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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.

Temperature-dependent fecundity and survival data was integrated into a matrix population model to describe relative Drosophila suzukii Matsumura (Diptera: Drosophilidae) population increase and age structure based on environmental conditions. This novel modification of the classic Leslie matrix population model is presented as a way to examine how insect populations interact with the environment, and has application as a predictor of population density. For D. suzukii, we examined model implications for pest pressure on crops. As case studies, we examined model predictions in three small fruit production regions in the United States (US) and one in Italy. These production regions have distinctly different climates. In general, patterns of adult D. suzukii trap activity broadly mimicked seasonal population levels predicted by the model using only temperature data. Age structure of estimated populations suggest that trap and fruit infestation data are of limited value and are insufficient for model validation. Thus, we suggest alternative experiments for validation. The model is advantageous in that it provides stage-specific population estimation, which can potentially guide management strategies and provide unique opportunities to simulate stage-specific management effects such as insecticide applications or the effect of biological control on a specific life-stage. The two factors that drive initiation of the model are suitable temperatures (biofix) and availability of a suitable host medium (fruit). Although there are many factors affecting population dynamics of D. suzukii in the field, temperature-dependent survival and reproduction are believed to be the main drivers for D. suzukii populations.

The olive fruit fly was first detected in Los Angeles in 1998 and in all the olive-growing regions of California soon after. Following its initial detection, UC researchers and Cooperative Extension farm advisors, county agricultural commissioners and the California Department of Food and Agriculture Pest Detection and Emergency Project established a statewide monitoring program to determine the extent of the olive fruit fly’s occurrence, track its seasonal biology and evaluate monitoring tools. Fly populations and infestations can reach high levels throughout California but tend to be lower in the San Joaquin Valley. Trap captures typically exhibit a bimodal distribution with peaks in the spring and fall. Olive infestation is related to fly densities, climate and fruit size. Gravid, mated females vary in density throughout the year but are present at some level year-round. The data is being used to develop models that will better predict when the adults are active and olives are at risk.

1. Dead arthropods, entrapped by trichomes on plant surfaces, are an underappreciated form of plant‐provided food. Specialist predatory arthropods able to manoeuvre on plants covered in trichomes facultatively scavenge on the alternative food resource, increasing their abundance and reducing plant damage by herbivores. 2. This protective mutualism dependent on arthropod carrion has been demonstrated in several plant species, but the mechanisms driving the increase in predator abundance have not been identified. Through a series of greenhouse and laboratory experiments, the effect of arthropod carrion on predator behaviour was assessed. 3. The predator Jalysus wickhami preferred Nicotiana tabacum plants augmented with arthropod carrion, spending significantly more time and laying more eggs on those plants than plants without arthropod carrion. 4. Under low J. wickhami densities, arthropod carrion did not reduce egg cannibalism by adults. Under high densities, egg cannibalism by J. wickhami adults was reduced in the presence of arthropod carrion, but cannibalism by fifth instars was not. 5. Arthropod carrion may be utilised by a wide range of predatory arthropods that facultatively scavenge, and this research demonstrates its potential for influencing arthropod–plant and arthropod–arthropod interactions. [ABSTRACT FROM AUTHOR]

Two invasive drosophilids, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) and Zaprionus indianus (Gupta) (Diptera: Drosophilidae) are expanding their geographic distribution and cohabiting grape production in the Mid-Atlantic. The ecological and economic impact of these two species within vineyards is currently unknown. Zaprionus indianus was presumably not capable of ovipositing directly into grapes because they lack a serrated ovipositor and may use D. suzukii oviposition punctures for depositing their own eggs. Therefore, an interspecific larval competition assay was performed at varying larval densities using commercial medium and four commonly grown wine grapes in Virginia to investigate the impact Z. indianus larvae may have on the mortality and developmental parameters of D. suzukii larvae. Zaprionus indianus did not affect D. suzukii mortality or development parameters even at high interspecific densities when reared in commercial medium, but it did cause higher D. suzukii mortality within grapes. Mortality was also influenced by the variety of grape in which the larvae were reared, with smaller grapes having the highest D. suzukii mortality. Presence of Z. indianus also increased development time to pupariation and adult emergence for most interspecific competition levels compared with the intraspecific D. suzukii controls. Pupal volume was marginally affected at the highest interspecific larval densities. This laboratory study suggests that competition from Z. indianus and grape variety can limit D. suzukii numbers, and the implications on D. suzukii pest management be further verified in the field. [ABSTRACT FROM AUTHOR]