these molecules are released throughout the entire adult stage must also be tested. Finally, these lactones might also act synergistically with fruit kairomones, which would enhance the accuracy of this cue for a female to locate a male (Sarles et al. 2015, 2017). A complete identification of a sex pheromone in R. completa would open the way to other semiochemical-based management strategies, such as mating disruption (Cardé and Haynes 2004; Howse et al. 1998). From our field assay, we conclude that lactone-baited sticky traps are more efficient that the ammonium acetate-baited traps (Decis). Even if ammonium acetate is a potent food attractant, a study conducted in North American showed that ammonium carbonate could have stronger attractive properties than ammonium acetate (Van Steenwyk et al. 2014). To complete the present study, field assays comparing lactone-baited traps with ammonium carbonate-baited traps could be conducted. However, if both lactones are identified as sex pheromone for R. completa, they would have the advantage of being much more specific than any food attractant. As previously mentioned, our field results demonstrate that lactone-baited yellow sticky traps were more efficient in trapping R. completa during the entire fruit season. For each monitoring week, we observed higher average numbers of flies captured by the yellow sticky traps baited with lactones than by non-baited yellow sticky traps. Furthermore, addition of lactones to yellow traps allows early detection of flies (compared to non-baited traps), at the beginning of the season. Early detection is particularly important, because 1) three consecutive capture initiate phytosanitary treatment and 2) early treatments lead to lower fruit damage levels (Allwood 1996). These results are promising for further enhancement of the monitoring method, allowing a better planning of phytosanitary treatments. However, one should evaluate the cost associated with the production of both lactones (in a natural chiral conformation). The potential of sex pheromones as a component of integrated pest management strategies has already been demonstrated, especially in Lepidopterans. In French walnut orchards, sex pheromones are currently used to monitor another walnut pest, Cydia pomonella (Liu et al. 2016). Monitoring traps targeting both pest species (C. pomonella and R. completa) would be more practical and economical than traps for single species (Baroffio et al. 2018), since both species have overlapping distributions. Acknowledgments Landry Sarles was granted by a Fond National de la Recherche Scientifique-FRIA grant (Formation à la Recherche dans l’Industrie et dans l’Agriculture). The present paper is dedicated to the memory of István Markó, who could not read the final published version of this manuscript. References Cited Allwood , A. J . 1996 . Biology and ecology: prerequisites for understanding and managing fruit flies (Diptera: Tephritidae) , pp. 95–101. In Allwood , A. J. , Drew , R. A. I ., (eds.), Management of Fruit Flies in the Pacific, A regional symposium , October 28–31, 1996, Nadi, Fiji . Google Preview WorldCat COPAC Barić , B. , I. Pajač Živković , D. Šubić , M. Šubić , E. Voigt , and M. Tóth . 2015 . Rhagoletis completa (Diptera; Tephritidae) distribution, flight dynamics and influence on walnut kernel quality in the continental Croatia . Poljoprivreda . 21 : 53 – 58 . Google Scholar Crossref Search ADS WorldCat Baroffio , C. A. , L. Sigsgaard , E. J. Ahrenfeldt , A. K. Borg-Karlson , S. A. Bruun , J. V. Cross , M. T. Fountain , D. Hall , R. Mozuraitis , B. Ralle , et al. 2018 . Combining plant volatiles and pheromones to catch two insect pests in the same trap: examples from two berry crops . Crop Prot . 109 : 1 – 8 . Google Scholar Crossref Search ADS WorldCat Battiste , M. A. , L. Strekowski , D. P. Vanderbilt , M. Visnick , and R. W. King . 1983 . Anastrephin and epianastrephin, novel lactone components isolated from the sex pheromone blend of male Caribbean and Mexican fruit flies . Tetrahedron Lett . 24 : 2611 – 2614 . Google Scholar Crossref Search ADS WorldCat Boyce , A. M . 1934 . Bionomics of the Walnut husk fly, Rhagoletis completa . Hilgardia . 8 : 363 – 579 . Google Scholar Crossref Search ADS WorldCat Bush , G. L . 1966 . The taxonomy, cytology, and evolution of the genus Rhagoletis in North America (Diptera, Tephritidae) . Bull. Museum Comp. Zool . 134 : 431 – 562 . WorldCat Cardé , R. T. , and K. F. Haynes . 2004 . Structure of the pheromone communication channel in moths , pp. 283 – 332 . In Cardé , R. T. , Miller , J. G . (eds.), Advances in Insect Chemical Ecology . Cambridge University Press, University of California , Riverside . Google Preview WorldCat COPAC Censier , F. , S. Heuskin , G. San Martin , Y. Gomez , F. Michels , M-L. Fauconnier , M. De Proft , G. C. Lognay , and B. Bodson . 2016 . A pheromone trap monitoring system for the saddle gall midge, Haplodiplosis marginata (von Roser) (Diptera: Cecidomyiidae) . Crop Prot . 80 : 1 – 6 . Google Scholar Crossref Search ADS WorldCat Duso , C. , and G. D. Lago . 2006 . Life cycle, phenology and economic importance of the walnut husk fly Rhagoletis completa Cresson (Diptera: Tephritidae) in northern Italy . Ann. la Société Entomol. Fr . 42 : 245 – 254 . Google Scholar Crossref Search ADS WorldCat EPPO . 2013 . EPPO. PQR Database . http://www.eppo.org. Gregg , P. C. , A. P. Del Socorro , and P. J. Landolt . 2018 . Advances in attract-and-kill for agricultural pests: beyond pheromones . Annu. Rev. Entomol . 63 : 453 – 470 . Google Scholar Crossref Search ADS PubMed WorldCat Heuskin , S. , B. Godin , P. Leroy , Q. Capella , J. P. Wathelet , F. Verheggen , E. Haubruge , and G. Lognay . 2009 . Fast gas chromatography characterisation of purified semiochemicals from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae) . J. Chromatogr. A . 1216 : 2768 – 2775 . Google Scholar Crossref Search ADS PubMed WorldCat Howse , P. , I. Stevens , and O. Jones . 1998 . Insect pheromones and their use in pest management . Chapman and Hall , London, United Kingdom . Google Preview WorldCat COPAC Levi-Zada , A. , D. Nestel , D. Fefer , E. Nemni-Lavy , I. Deloya-Kahane , and M. David . 2012 . Analyzing diurnal and age-related pheromone emission of the olive fruit fly, Bactrocera oleae by sequential SPME-GCMS analysis . J. Chem. Ecol . 38 : 1036 – 1041 . Google Scholar Crossref Search ADS PubMed WorldCat Light , D. M . 2016 . Control and monitoring of codling moth (Lepidoptera: Tortricidae) in walnut orchards treated with novel high-load, low-density “Meso” dispensers of sex pheromone and pear ester . Environ. Entomol . 45 : 700 – 707 . Google Scholar Crossref Search ADS WorldCat Liu , W. , J. Xu , and R. Zhang . 2016 . The optimal sex pheromone release rate for trapping the codling moth Cydia pomonella (Lepidoptera: Tortricidae) in the field . Sci. Rep . 6 . WorldCat R Development CoreTeam . 2005 . R: a language and environment for statistical computing . R Foundation for Statistical Computing , Vienna, Austria . http://www.R-project.org/. Google Preview WorldCat COPAC Rowley , C. , T. W. Pope , A. Cherrill , S. R. Leather , G. M. Fernández-Grandon , and D. R. Hall . 2017 . Development and optimisation of a sex pheromone lure for monitoring populations of saddle gall midge, Haplodiplosis marginata . Entomol. Exp. Appl . 163 : 82 – 92 . Google Scholar Crossref Search ADS WorldCat Samietz , J. , R. Baur , and Y. Hillbur . 2012 . Potential of synthetic sex pheromone blend for mating disruption of the swede midge, Contarinia nasturtii . J. Chem. Ecol . 38 : 1171 – 1177 . Google Scholar Crossref Search ADS PubMed WorldCat Sarles , L. , A. Verhaeghe , F. Francis , and F. J. Verheggen . 2015 . Semiochemicals of Rhagoletis fruit flies: potential for integrated pest management . Crop Prot . 78 : 114 – 118 . Google Scholar Crossref Search ADS WorldCat Sarles , L. , A. Boullis , B. Fassotte , G. Lognay , A. Verhaeghe , F. Francis , and F. J. Verheggen . 2017 . Identification of walnut husk (Juglans regia L.) volatiles and the behavioural response of the invasive Walnut Husk Fly, Rhagoletis completa Cresson . Pest Manag. Sci . 73 : 2100 – 2104 . Google Scholar Crossref Search ADS PubMed WorldCat Suckling , D. M . 2015 . Sex pheromones and semiochemicals offer an elegant future for pest management and biosecurity . Acta Hortic . 1105 : 275 – 281 . WorldCat Van Steenwyk , R. A. , L. M. Novotny , L. Thayer , G. B. Weiss , W. W. Coates , A. Verhaeghe , J. A. Grant , and J. K. Hasey . 2014 . Evaluation of monitoring techniques for walnut husk fly . Acta Hortic . 1050 : 263 – 270 . Google Scholar Crossref Search ADS WorldCat Verheggen , F. J. , A. Verhaeghe , P. Giordanengo , X. Tassus , and A. Escobar-Gutiérrez . 2017 . Walnut husk fly, Rhagoletis completa (Diptera : Tephritidae), invades Europe: invasion potential and control strategies . Appl. Entomol. Zool . 52 : 1 – 7 . Google Scholar Crossref Search ADS WorldCat © The Author(s) 2018. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
TI - Improving the Monitoring of the Walnut Husk Fly (Diptera: Tephritidae) Using Male-Produced Lactones
JO - Journal of Economic Entomology
DO - 10.1093/jee/toy169
DA - 2018-09-26
UR - https://www.deepdyve.com/lp/oxford-university-press/improving-the-monitoring-of-the-walnut-husk-fly-diptera-tephritidae-hhlliKZEWR
SP - 2032
VL - 111
IS - 5
DP - DeepDyve
ER -