Behavioral responses of the egg parasitoid <Emphasis Type="Italic">Trissolcus japonicus</Emphasis> to volatiles from adults of its stink bug host, <Emphasis Type="Italic">Halyomorpha halys</Emphasis>

Halyomorpha halys, originating from East Asia, has become an important agricultural pest in northern temperate regions since its accidental introduction into North America in the mid-1990s and Europe in 2007. Trissolcus japonicus is the predominant egg parasitoid of this pest in its native range. Here, we tested the hypothesis that T. japonicus uses volatiles associated with H. halys adults during host location. The effects of these volatile compounds on H. halys adults were also assessed. Chemical analysis with GC-MS and electrophysiological analysis with GC-EAD revealed the presence of two bioactive volatile compounds from H. halys adults, n-tridecane and (E)-2-decenal. In the Y-tube assays, female T. japonicus were attracted by n-tridecane but strongly repelled by (E)-2-decenal. Furthermore, host searching time of female T. japonicus was significantly reduced when an H. halys egg mass was treated with n-tridecane and prolonged when treated with (E)-2-decenal or a mixture of (E)-2-decenal and n-tridecane. Male H. halys were significantly attracted by n-tridecane, whereas females had no response to this compound in the Y-tube assays. (E)-2-Decenal strongly repelled male and female H. halys in the Y-tube assays. We discuss the multifunctional kairomonal and other possible roles of these semiochemicals at different trophic levels in the context of intra- and inter-specific chemical communication, in the H. halys–T. japonicus system.     

Predatory ability of the ant <Emphasis Type="Italic">Crematogaster scutellaris</Emphasis> on the brown marmorated stink bug <Emphasis Type="Italic">Halyomorpha halys</Emphasis>

The pest Halyomorpha halys is a recent example of severe worldwide biological invasion. In Italy, after the first detection in 2012, it has rapidly spread and economic damage has already been reported in commercial fruit orchards, eliciting enormous concern for Italian agricultural production. As a long-term solution, biological control investigations are focusing on the potential of natural antagonists, such as generalist predators, in the invaded areas. Due to their biology, ecology and behavior, ants represent one such generalist predator potentially suitable for inflicting mortality on H. halys. In this research, Crematogaster scutellaris was used as a study model. Specifically, the effect of ant predatory behavior on the survival of all H. halys pre-imaginal stages was tested in the laboratory environment. The results suggest that C. scutellaris has a significant predatory impact on all H. halys pre-imaginal stages except for eggs. The reduction of survivorship is between 95 and 85% for instars 1 and 2 and between 38 and 52% for instars 3, 4 and 5. The different levels of predation success suggest that these ants could act as useful generalist predators when associated with other antagonists and/or other control strategies. Although further field investigations are needed, the potential of ants as biocontrol agents of invasive species in agroecosystems deserves consideration in integrated pest management programs.     

Development and fecundity of <Emphasis Type="Italic">Trissolcus japonicus</Emphasis> on fertilized and unfertilized eggs of the brown marmorated stink bug, <Emphasis Type="Italic">Halyomorpha halys</Emphasis>

Halyomorpha halys, the brown marmorated stink bug, is a serious agricultural and horticultural pest native to East Asia, which became an invasive pest in northern temperate parts of other regions in the mid-1990s. Trissolcus japonicus is a dominant egg parasitoid of H. halys in its native range. In this paper, we investigated mating, oviposition and fecundity of both virgin and mated females of H. halys. Virgin H. halys females produced unfertilized eggs, while mated females produced fertilized eggs, but mating states of adult females did not affect the number of eggs produced. We further compared the development and fecundity of T. japonicus on fertilized or unfertilized eggs of various ages. Fertilized eggs were tested continuously for up to 5 days (time to hatch), while unfertilized eggs were tested for up to 11 days (time to egg collapse). The fertilization status of the host egg had a significant effect on the development, emergence success, and sex ratio of T. japonicus progeny. A small increase in development time was observed for T. japonicus in fertilized eggs, fewer T. japonicus emerged from fertilized eggs than unfertilized eggs, and the proportion of female progeny was lower on fertilized eggs. The age of host eggs also significantly affected the development rate and fecundity of T. japonicus, with unfertilized eggs becoming more favorable than fertilized eggs as egg age increased. In summary, unfertilized H. halys eggs were better suited for T. japonicus development and fecundity, indicating their potential use in T. japonicus mass rearing.     

Pentatomid host suitability and the discovery of introduced populations of <Emphasis Type="Italic">Trissolcus japonicus</Emphasis> in Oregon

Trissolcus japonicus is an egg parasitoid of Halyomorpha halys, brown marmorated stink bug, a severe agricultural pest in the USA. T. japonicus is being evaluated in quarantine as a classical biological control agent to manage H. halys populations in the USA. To determine T. japonicus’ potential for successful management of the pest, we performed a series of no-choice and paired-host-range tests, evaluating parasitism and host recognition in ten nontarget insects. In laboratory no-choice tests, T. japonicus successfully parasitized egg masses of seven Pentatomidae native to Oregon in addition to H. halys. Mean parasitism proportions of egg masses were greater than 40% in two species, B. dimidiata and H. abbreviatus, and were statistically similar to parasitism of H. halys. However, paired-host tests identified higher proportions of parasitized H. halys egg masses compared to four other pentatomids. T. japonicus was equally attracted to volatiles produced by H. halys and other pentatomids but demonstrated significantly longer arrestment response time on surfaces with H. halys contact kairomones. Although host acceptance patterns were similar between stink bug species, our results suggest a greater potential for parasitoid development in H. halys eggs compared to the native pentatomids. During host-range testing, we detected field populations of T. japonicus at 11 sites in Portland, OR, indicating an unintentional introduction and establishment. Further work is needed to characterize its nontarget activity and dispersal patterns in areas where H. halys causes economic damage in Oregon.     

Natural biological control of <Emphasis Type="Italic">Halyomorpha halys</Emphasis> by native egg parasitoids: a multi-year survey in northern Delaware

Halyomorpha halys (Stål) is a highly polyphagous plant pest native to eastern Asia. Since its accidental introduction to the USA in the mid-1990s, it has spread across North America and caused serious economic damages. Chemical control has been a widely applied management strategy which is not sustainable on a long-term basis. A nine-year survey using sentinel and naturally laid H. halys was conducted to investigate the extent of natural biological control by parasitoids in managed and non-managed landscapes in northern Delaware, USA. Naturally laid egg masses of native pentatomids were collected to compare the resident parasitoid complex to the one attacking H. halys eggs. Mean parasitism rates of sentinel eggs were below 6% in any given year of the survey with a grand mean of 1.79%. Parasitism of naturally laid H. halys eggs was higher than that of sentinel eggs, but there was no significant difference in parasitism between years and the grand mean was 4.31%. Parasitoid species richness on sentinel and naturally laid H. halys eggs was similar but both were lower than the richness on native pentatomid eggs. H. halys eggs were parasitized by eight species in the genera Anastatus, Trissolcus, Telenomus, and Ooencyrtus. The level of parasitism by native egg parasitoids is insufficient to provide long-term control of H. halys. Trissolcus japonicus (Ashmead), an Asian egg parasitoid that has been recovered in the USA in several locations since 2014, may be the most promising candidate for long-term biological control of H. halys.     

Chemical ecology of <Emphasis Type="Italic">Halyomorpha halys</Emphasis>: discoveries and applications

There have been notable and significant advances in elucidating the chemical ecology of the invasive Halyomorpha halys (Hemiptera: Pentatomidae), brown marmorated stink bug. This highly destructive and polyphagous pest is originally from Korea, China, and Japan, but was accidentally introduced into North America and Europe. Prior to its invasion into these regions, little was known about its chemical ecology. However, since then, researchers have identified and synthesized its aggregation pheromone, documented its synergism with the pheromone of another Asian stink bug, Plautia stali, developed monitoring traps of various designs, and lures with reliable attractants have become commercially available. Furthermore, plant volatiles have been shown to have attractive, neutral, and repellent effects on attraction and retention of H. halys, and H. halys-derived volatiles have been shown to play a role in recruiting natural enemies. Finally, management strategies based on pheromone-based technology have been evaluated, including insecticide applications based on a cumulative threshold of adult captures in pheromone-baited traps, and the use of intensively baited trees in an attract-and-kill strategy to manage this pest. This review summarizes the available literature on the chemical ecology of H. halys and concludes with several research areas that should be explored in future research.     

Seasonal parasitism and host specificity of <Emphasis Type="Italic">Trissolcus japonicus</Emphasis> in northern China

The brown marmorated stink bug, Halyomorpha halys (Stål), native to China, Japan, and Korea, has emerged as a harmful invasive pest of a variety of crops in North America and Europe. The Asian egg parasitoid Trissolcus japonicus has been identified as the most promising agent for classical biological control of invasive H. halys populations. A 4-year study evaluated the fundamental and ecological host ranges of T. japonicus as well as its phenology and impact on H. halys populations in fruit orchards in its native range in northern China. In laboratory no-choice tests, developmental suitability of eight non-target host species for T. japonicus was demonstrated by the successful production of progeny on the majority (>85%) of non-target host species tested. In field-collected, naturally laid egg masses, T. japonicus was the most abundant parasitoid associated with H. halys and Dolycoris baccarum, but was also sporadically found in Plautia crossota. Furthermore, it was regularly reared from sentinel egg masses of Menida violacea, Arma chinensis, and Carbula eoa. The only species that did not support development in the laboratory and field was Cappaea tibialis. Besides the benefit of having a high impact on H. halys populations in Northern China, the risk assessment conducted in the area of origin indicates that native Pentatomidae in North America and Europe could be negatively impacted by T. japonicus. Whether the benefits of T. japonicus outweigh the possible risks will have to be evaluated based on the outcome of additional host range studies in the two invaded regions.     

Review of the chemical control research on <Emphasis Type="Italic">Halyomorpha halys</Emphasis> in the USA

The invasive brown marmorated stink bug Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) has become a serious economic pest in parts of the USA, and control tactics are often needed in order to avoid crop losses in tree fruit and other crops. Chemical control is usually the most effective and efficient tactic for preventing damage in crops. Researchers have tested a wide range of insecticides using laboratory and field experiments to determine the best options for H. halys control in the USA. This review summarizes that work and describes current practices with regard to insecticide options for H. halys.     

<Emphasis Type="Italic">Halyomorpha halys</Emphasis>, a serious threat for hazelnut in newly invaded areas

Following its first detection, Halyomorpha halys has become a key pest in many crops in NW Italy. In this area, one of the most important crops is hazelnut, in which the species can cause severe damage through feeding on nuts. Therefore, semi-field trials were carried out in NW Italy to compare the harmfulness of H. halys with that of the local hazelnut bug species, such as Gonocerus acuteangulatus, Nezara viridula, and Palomena prasina. Additionally, a 2-year field survey was conducted in hazel groves in NW Italy and W Georgia, another important hazelnut cropping area, to assess the presence and abundance of the new invasive species and to evaluate the damage at harvest. Monitoring was carried out by plant beating and by commercial traps throughout the growing season. In semi-field trials, H. halys was the most harmful species, causing the highest damage in kernels, and was able to survive and reproduce at higher rates. During field surveys in NW Italy, H. halys was sampled in groves late in the season in 2015 and, with higher populations, throughout the season in 2016. In W Georgia, bug population levels consistently increased in the 2-year period, resulting in a significant increase in damage at harvest in 2016. A similar trend is hence expected also in NW Italy in the following years. Moreover, data on individuals collected in different points of the hazelnut groves confirmed the border-driven behavior of this pest, leading to consideration of potential integrated pest management solutions.     

Possible coexistence of native and exotic parasitoids and their impact on control of <Emphasis Type="Italic">Halyomorpha halys</Emphasis>

Introduction of exotic natural enemies for biological control of invasive pests may disrupt existing ecological interactions, which may influence the outcome of biological control introductions. The interactions between Asian egg parasitoids, proposed as classical biological control agents of the highly polyphagous invasive pest Halyomorpha halys (Stål), and parasitoids native to the introduced area are largely unknown. Therefore, adult and larval interspecific competition between the exotic Trissolcus japonicus (Ashmead) and the European Anastatus bifasciatus (Geoffroy) was assessed (1) by observing aggressive interactions between adults of the two species following parasitization and (2) by providing each parasitoid species with previously parasitized H. halys egg masses at various time intervals. The results suggest that T. japonicus and A. bifasciatus engage in counterbalance competition, with the former being a superior extrinsic competitor (egg guarding and aggressiveness) and the latter being a superior intrinsic competitor (successful development from multiparasitized eggs of all ages). We suggest that the presence of T. japonicus is unlikely to have a negative impact on A. bifasciatus, and that those two species can coexist and potentially act synergistically in the biological control of H. halys.     

Pheromone-based decision support tools for management of <Emphasis Type="Italic">Halyomorpha halys</Emphasis> in apple orchards: development of a trap-based treatment threshold

The invasive brown marmorated stink bug, Halyomorpha halys (Stål), has become a serious pest in mid-Atlantic apple orchards. Because no decision support tools exist for H. halys management, calendar-based insecticide applications have been the only successful technique for mitigating H. halys injury in orchards. Following the identification of the two-component aggregation pheromone of H. halys, we conducted a study to determine whether biological information generated by traps baited with this pheromone and pheromone synergist could be used to make management decisions. In this study, experimental apple orchards were treated with a H. halys-targeted insecticide only when a predetermined cumulative threshold of either 1, 10, or 20 adults per trap was reached. Once threshold was reached, two alternate row middle sprays 1 week apart were triggered and the threshold was reset. For comparison, some orchards were also subjected to a weekly alternate row middle spray or left untreated as controls. At harvest, significantly less fruit injury was observed when treated weekly or using a threshold of 1 or 10 H. halys adults per trap to trigger insecticide applications. Orchards treated using a cumulative threshold of 20 adults per trap or when left unsprayed had significantly higher fruit injury. In addition, insecticide applications were reduced by 40% using a threshold of 10 adults per trap. Our results suggest that baited pheromone traps can be used as decision support tools to trigger insecticide applications when needed to mitigate risk and effectively manage H. halys in apple orchards.     

Field surveys of egg mortality and indigenous egg parasitoids of the brown marmorated stink bug, <Emphasis Type="Italic">Halyomorpha halys</Emphasis>, in ornamental nurseries in the mid-Atlantic region of the USA

The brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive species native to regions of China, Japan, Korea, and Taiwan. In its native and introduced range, H. halys is considered a pest of tree fruits, vegetables, legumes, and ornamental trees. The highly polyphagous nature of this insect as well as its vast dispersal capabilities, require an integrated approach to management. Here we focus on the potential impact of indigenous natural enemies on H. halys in woody ornamental nurseries in Maryland, USA. We sampled naturally field laid H. halys egg masses for mortality and parasitism rates in 2012 and 2013. Overall, egg mortality averaged 54% for both years, and increased within season and between years. The largest source of mortality was from egg parasitoids with mean parasitism rates of 30.73 and 39.63% in 2012 and 2013, respectively. Mortality from predation was much lower and averaged 4.61% by chewing and 2.53% by sucking predators. We found seven species of Hymenopteran egg parasitoids attacking H. halys eggs, with Anastatus reduvii being the dominant species comprising 61.17 and 79.12% of all parasitoids in 2012 and 2013, respectively. The observed increase in parasitism over time and female biased sex ratio of parasitoids suggests that native parasitoids may be responding to the novel host, H. halys. Consequently, the use of these native eupelmid egg parasitoids in augmentative or conservation biological control may be a viable H. halys management strategy in ornamental nurseries.     

Patterns of niche filling and expansion across the invaded ranges of <Emphasis Type="Italic">Halyomorpha halys</Emphasis> in North America and Europe

Studies of realized niche shift and model transferability in alien species usually ignore the potential effects of source populations and different invaded-range environments on niche lability. We incorporate our detailed knowledge of the native-range source populations and global introduction history of brown marmorated stink bug (Halyomorpha halys) to examine intraspecific variation in realized niche expansion and unfilling, and to investigate how niche modelling approaches are affected by that variation. Realized niche dynamics of H. halys were analyzed using an ordination method, ecological niche models (ENMs), and occurrence records from (1) East Asia, (2) North America, (3) Europe, (4) native-range source populations for North America and Europe introductions, and (5) global range. Patterns of niche filling and expansion were observed across the invaded ranges of H. halys in North America and Europe: niche unfilling (42.7 %) and expansion (0.0 %) in North America, and unfilling (80.5 %) and expansion (28.0 %) in Europe. Some invasive populations have expanded into climatically novel areas in central Europe. Results presented here provide evidence that H. halys has not yet occupied all suitable climatic habitats in North America and Europe that resemble its native range, and the central USA and most parts of Europe appear to be most at risk of H. halys spread in near future. When realized niche shifts dominated by niche unfilling, fully capturing species’ requirement by basing ENMs on native range may be more important for accurate invasion forecasts than non-native models. Caution is warranted when using the source population to estimate invasion potential.     

Effects of water stress on emission of volatile organic compounds by <Emphasis Type="Italic">Vicia faba</Emphasis>, and consequences for attraction of the egg parasitoid <Emphasis Type="Italic">Trissolcus basalis</Emphasis>

When plants are damaged by herbivorous insects, blends of volatile organic compounds (VOCs) are induced and released and can also be used by parasitoids to locate hosts. The aim was to determine whether VOCs induced by water stress affect the plant–herbivore–parasitoid system represented by broad bean (Vicia faba; Fabales: Fabaceae) stink bug (Nezara viridula; Heteroptera: Pentatomidae) egg parasitoid (Trissolcus basalis; Hymenoptera: Platygastridae). The effects of water stress (expressed as the percentage fraction of transpirable soil water [FTSW] supplied) alone and in combination with N. viridula damage (feeding plus oviposition) were determined according to: (1) the behavioural response of the egg parasitoid in a Y-tube olfactometer and (2) the plant VOCs collected and analysed by thermal desorption–gas chromatography–mass spectrometry. With pot water capacity as FTSW₁₀₀, water stress was applied as mild (FTSW₈₀), moderate (FTSW₅₀) and severe (FTSW₁₀). Bioassays with plants under abiotic stress alone showed that egg parasitoids are more attracted by FTSW₁₀ plants than by well-watered plants. When plants were under abiotic and biotic stress interactions, the egg parasitoids are more attracted by FTSW₁₀ and FTSW₅₀ plants than by well-watered plants infested with N. viridula. Considering VOCs emissions, projection to latent structures discriminant analysis (PLS-DA) separated treatments according to egg parasitoid responses. Water stress alone and in combination with biotic stress induced changes in VOC emissions of V. faba plants that attract egg parasitoids. These findings contribute to our understanding of how water stress affects the interactions between plants, insect pests and egg parasitoids.     

Osmoregulators in <Emphasis Type="Italic">Hymenaea courbaril</Emphasis> and <Emphasis Type="Italic">Hymenaea stigonocarpa</Emphasis> under water stress and rehydration

The objective of this work was to evaluate the effect of different water deficiency and rehydration levels on the concentrations of osmoregulators in two plant species (Hymenaea courbaril and H. Stigonocarpa) in the Amazon. We adopted a 2 × 5 × 5 factorial system, referring to 2 species (H. courbaril and H. stigonocarpa) and 5 stages of hydration and rehydration. The five hydration and rehydration stages were established in: (1) Control treatment E0; (2) Plants with 13 days of stress after incubation—E13; (3) Plants with 26 days of stress E26; (4) The plants that were established after 26 days after incubation and rehydrated for two days (RD2); (5) rehydrated for two days (RD4). The plants that were established after 26 days after incubation and rehydrated for four days. The experiment totaled fifty young plants with five replicates. Biochemical measurements were performed at the beginning of the experiment (E0) at 13 (E13) and 26 (E26) days after the water stress, in which the plants were rehydrated, repeating the analyses after two (RD2) and four (RD4) days. Both species increased the sucrose concentration by 18%, with a decrease of 52% in starch content. The RD4 time presented the highest mean starch concentration (0.19 mmol g^?1 of the residue for H. courbaril and 0.27 mmol g^?1 of residue for H. stigonocarpa). Increased proline concentrations were recorded for controls until RD2 for both species. For glycine betaine, the highest increases in treatments E26 and RD2 were observed for the H. courbaril species. Our rehydration period was not sufficient for total recovery of pre-stress concentrations of all studied solutes.     

A novel cold-inducible promoter,P<Emphasis Type="Italic">ThCAP</Emphasis> from <Emphasis Type="Italic">Tamarix hispida</Emphasis>, confers cold tolerance in transgenic <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Our previous studies have revealed that the ThCAP gene plays a vital role in transgenic Populus (P. davidiana × P. bolleana) in response to cold stress. However, the regulatory mechanism of ThCAP gene expression has been unclear. In this study, the 5′ flanking region of the ThCAP promoter (PThCAP) was cloned using a genome-walking method. By analyzing cis-acting regulatory elements of PThCAP, a DRE motif and MYC and MYB elements were found to be located in the promoter. To identify the regulatory elements that control the expression of the ThCAP gene promoter, a series of deletion derivatives of PThCAP, P1–P5, from the translation start code (?1538, ?1190, ?900, ?718 and ?375 bp), were fused to the GUS reporter gene, and then each deletion was stably introduced into Arabidopsis thaliana plants. Deletion analysis of the promoter suggested that only the P2 fragment had strong GUS expression in leaves and roots of A. thaliana exposed to low temperature stress. These results suggest that this 290-bp region (?1190 to ?900 bp), as an important part in PThCAP, was associated with cold tolerance of A. thaliana. Our results provide evidence for the regulatory mechanism of ThCAP gene involved in the response to cold stress, and that the gene is promising candidate gene for genetic improvement of crops.     

Cross-crop effects on larval growth,survivorship and fecundity of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis>

The cotton bollworm Helicoverpa armigera is a destructive pest that affects a variety of crop plants. Because of its polyphagous feeding habit, mobility as adults, and high fecundity, the expanding infestations of H. armigera in different crops have caused economic losses and difficulties for pest population management. In Brazil, a sequence of different crop systems in the same area and crop rotation during the year can create a spatio-temporal mosaic of crops where H. armigera can persist. However, the consequences of the simultaneous and/or alternating presence of host plants for H. armigera populations through generations are unknown. In this study, we simulated, in the laboratory, hypothetical situations for the availability of soybean and cotton crops in the landscape. We evaluated the effects of: (1) the number of generations during which a population feeds on a host-plant species; (2) the succession of host-plant species on which populations have fed for two generations; and (3) the parental host plant on the fitness of H. armigera populations. Only the current host plant on which larvae fed affected the performance of the H. armigera populations. Decrease of mortality rates during the immature period was slowed when the larvae fed on soybean. The lowest value of reproductive potential (R ₀) was found for individuals originating from mating between females and males reared in cotton. Our results indicated that pest-management and biological-control plans for H. armigera should be developed on a regional scale rather than for just a specific crop area.     

Potential of Ethiopian mustard, <Emphasis Type="Italic">Brassica carinata</Emphasis> as a trap crop for large white butterfly, <Emphasis Type="Italic">Pieris brassicae</Emphasis> infesting Indian mustard, <Emphasis Type="Italic">Brassica juncea</Emphasis>

The large white butterfly, Pieris brassicae (L.), is an important pest of Indian mustard, Brassica juncea (L.) Czern., and inflicts heavy damage to all the above ground plant parts with strong yield reducing impacts. Farmers have few practical options other than to spray insecticides to protect their crop. In this study, an attempt was made during 2012–2013 and 2013–2014 crop seasons at Ludhiana, India, to evaluate Ethiopian mustard, Brassica carinata A. Braun as a trap crop to manage this pest as an alternate pest management strategy. B. carinata borders surrounding B. juncea were compared to chemically protected B. juncea and control (without B. carinata borders) plots for their effects on P. brassicae infestation and grain yield. Oviposition preference of adult butterflies was studied in a two-choice test in field cages, while the effect of two host plants on larval performance was studied under laboratory conditions under no choice conditions. B. juncea plots bordered with B. carinata harbored significantly lower larval population compared to control B. juncea plots during both the seasons. The grain yield in the bordered plots was also significantly higher than that from control plots and was statistically non-significant from that obtained in chemically protected plots. Female butterflies showed distinct oviposition preference for B. carinata over B. juncea and the larvae reared on B. carinata completed development in shorter period and grew bigger and heavier than those reared on B. juncea. Results indicated that B. carinata has potential to be used as trap crop to manage P. brassicae.     

The potential global distribution of the brown marmorated stink bug, <Emphasis Type="Italic">Halyomorpha halys</Emphasis>, a critical threat to plant biosecurity

The brown marmorated stinkbug, Halyomorpha halys is a highly polyphagous invasive insect, which has more than 300 reported hosts, including important horticultural crops. It has spread to every Northern Hemisphere continent, most recently to Europe. Whilst there have been no reports of incursions into Southern Hemisphere countries, there have been many interceptions associated with trade and postal goods. We modelled the potential distribution of H. halys using CLIMEX, a process-oriented bioclimatic niche model. The model was validated with independent widespread distribution data in the USA, and more limited data from Europe. The model agreed with all credible distribution data. The few exceptions in the distribution dataset appeared to be transient observations of hitchhikers, or were found at the edge of the range, in regions with topographic relief that was not captured in the climatic datasets used to fit and project the model. There appears to be potential for further spread in North America, particularly in central and southern states of the USA. In Europe, there is substantial potential for further spread, though under historical climate the UK, Ireland, Scandinavia and the Baltic states of Estonia, Lithuania and Latvia appear not to be at risk of establishment of H. halys. In the Southern Hemisphere, regions with moist tropical, sub-tropical, Mediterranean and warm-temperate climates appear to be at substantial risk on each continent. The threats are greatest in prime horticultural production areas.