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Drosophila suzukii, or spotted-wing drosophila, is now an established pest in many parts of the world, causing significant damage to numerous fruit crop industries. Native to East Asia, D. suzukii infestations started in the United States a decade ago, occupying a wide range of climates. To better understand invasion ecology of this pest, knowledge of past migration events, population structure, and genetic diversity is needed. In this study, we sequenced whole genomes of 237 individual flies collected across the continental United States, as well as several sites in Europe, Brazil, and Asia, to identify and analyze hundreds of thousands of genetic markers. We observed strong population structure between Western and Eastern US populations, but no evidence of any population structure between different latitudes within the continental United States, suggesting that there are no broad-scale adaptations occurring in response to differences in winter climates. We detect admixture from Hawaii to the Western United States and from the Eastern United States to Europe, in agreement with previously identified introduction routes inferred from microsatellite analysis. We also detect potential signals of admixture from the Western United States back to Asia, which could have important implications for shipping and quarantine policies for exported agriculture. We anticipate this large genomic dataset will spur future research into the genomic adaptations underlying D. suzukii pest activity and development of novel control methods for this agricultural pest., (© The Author(s) 2021. Published by Oxford University Press on behalf of Genetics Society of America.)

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) also known as spotted-wing drosophila (SWD), is a pest native to Southeast Asia. In the last few decades, the pest has expanded its range to affect all major European and American fruit production regions. SWD is a highly adaptive insect that is able to disperse, survive, and flourish under a range of environmental conditions. Infestation by SWD generates both direct and indirect economic impacts through yield losses, shorter shelf life of infested fruit, and increased production costs. Fresh markets, frozen berries, and fruit export programs have been impacted by the pest due to zero tolerance for fruit infestation. As SWD control programs rely heavily on insecticides, exceedance of maximum residue levels (MRLs) has also resulted in crop rejections. The economic impact of SWD has been particularly severe for organic operations, mainly due to the limited availability of effective insecticides. Integrated pest management (IPM) of SWD could significantly reduce chemical inputs but would require substantial changes to horticultural management practices. This review evaluates the most promising methods studied as part of an IPM strategy against SWD across the world. For each of the considered techniques, the effectiveness, impact, sustainability, and stage of development are discussed., (© The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The invasive spotted-wing drosophila, Drosophila suzukii (Matsumura), is a major pest of soft-skinned fruits. Since its introduction into North America and Europe, significant progress has been made in understanding the volatile cues used by this fly during food, oviposition site, and mate finding. Despite this progress, commercially available lures are non-selective. Here, we tested two Hanseniaspora uvarum (Niehaus) yeast compounds (isoamyl acetate and isobutyl acetate) and a leaf compound β-cyclocitral alone and in combination with a blend of four fermentation compounds ('Fermentation lure': acetic acid, ethanol, methionol, and acetoin) to improve D. suzukii attraction and selectivity. In laboratory assays, males and females were attracted to all seven individual compounds, although in electrophysiological assays, their antennae exhibited a dose-dependent response to only four of these compounds. In two-choice cage studies, the Fermentation lure was more attractive to D. suzukii than water controls, whereas β-cyclocitral and the mixture of isoamyl acetate and isobutyl acetate were not attractive in this larger-cage study. Moreover, adding the two-component H. uvarum compound blend to the Fermentation lure reduced D. suzukii attraction to the Fermentation blend. When these experiments were repeated in blueberry, raspberry, blackberry, and cherry orchards across several states in the United States over 2 yr, similar outcomes were observed: β-cyclocitral or the mixture of the H. uvarum blend did not improve the attractiveness of the Fermentation lure or its selectivity. This study demonstrates that cues from different sources may interfere with each other and reduce D. suzukii attraction to otherwise attractive odor combinations., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Invasive insect pests can be challenging to manage because their recent arrival provides limited information on which to build predictive population models. The magnitude and timing of activity by the invasive vinegar fly, Drosophila suzukii, in crop fields has been unpredictable due to its recent arrival in many new regions of the world and changes in methods for its detection. Using 7 yr of consistent trapping of adults at four blueberry farms in Michigan, United States, we modeled the temporal and environmental factors influencing D. suzukii activity. We found that this pest established high levels within 2 yr of being detected, with peak fly activity continuing to increase. Fly activity timing and abundance were predicted by the annual number of days below 0°C, the number of winter and spring days above 10°C, and by the fly activity in the preceding year, providing support for overwintering in our region. We monitored larval infestation for 4 yr at these same sites and found a moderate positive correlation between larvae in fruit and adults in traps. Finally, we developed a generalized additive model to predict D. suzukii fly capture throughout the season based on relevant environmental factors and examined the relative timing and magnitude of activity under varying winter and spring temperature conditions. Our results suggest that D. suzukii activity is predictable and that environmental conditions can be used in temperate regions to provide regional risk warnings as a component of strategies to manage this invasive insect pest., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

With a high surface to volume ratio, small organisms must carefully regulate their internal water status. Spotted-wing drosophila, Drosophila suzukii (Matsumura), is an invasive frugivorous insect distributed across a wide range of geographical regions that can have periods of dry and hot weather, suggesting that this species has strategies to avoid stressful environments and reduce water loss. It also survives winter as an adult fly, indicating that it has adaptations to the low air humidity of this season. To determine the importance of water stress to D. suzukii, we studied their survival in environments of low humidity, which was manipulated using Drierite, and their survival and water loss in response to desiccation. Survival of both sexes was lower in drier conditions, and while female winter morph D. suzukii had higher mortality early on, remaining flies were able to survive longer in the drier conditions than the summer morphs. A bioassay method was adapted from Enjin et al. (2016) using 48-well plates to videotape the location of flies and quantify their behavioral responses to humidity. Male and female D. suzukii avoided dry conditions within the bioassay system, but only when there was at least 25% differential between humidity extremes. This response was observed for both summer and winter morphs of D. suzukii and our results provide guidance for attempts to manipulate crop environments to reduce the economic impact of this pest., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is currently a major pest management challenge in berry and cherry production. This species has a winter morph phenotype with longer wings and increased melanization associated with survival in colder conditions. Measurements of wing morphology in Michigan D. suzukii collected during 2016 and 2017 showed that induction of this morph began in September and increased into December, correlated with decreasing temperature and day length. Importantly, we found that wing length increases along a continuous scale and there is overlap between the two morph types. We tested whether temperature or photoperiod elicited this phenotypic change using a factorial design with each preadult lifestage held at 10 or 25°C and 16:8 or 8:16 L:D. Our results support temperature as the main driver of transition to the winter morph for all immature stages. Comparing the reproductive capacity of winter morph flies in cold conditions and when previously acclimated to warm conditions, flies with the acclimation experience laid comparable numbers of eggs as the summer morphs at 25°C, indicating that winter morphs can reproduce after surviving cold periods. These results highlight the ability of D. suzukii to adapt to changing temperature conditions, allowing it to survive cold and also exploit warmer periods to build populations when conditions allow., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America.)

Background: Spotted wing Drosophila is an invasive pest of fruit crops in most production regions globally, and insecticides are commonly used for its control. The biology of this pest combined with repeated pesticide exposure increases the risk of resistance to insecticides. We tested malathion, methomyl, spinetoram, spinosad, and zeta-cypermethrin against multiple colonies from each state using a contact bioassay method to determine diagnostic doses for assessment of insecticide susceptibility in this species. These were used to test populations collected in Michigan and Georgia, USA., Results: Concentrations required to reach 50% (LC 50 ) and 90% mortality (LC 90 ) were calculated for the tested populations, and male mortality consistently occurred at lower concentrations than female mortality. Fly mortality did not vary significantly among populations collected from unmanaged, organic, and conventional fields. Similar results were found using the diagnostic concentrations applied to glass jars., Conclusions: Using this method, samples of D. suzukii that are freshly caught or reared from fruit can be tested within 1 day for their mortality in response to discriminating doses of five key insecticides. This method can be used to inform proactive resistance management strategies within integrated pest management programs. © 2019 Society of Chemical Industry., (© 2019 Society of Chemical Industry.)

Drosophila suzukii Matsumura is an invasive species affecting berry crops and cherries throughout North America, South America, and Europe. Previous research suggests that in temperate climates, the overwintering success of D. suzukii is likely dependent on access to food, shelter, and adequate cold hardening. We performed a multi-state study under field conditions for two winters to determine whether D. suzukii sex, phenotype (summer-morphotype, winter-morphotype), and life stage (adults, pupae) affected survival over time while recording naturally-occurring spatial and temporal variation in temperature. Access to food was provided and the flies were buried under leaf litter. Baited traps were deployed to determine whether local populations of D. suzukii were active throughout the winter season. The duration of exposure, mean daily temperature, and cumulative time below freezing significantly affected survival. Below freezing, D. suzukii survival was significantly reduced, particularly in northern locations. In contrast, we observed sustained survival up to 10 wk in southern locations among adults and pupae. Biotic factors also significantly affected survival outcomes: female survival was greater than male survival, winter-morphotype survival was greater than summer-morphotype survival, and adult survival was greater than pupal survival. In the north, wild D. suzukii were captured only in early winter, while in the south they were found throughout the winter. These data suggest that although adult D. suzukii may overwinter in sheltered microclimates, this ability may be limited in regions where the ground temperature, or site of overwintering, falls below freezing for extended durations., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a devastating global pest of berry crops and cherries. Little is understood about its biology during the winter in northern temperate regions, including potential resources that it may utilize during this period. In this study, olfactory and behavioral responses of female D. suzukii to six volatiles (methionol, acetic acid, linalool, bornyl acetate, isoamyl acetate, and geosmin) were evaluated separately for electroantennogram (EAG) and behavioral assays between summer and winter morphs. Results of EAG indicated that isoamyl acetate, acetic acid, and geosmin elicited significantly higher olfactory responses from the antennae of female summer morph D. suzukii compared with those of female winter morph D. suzukii. Winter morph D. suzukii showed reduced antennal response to the volatiles overall. Geosmin and bornyl acetate elicited significantly different behavioral responses from the two morphs in no-choice laboratory behavioral assays. T-maze behavioral assays with geosmin further revealed that summer morphs had a significant aversion, while winter morphs showed no significant aversion to geosmin. Overall, we demonstrate that responses of the two seasonally induced morphs to environmental stimuli are different, and future studies are justified to further understand how these physiological and behavioral differences may contribute to improved pest management of D. suzukii.

Background: The invasive drosophilid pest, Drosophila suzukii Matsumura, is affecting berry production in most fruit-producing regions of the world. Chemical control is the dominant management approach, creating concern for insecticide resistance in this pest. We compared the insecticide susceptibility of D. suzukii populations collected from conventional, organic or insecticide-free blueberry sites., Results: The sensitivity of D. suzukii to malathion and spinetoram declined slightly across the 3 years of monitoring, whereas it was more consistent for methomyl and zeta-cypermethrin. The sensitivity of D. suzukii to all four insecticides (LC 50 and LC 90 values) did not differ significantly among the blueberry fields using different management practices., Conclusions: The baseline sensitivity of D. suzukii has been characterized, allowing future comparisons if field failures of chemical control are reported. The concentration achieving high control indicates that effective levels of control can still be achieved with field rates of these four insecticides. However, declining susceptibility of some populations of D. suzukii to some key insecticides highlights the need for resistance monitoring. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

Spotted wing Drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), is an invasive vinegar fly that has become a primary direct pest of berry crops worldwide. We conducted 2 yr of behavioral studies in blueberry plantings to determine how fly activity varied throughout the day. Observations of diurnal activity of adult D. suzukii found the greatest activity in the morning hours between 0600 and 0800 hours, when the majority of flies were on the berries. Flies were also active in the evening mainly between 1800 and 2000 hours; however, this trend was more prominent in 2015, which had cooler and more humid evenings. Experiments examining the effect of irrigation on D. suzukii behavior showed that flies remained active during and after irrigation. The effect of insecticide treatments alone and in combination with irrigation revealed that treatment with spinosad had limited effects on the number of flies per bush, whereas spinetoram reduced the number flying and on the bushes in some cases. Zeta-cypermethrin caused longer and more consistent reduction in D. suzukii flying and on bushes. In all treatments, we observed surviving flies flying near and on treated bushes, indicating that these insecticides do not completely deter fly activity. Irrigation did not influence the effects of zeta-cypermethrin on fly behavior during daily observations up to 3 d after application. Our results highlight that the diurnal patterns of activity of D. suzukii on host plants are flexible and are relatively unaffected by irrigation or insecticide applications., (© The Author 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Drosophila suzukii Matsumara, also referred to as the spotted wing drosophila, has recently expanded its global range with significant consequences for its primary host crops: blueberries, blackberries, raspberries, cherries, and strawberries. D. suzukii populations can increase quickly, and their infestation is difficult to predict and prevent. The development of effective tools to detect D. suzukii presence in new areas, to time the beginning of activity within a crop, to track seasonal activity patterns, and to gauge the effectiveness of management efforts has been a key research goal. We compared the efficiency, selectivity, and relationship to fruit infestation of a range of commonly used homemade baits and a synthetic formulated lure across a wide range of environments in 10 locations throughout the United States. Several homemade baits were more efficient than apple cider vinegar, a commonly used standard, and a commercially formulated lure was, in some configurations and environments, comparable with the most effective homemade attractant as well as potentially more selective. All alternative attractants also captured flies between 1 and 2 wk earlier than apple cider vinegar, and detected the presence of D. suzukii prior to the development of fruit infestation. Over half the Drosophila spp. flies captured in traps baited with any of the attractants were not D. suzukii, which may complicate their adoption by nonexpert users. The alternative D. suzukii attractants tested are improvement on apple cider vinegar and may be useful in the development of future synthetic lures., (© The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Drosophila suzukii (Matsumura), an invasive pest of small and stone fruits, has been recently detected in 39 states of the United States, Canada, Mexico, and Europe. This pest attacks ripening fruit, causing economic losses including increased management costs and crop rejection. Ongoing research aims to improve the efficacy of monitoring traps. Studies were conducted to evaluate how physical trap features affect captures of D. suzukii. We evaluated five colors, two bait surface areas, and a top and side position for the fly entry point. Studies were conducted at 16 sites spanning seven states and provinces of North America and nine crop types. Apple cider vinegar was the standard bait in all trap types. In the overall analysis, yellow-colored traps caught significantly more flies than clear, white, and black traps; and red traps caught more than clear traps. Results by color may be influenced by crop type. Overall, the trap with a greater bait surface area caught slightly more D. suzukii than the trap with smaller area (90 vs. 40 cm(2)). Overall, the two traps with a side-mesh entry, with or without a protective rain tent, caught more D. suzukii than the trap with a top-mesh entry and tent.

Drosophila suzukii Matsumura (Diptera: Drosophilidae), a recent invasive pest of small and stone fruits, has been detected in more than half of the U.S. states, and in Canada, Mexico, and Europe. Upon discovery, several different trap designs were recommended for monitoring. This study compared the trap designs across seven states/provinces in North America and nine crop types. Between May and November 2011, we compared a clear cup with 10 side holes (clear); a commercial trap with two side holes (commercial); a Rubbermaid container with mesh lid and rain tent (Haviland), and with 10 side holes and no tent (modified Haviland); a red cup with 10 side holes (red); and a white container with mesh lid and rain tent (Van Steenwyk). Although fly catches among traps varied per site, overall, the Haviland trap caught the most D. suzukii, followed by the red, Van Steenwyk, and clear trap. The modified Haviland and commercial trap had low captures. Among five crop types in Oregon, a clear cup with mesh sides (Dreves) also was tested and caught the most flies. Traps with greater entry areas, found in mesh traps, caught more flies than traps with smaller entry areas. In terms of sensitivity and selectivity, traps that caught more flies likewise caught flies earlier, and all traps caught 26-31% D. suzukii out of the total Drosophila captured. Future trap improvements should incorporate more entry points and focus on selective baits to improve efficiency and selectivity with regard to the seasonal behavior of D. suzukii.

Background: Drosophila suzukii was first found in Oregon in August 2009. The threat of this pest to regional small and stone fruit production industries led to investigations on its overwintering capabilities in fruit-growing regions in the Pacific Northwest. Knowledge of its cold tolerance will help in the development of computer models to forecast seasonal population growth and decline., Results: Of 1500 adults or pupae, 22 (1.4%) individuals survived the 84 day experimental chilling period. Most (86%) of the survivors were subjected to 10 °C temperature treatments. Survival decreased significantly at lower temperature treatments. Freezing temporarily increased the mortality rate but did not significantly affect overall mortality over the trial period. Flies that emerged from pupae are estimated to survive for up to 103-105 days at 10 °C and for shorter periods at lower temperatures. Field trapping in five fruit production areas has demonstrated overwintering survival in California and Oregon, but lower survival is predicted in Eastern Washington and Michigan., Conclusion: The experiments reported here indicate that long-term survival of D. suzukii is unlikely at temperatures below 10 °C. Field data from five climatic regions indicated extended low initial D. suzukii field presence in 2010 in all regions except California, where field presence was recorded earlier., (Copyright © 2011 Society of Chemical Industry.)