Genome divergence and reproductive incompatibility among populations of Ganaspis near brasiliensis.

During the last decade, the spotted-wing drosophila, Drosophila suzukii, has spread from eastern Asia to the Americas, Europe, and Africa. This fly attacks many species of cultivated and wild fruits with soft, thin skins, where its serrated ovipositor allows it to lay eggs in undamaged fruit. Parasitoids from the native range of D. suzukii may provide sustainable management of this polyphagous pest. Among these parasitoids, host-specificity testing has revealed a lineage of Ganaspis near brasiliensis, referred to in this paper as G1, that appears to be a cryptic species more host-specific to D. suzukii than other parasitoids. Differentiation among cryptic species is critical for introduction and subsequent evaluation of their impact on D. suzukii. Here we present results on divergence in genomic sequences and architecture and reproductive isolation between lineages of Ganaspis near brasiliensis that appear to be cryptic species. We studied five populations, two from China, two from Japan, and one from Canada, identified as the G1 versus G3 lineages based on differences in cytochrome oxidase l sequences. We assembled and annotated the genomes of these populations and analyzed divergences in sequence and genome architecture between them. We also report results from crosses to test reproductive compatibility between the G3 lineage from China and the G1 lineage from Japan. The combined results on sequence divergence, differences in genome architectures, ortholog divergence, reproductive incompatibility, differences in host ranges and microhabitat preferences, and differences in morphology show that these lineages are different species. Thus, the decision to evaluate the lineages separately and only import and introduce the more host-specific lineage to North America and Europe was appropriate.

Landscape-scale spatiotemporal dynamics of Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) populations: implications for spatially-based pest management.

BACKGROUND: Brown marmorated stink bug (BMSB), Halyomorpha halys (Stål), is an invasive and severe pest of specialty and row crops. A 2-year field study conducted in four Mid-Atlantic states in the USA characterized the spatial and temporal dynamics of BMSB populations and its association with landscape elements in commercial agriculture settings. In each state, two 1 km2 sites included typical landscape elements (i.e., tree fruit orchards, annual field and vegetable crops, woodlands, and human-made structures). Twenty-seven georeferenced pheromone traps were deployed per site and the number of BMSB adults and nymphs captured was counted throughout the growing season. RESULTS: Findings from spatial analysis by distance indices, along with time-series maps of BMSB distribution, showed that BMSB exhibited significant spatial aggregation, and that its distribution was spatially consistent between years. Analyses with geographic information systems (GIS) revealed that BMSB 'hot spots' occurred in different landscape elements throughout each season. Most patches (i.e., clusters of significantly higher trap captures) were found near woodlands early in the season, near tree fruit orchards in summer, and on the border of annual field crops in autumn. Buffer analysis with GIS indicated that more BMSB adults were captured closer to woodlands compared with other landscape elements. CONCLUSION: Understanding the spatial and temporal movement and distribution of BMSB is critical to predicting their potential impact and ultimately devising strategies to mitigate this risk to vulnerable crops. The results of this study can be used to design streamlined, spatially-based areawide management of BMSB in heterogeneous and complex agricultural landscapes. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Accessing biological control genetic resources: the United States perspective.

The USA has been actively involved in classical biological control projects against invasive insect pests and weeds since 1888. Classical (importation) biological control relies upon natural enemies associated through coevolution with their target species at their geographic origin to also provide long-term, self-sustaining management where the pest/weed has become invasive. Biological control agents are a form of genetic resources and fall under the purview of the 1993 Convention on Biological Diversity (CBD) and its Nagoya Protocol (NP), which entered into force in 2014 to address equitable sharing of benefits arising from utilization of genetic resources. Safe and effective classical biological control agents have historically been shared among countries experiencing problems with invasive species. However, a feature of the Nagoya Protocol is that countries are expected to develop processes governing access to their genetic resources to ensure that the benefits are shared equitably-a concept referred to as "access and benefit sharing" (ABS). Although the USA is not party to the CBD nor the NP, US biological control programs are affected by these international agreements. Surveying, collecting, exporting and importing of natural enemies may be covered by new ABS regulatory processes. Challenges of ABS have arisen as various countries enact new regulations (or not) governing access to genetic resources, and the processes for gaining access and sharing the benefits from these resources have become increasingly complex. In the absence of an overarching national US policy, individual government agencies and institutions follow their own internal procedures. Biological control practitioners in the USA have been encouraged in recent years to observe best practices developed by the biological community for insect and weed biological control.

Assessing the host range of Anastatus orientalis, an egg parasitoid of spotted lanternfly (Lycorma delicatula) using Eastern U.S. non-target species.

The spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), an invasive planthopper discovered in Pennsylvania, U.S. in 2014, has spread to many surrounding states despite quarantines and control efforts, and further spread is anticipated. A classical (importation) biological control program would contribute to the long-term management of L. delicatula in the eastern U.S. In its native range of China, Anastatus orientalis (Hymenoptera: Eupelmidae), an egg parasitoid, causes significant mortality. Anastatus orientalis consists of multiple haplotypes that differ in important biological parameters. To delineate the physiological host range of A. orientalis Haplotype C, we completed no-choice and choice testing. No-choice testing of non-target eggs from 36 insect species spanning six orders and 18 families showed that physiologically this haplotype of A. orientalis can develop in a variety of host species eggs from the families Coreidae, Fulgoridae, Pentatomidae, and Saturniidae. Ten of the 16 species that were attacked in the no-choice tests were also attacked in the choice tests. The production of progeny on non-target egg masses was significantly lower than on the controls (L. delicatula egg masses run simultaneously) in the no-choice and choice tests. For the non-target species that were attacked and resulted in female wasp progeny, these females were able to produce their own progeny at the same rate as control females that were reared from the L. delicatula eggs. Larger host eggs corresponded to an increased female-biased sex ratio of the progeny, suggesting that gravid females select them for fertilized eggs. Results from these studies suggest that A. orientalis Haplotype C prefers to parasitize L. delicatula egg masses but is capable of developing in some non-target species.

Evaluating invasion risk and population dynamics of the brown marmorated stink bug across the contiguous United States.

BACKGROUND: Invasive species threaten the productivity and stability of natural and managed ecosystems. Predicting the spread of invaders, which can aid in early mitigation efforts, is a major challenge, especially in the face of climate change. While ecological niche models are effective tools to assess habitat suitability for invaders, such models have rarely been created for invasive pest species with rapidly expanding ranges. Here, we leveraged a national monitoring effort from 543 sites over 3 years to assess factors mediating the occurrence and abundance of brown marmorated stink bug (BMSB, Halyomorpha halys), an invasive insect pest that has readily established throughout much of the United States. RESULTS: We used maximum entropy models to estimate the suitable habitat of BMSB under several climate scenarios, and generalized boosted models to assess environmental factors that regulated BMSB abundance. Our models captured BMSB distribution and abundance with high accuracy, and predicted a 70% increase in suitable habitat under future climate scenarios. However, environmental factors that mediated the geographical distribution of BMSB were different from those driving abundance. While BMSB occurrence was most affected by winter precipitation and proximity to populated areas, BMSB abundance was influenced most strongly by evapotranspiration and solar photoperiod. CONCLUSION: Our results suggest that linking models of establishment (occurrence) and population dynamics (abundance) offers a more effective way to forecast the spread and impact of BMSB and other invasive species than simply occurrence-based models, allowing for targeted mitigation efforts. Implications of distribution shifts under climate change are discussed. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Methods for Rearing the Parasitoid Ganaspis brasiliensis, a Promising Biological Control Agent for the Invasive Drosophila suzukii.

Native to East Asia, the spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), has established widely in the Americas, Europe, and parts of Africa over the last decade, becoming a devastating pest of various soft-skinned fruits in its invaded regions. Biological control, especially by means of self-perpetuating and specialized parasitoids, is expected to be a viable option for sustainable area-wide management of this highly mobile and polyphagous pest. Ganaspis brasiliensis Ihering (Hymenoptera: Figitidae) is a larval parasitoid that is widely distributed in East Asia, and has been found to be one of the most effective parasitoids of D. suzukii. Following rigorous pre-introduction evaluations of its efficacy and potential non-target risks, one of the more host-specific genetic groups of this species (G1 G. brasiliensis) has been approved recently for introduction and field release in the United States and Italy. Another genetic group (G3 G. brasiliensis), which was also commonly found to attack D. suzukii in East Asia, may be considered for introduction in the near future. There is currently enormous interest in rearing G. brasiliensis for research or in mass-production for field release against D. suzukii. This protocol and associated video article describe effective rearing methods for this parasitoid, both on a small scale for research and a large scale for mass-production and field release. These methods may benefit further long-term research and use of this Asian-native parasitoid as a promising biological control agent for this global invasive pest.

A Coordinated Sampling and Identification Methodology for Larval Parasitoids of Spotted-Wing Drosophila.

We provide recommendations for sampling and identification of introduced larval parasitoids of spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). These parasitoids are either under consideration for importation (aka classical) biological control introductions, or their adventive (presumed to have been accidentally introduced) populations have recently been discovered in North America and Europe. Within the context of the ecology of D. suzukii and its parasitoids, we discuss advantages and disadvantages of estimating larval parasitism levels using different methods, including naturally collected fruit samples and sentinel baits. For most situations, we recommend repeated sampling of naturally occurring fruit rather than using sentinel baits to monitor seasonal dynamics of host plant-Drosophila-parasitoid associations. We describe how to separate Drosophilidae puparia from host fruit material in order to accurately estimate parasitism levels and establish host-parasitoid associations. We provide instructions for identification of emerging parasitoids and include a key to the common families of parasitoids of D. suzukii. We anticipate that the guidelines for methodology and interpretation of results that we provide here will form the basis for a large, multi-research team sampling effort in the coming years to characterize the biological control and nontarget impacts of accidentally and intentionally introduced larval parasitoids of D. suzukii in several regions of the world.

Drosophila suzukii (Diptera: Drosophilidae): A Decade of Research Towards a Sustainable Integrated Pest Management Program.

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.

Preempting the Arrival of the Brown Marmorated Stink Bug, Halyomorpha halys: Biological Control Options for Australia.

The brown marmorated stink bug Halyomorphahalys (Stål) (Hemiptera: Pentatomidae) is native to Northeast Asia, but has become a serious invasive species in North America and Europe, causing major damage to crops. While it has not established itself in Australia, it has been intercepted at the border several times, indicating that future incursions and establishment are a case of when, not if. Biological control is one of the few control options for this species and will be important for managing H.halys should it become established in Australia. Prioritizing species that could be used as biological control agents would ensure Australia is prepared. This study summarizes the literature on natural enemies of H. halys in its native and invaded ranges and prioritizes potential biological control agents of H.halys that could be used in Australia. Two egg parasitoid species were identified: Trissolcusjaponicus (Ashmead) and Trissolcusmitsukurii (Ashmead) (Hymenoptera: Scelionidae). Future efforts to develop biological control should focus on T. mitsukurii, as it is already present in Australia. However, little is known about this species and further work is required to: (1) assess its potential effectiveness in parasitizing H. halys, (2) determine its current distribution and (3) host range in Australia.

Modelling the Potential Geographic Distribution of Two Trissolcus Species for the Brown Marmorated Stink Bug, Halyomorpha halys.

The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is native to northeast Asia. It was accidentally introduced to Europe and North America, where it has become a key pest, feeding on many important crops. Previous eco-climatic niche modelling indicates that H. halys could expand its distribution vastly, and numerous border interceptions of this pest in many countries, including Australia and New Zealand, indicate that it would be prudent to prepare for its eventual arrival. Similar niche modelling was used to assess the potential distribution of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), the key parasitoid of H. halys in China. Trissolcus mitsukurii (Ashmead) is one of the main parasitoids of H. halys in Japan. It is known to have existed in Australia since the early 20th century and was also specifically introduced to Australia in the 1960s, and it has now also invaded Italy. We used CLIMEX to model the climatic niche of T. mitsukurii to estimate its global potential distribution. We found that T. mitsukurii should be able to significantly expand its range globally, and that there is a significant degree of overlap in the projected ranges of T. mitsukurii, T. japonicus and H. halys. From a biological control perspective, this implies that the two Trissolcus species may be able to help mitigate the potential impacts of H. halys.

Exploration for olive fruit fly parasitoids across Africa reveals regional distributions and dominance of closely associated parasitoids.

The olive fruit fly, Bactrocera oleae, has been a key pest of olives in Europe and North America. We conducted the largest exploration for parasitoids associated with the fly across Sub-Saharan Africa (Kenya, Namibia, and South Africa) including some of the fly's adjoining regions (Canary Islands, Morocco, Réunion Island and Tunisia). From Sub-Saharan regions, four braconids were collected: Bracon celer, Psytallia humilis, P. lounsburyi, and Utetes africanus. Results showed that their regional dominance was related to climate niches, with P. humilis dominant in hot semi-arid areas of Namibia, P. lounsburyi dominant in more tropical areas of Kenya, and U. africanus prevalent in Mediterranean climates of South Africa. Psytallia concolor was found in the Canary Islands, Morocco and Tunisian, and the Afrotropical braconid Diachasmimorpha sp. near fullawayi on Réunion Island. Furthermore, we monitored the seasonal dynamics of the fly and parasitoids in Cape Province of South Africa. Results showed that fruit maturity, seasonal variations in climates and interspecific interactions shape the local parasitoid diversity that contribute to the low fly populations. The results are discussed with regard to ecological adaptations of closely associated parasitoids, and how their adaptations impact biocontrol.

Life History and Rearing of Anastatus orientalis (Hymenoptera: Eupelmidae), an Egg Parasitoid of the Spotted Lanternfly (Hemiptera: Fulgoridae).

To support efforts to manage and contain spotted lanternfly (SLF), Lycorma delicatula White (Hemiptera: Fulgoridae), research is being conducted to develop classical biological control methods. To date, two potential biocontrol agents from China have been identified: an egg parasitoid, Anastatus orientalis, and a nymphal parasitoid, Dryinus sinicus Olmi (Hymenoptera: Dryinidae). The research detailed here focuses on investigating the biology and rearing of A. orientalis to assess its potential efficacy in a biocontrol program and optimize its rearing. Female wasps lived significantly longer than male wasps (68 and 23 d, respectively) and females produced an average of 94 total progeny that successfully emerged as adults, with most progeny produced between weeks one and four of the females' lives. The sex ratio of the progeny, with no re-mating, was initially highly female-biased but became progressively more male-biased, likely due to sperm depletion. There was no evidence of additional mortality to SLF eggs from wasp host feeding, but the data were highly variable and the sample size was small. There was high parasitoid emergence when oviposition conditions mimicked mid-September Beijing temperature and photoperiod; however, there was little emergence under 25°C and long-day conditions because most progeny entered a diapause. Storage of parasitized eggs in 5°C chill lowered parasitoid emergence rates. Lastly, there was no evidence that storing field-collected SLF egg masses in 5°C for 10 mo prior to parasitization affected parasitism rates. These findings inform our rearing protocol for A. orientalis and facilitate our testing of this species as a potential biological control agent for SLF.

Exploratory Survey of Spotted Lanternfly (Hemiptera: Fulgoridae) and Its Natural Enemies in China.

An invasive population of spotted lanternfly (SLF), Lycorma delicatula White, was first noted in North America in Pennsylvania in 2014, and by September 2020 populations had spread to six additional states. To develop a biocontrol program to aid in the management of the pest, exploratory surveys for SLF natural enemies in its native range were carried out in 27 provinces and other administrative regions of China from 2015 to 2019. Naturally laid egg masses were collected and sentinel SLF egg masses were deployed to attract egg parasitoids, and yellow sticky traps were used to collect SLF nymphs to discover and determine the parasitism rates of nymphal parasitoids. Results show that SLF is widely distributed in China (22 provinces and regions) and that the population densities in northeast China are higher than in southern and western China. An egg parasitoid, Anastatus orientalis Yang (Hymenoptera: Eupelmidae), and a nymphal parasitoid, Dryinus sinicus Olmi (Hymenoptera: Dryinidae), were collected. Anastatus orientalis was reared from SLF eggs in seven provinces in China with parasitoid emergence rates ranging from 4.0 to 15.5% (or 17.6 to 37.3% if including only egg masses that had at least some parasitism). There were significant differences in parasitoid emergence rates between sites associated with factors including habitat and host plants. Dryinus sinicus was discovered in eight cities across six provinces. The percentage of SLF nymphs parasitized by D. sinicus were 31.1, 23.3, and 0% in Tai'an, Shandong Province, Beijing City, and Yan'an, Shaanxi Province, respectively. These two parasitoids are promising natural enemies that are being considered as potential biocontrol agents of invasive populations of SLF.

Optimizing Parasitoid and Host Densities for Efficient Rearing of Ontsira mellipes (Hymenoptera: Braconidae) on Asian Longhorned Beetle (Coleoptera: Cerambycidae).

Ontsira mellipes Ashmead is a gregarious larval ectoparasitoid of woodboring cerambycids. It is native to North America but can readily attack the exotic Asian longhorned beetle, Anoplophora glabripennis (Motschulsky). This study aimed to develop an efficient rearing system for this parasitoid, as a potential novel association biocontrol agent for the beetle, by investigating the effects of different densities of host (two, three, or four larvae) and parasitoid (one, two, three, four, five, six, seven, and eight female wasps) on Ontsira's parasitization efficiency and reproductive outcomes. Results showed that overall parasitism and total numbers of parasitized hosts or progeny produced increased with host and/or parasitoid densities, but the number of parasitized hosts or progeny produced per female parasitoid decreased with parasitoid density at each given host density. Nonlinear regression indicated a consistent pattern of mutual interference as parasitoid density increased. Additional experiments showed that superparasitism (indirect interference) did not occur probably because the parasitoid detects hosts through vibration cues from host feeding and attacked (thus paralyzed) hosts are no longer detectable. Thus, the interference probably results from direct or exploitative competition. Interestingly, female parasitoids responded to increased parasitoid density with a significant increase in clutch size. Overall, per capita parasitization efficiency or reproductive outcomes were optimized at a low parasitoid-host ratio but with large group size of hosts and parasitoids. Therefore, an optimal combination of exposing three or four parasitoids to four hosts is proposed for efficient mass-rearing of this parasitoid.

Season-Long Monitoring of the Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) Throughout the United States Using Commercially Available Traps and Lures.

Reliable monitoring of the invasive Halyomorpha halys abundance, phenology and geographic distribution is critical for its management. Halyomorpha halys adult and nymphal captures on clear sticky traps and in black pyramid traps were compared in 18 states across the Great Lakes, Mid-Atlantic, Southeast, Pacific Northwest and Western regions of the United States. Traps were baited with commercial lures containing the H. halys pheromone and synergist, and deployed at field sites bordering agricultural or urban locations with H. halys host plants. Nymphal and adult captures in pyramid traps were greater than those on sticky traps, but captures were positively correlated between the two trap types within each region and during the early-, mid- and late season across all sites. Sites were further classified as having a low, moderate or high relative H. halys density and again showed positive correlations between captures for the two trap types for nymphs and adults. Among regions, the greatest adult captures were recorded in the Southeast and Mid-Atlantic on pyramid and sticky traps, respectively, with lowest captures recorded in the West. Nymphal captures, while lower than adult captures, were greatest in the Southeast and lowest in the West. Nymphal and adult captures were, generally, greatest during July-August and September-October, respectively. Trapping data were compared with available phenological models showing comparable population peaks at most locations. Results demonstrated that sticky traps offer a simpler alternative to pyramid traps, but both can be reliable tools to monitor H. halys in different geographical locations with varying population densities throughout the season.

Host Kairomones Influence Searching Behavior of Trissolcus japonicus (Hymenoptera: Scelionidae), a Parasitoid of Halyomorpha halys (Heteroptera: Pentatomidae).

The brown marmorated stink bug, Halyomorpha halys (Stål), is a highly polyphagous species native to Asia that has become a serious invasive agricultural and nuisance pest across North America and Europe. Classical biological control host range evaluations have revealed egg parasitoid Trissolcus japonicus (Ashmead) to be the primary candidate biocontrol agent for field release against H. halys. However, these evaluations only provide us with the physiological host range of T. japonicus. Other Trissolcus species have demonstrated that contact kairomones from different host species elicit varied responses in the parasitoids' host foraging behaviors. To assess T. japonicus response to host kairomones, mated naive females were exposed to leaf surfaces contaminated with adult kairomones from its preferred host, H. halys, or from a native nontarget host, Podisus maculiventris (Say) (Heteroptera: Pentatomidae). Red maple, apple, and soybean were used as plant substrate treatments. The wasp's residence time on the leaf surface, linear walking velocity, and angular walking velocity were observed and measured using Noldus EthoVision XT tracking software. Within each leaf treatment, T. japonicus displayed stronger behavioral responses on leaves contaminated with contact kairomones from H. halys. The parasitoid resided on H. halys contaminated leaves for approximately twice as a long as it did on P. maculiventris contaminated leaves. Further, both species' kairomones elicited significant decreases in parasitoid walking velocity on all tested substrate types. Overall, our study suggests that kairomone-based behavioral studies can be used to further evaluate the host specificity of T. japonicus and can be an invaluable supplement to classical biocontrol host range testing regimes.

Footprints and Ootheca of Lycorma delicatula Influence Host-Searching and -Acceptance of the Egg-Parasitoid Anastatus orientalis.

The spotted lanternfly, Lycorma delicatula White (1845) (Hemiptera: Fulgoridae), is an invasive insect that was first reported in North America in Berks County, Pennsylvania, in 2014. It is a polyphagous phloem feeder that attacks over 70 plant species, threatening the agricultural, lumber, and ornamental industries of North America. Infestations of the pest have been reported in several U.S. counties, and a lack of endemic predators and parasitoids feeding on L. delicatula suggests a release from natural enemies in the invaded range. An egg-parasitoid Anastatus orientalis (Hymenoptera: Eupelmidae) was reported attacking L. delicatula at high rates in its native range and may play a key role in reducing its populations there. To better understand the foraging behavior of A. orientalis, a series of behavioral experiments were conducted to determine successful parasitism and behavioral responses to traces left by adult L. delicatula and to the oothecae which cover their eggs. Our results suggest that wasps detected chemical traces left by L. delicatula adults while walking on surfaces and exhibited a strong arrestment response. Moreover, wasps preferred to oviposit in egg masses with intact oothecae. The implications of these findings are herein discussed with regard to the exploitation of host kairomones by foraging wasps, as well as to its ability to overcome host structural defenses.

Counties not countries: Variation in host specificity among populations of an aphid parasitoid.

Parasitic wasps are among the most species-rich groups on Earth. A major cause of this diversity may be local adaptation to host species. However, little is known about variation in host specificity among populations within parasitoid species. Not only is such knowledge important for understanding host-driven speciation, but because parasitoids often control pest insects and narrow host ranges are critical for the safety of biological control introductions, understanding variation in specificity and how it arises are crucial applications in evolutionary biology. Here, we report experiments on variation in host specificity among 16 populations of an aphid parasitoid, Aphelinus certus. We addressed several questions about local adaptation: Do parasitoid populations differ in host ranges or in levels of parasitism of aphid species within their host range? Are differences in parasitism among parasitoid populations related to geographical distance, suggesting clinal variation in abundances of aphid species? Or do nearby parasitoid populations differ in host use, as would be expected if differences in aphid abundances, and thus selection, were mosaic? Are differences in parasitism among parasitoid populations related to genetic distances among them? To answer these questions, we measured parasitism of a taxonomically diverse group of aphid species in laboratory experiments. Host range was the same for all the parasitoid populations, but levels of parasitism varied among aphid species, suggesting adaptation to locally abundant aphids. Differences in host specificity did not correlate with geographical distances among parasitoid populations, suggesting that local adaption is mosaic rather than clinal, with a spatial scale of less than 50 kilometers. We sequenced and assembled the genome of A. certus, made reduced-representation libraries for each population, analyzed for single nucleotide polymorphisms, and used these polymorphisms to estimate genetic differentiation among populations. Differences in host specificity correlated with genetic distances among the parasitoid populations.

Nosema maddoxi sp. nov. (Microsporidia, Nosematidae), a Widespread Pathogen of the Green Stink Bug Chinavia hilaris (Say) and the Brown Marmorated Stink Bug Halyomorpha halys (Stål).

We describe a unique microsporidian species that infects the green stink bug, Chinavia hilaris; the brown marmorated stink bug, Halyomorpha halys; the brown stink bug, Euschistus servus; and the dusky stink bug, Euschistus tristigmus. All life stages are unikaryotic, but analysis of the consensus small subunit region of the ribosomal gene places this microsporidium in the genus Nosema, which historically has been characterized by diplokaryotic life stages. It is also characterized by having the reversed arrangement of the ribosomal gene (LSU -ITS- SSU) found in species within the "true Nosema" clade. This microsporidium is apparently Holarctic in distribution. It is present in H. halys both where it is native in Asia and where it is invasive in North America, as well as in samples of North American native C. hilaris collected prior to the introduction of H. halys from Asia. Prevalence in H. halys from mid-Atlantic, North America in 2015-2016 ranged from 0.0% to 28.3%, while prevalence in C. hilaris collected in Illinois in 1970-1972 ranged from 14.3% to 58.8%. Oral infectivity and pathogenicity were confirmed in H. halys and C. hilaris. Morphological, ultrastructural, and ecological features of the microsporidium, together with a molecular phylogeny, establish a new species named Nosema maddoxi sp. nov.

Phylogeography of the Wheat Stem Sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae): Implications for Pest Management.

The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), is a key pest of wheat in the northern Great Plains of North America, and damage resulting from this species has recently expanded southward. Current pest management practices are inadequate and uncertainty regarding geographic origin, as well as limited data on population structure and dynamics across North America impede progress towards more informed management. We examined the genetic divergence between samples collected in North America and northeastern Asia, the assumed native range of C. cinctus using two mitochondrial regions (COI and 16S). Subsequently, we characterized the structure of genetic diversity in the main wheat producing areas in North America using a combination of mtDNA marker and microsatellites in samples collected both in wheat fields and in grasses in wildlands. The strong genetic divergence observed between North American samples and Asian congeners, in particular the synonimized C. hyalinatus, did not support the hypothesis of a recent American colonization by C. cinctus. Furthermore, the relatively high genetic diversity both with mtDNA and microsatellite markers offered additional evidence in favor of the native American origin of this pest. The genetic diversity of North American populations is structured into three genetic clusters and these are highly correlated with geography. Regarding the recent southern outbreaks in North America, the results tend to exclude the hypothesis of recent movement of damaging wheat stem sawfly populations from the northern area. The shift in host plant use by local populations appears to be the most likely scenario. Finally, the significance of these findings is discussed in the context of pest management.