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Abstract Brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Penta-tomidae), is a highly polyphagous and invasive insect pest with more than 300 plant species as hosts, including a wide range of economic crops. To date, several egg parasitoid species are reported to attack BMSB. In this study, two species of Trissolcus (Hymenoptera: Platygastridae) and one Anastatus (Hymenoptera: Eupelmidae) were recovered from field exposed BMSB sentinel eggs in Beijing, China. The wasps’ small size of only 1.5 mm and 4 mm in length make them difficult to identify morphologically and required taxonomist for identification of specific species. In addition, these parasitoids have morphology sibling species and have been misidentified several times in China. To overcome these problems, a molecular method with species-specific primers designed for the COI gene has been developed to identify Trissolcus, Anastatus and their host samples from field collected samples. After successful morphological confirmation with experts, DNA extractions were carried out from these samples. PCR amplification using published primers for T. japonicus, A. japonicus and BMSB specimens confirmed the species. As for T. cultratus, species specific primers TCYF and TCYR were developed which produce 340-bp PCR products length while no positive amplifications found in other wasps and host. Sensitivity analysis of markers revealed that TCYF and TCYR primers could detect as low a DNA template concentration as 0.00025 ng/μL. This indicates that PCR with these primers specifically and sensitively differentiates T. cultratus specimens from other similar wasp species. All the primers tested in this study could discriminate between parasitized and non-parasitized BMSB eggs. This molecular identification method shows promise for conveniently identifying Trissolcus and Anastatus species in host-parasitoid associations and accurately evaluating parasitism rates in the field.

Simple Summary: The brown marmorated stink bug, Halyomorpha halys, is an invasive pest of agricultural crops, ornamentals, and human structures. In its native range, populations are suppressed primarily by parasitoid wasps that attack the egg stage. A promising adventive parasitoid, the samurai wasp, Trissolcus japonicus, has become established in the U.S., including Utah. According to ecological models, Utah is marginally suitable for the samurai wasp and poses unique challenges to its establishment from extreme climates and high elevation. Biological control enhancement efforts, such as deploying stink bug kairomones to attract parasitoids, may lead to the enhanced suppression of the brown marmorated stink bug. To evaluate the efficacy of this approach, experimental lures loaded with varying blends and release rates of stink bug kairomones were tested in field and mesocosm trials. This study found low parasitism in the field, while mesocosm trials demonstrated the efficacy of a single- and dual-compound blend at the 10 mg load rate for the attraction of the samurai wasp. These results support the validity of using rubber septa as a release device for kairomones of stink bugs and provide a baseline for future work on attracting samurai wasps with lures in a field environment. In its native range, Halyomorpha halys (Stål) is suppressed by parasitoids in the genus Trissolcus (Hymenoptera: Scelionidae). Trissolcus native to Utah have demonstrated low parasitism of H. halys, while adventive Trissolcus japonicus (Ashmead) have shown parasitism of up to 20%. Custom rubber septa lures containing stink bug kairomones, n-tridecane (attractant), and (E)-2-decenal (repellent), at 100%, 90%, and 80% levels of attractant (10 mg load rate), were placed adjacent to sentinel H. halys egg masses in northern Utah field trials. Egg masses were evaluated for the presence and intensity (proportion of parasitized eggs) of parasitism. Parasitism by T. japonicus and T. euschisti (Ashmead) was low; however, the 100% lure showed double the parasitism of the control and more than three times that of the 90% and 80%. Two-way choice mesocosm trials in the laboratory evaluated previous lures and a lower load rate of 5 mg—100% attractant treatment. Lures of 10 mg at 100% and 80% were more attractive to T. japonicus than the control, while 5 mg at 100% and 10 mg at 90% showed no significant attraction. Our results support a proof-of-concept of rubber septa as release devices for kairomones to attract T. japonicus and provide a baseline for future field-based studies. [ABSTRACT FROM AUTHOR]

Adventive populations of Trissolcus japonicus (Ashmead) have been detected in the eastern and western United States including the western states of Washington, Oregon, California, and Utah. These populations may provide classical biological control for the invasive brown marmorated stink bug, Halyomorpha halys (Stål), which can cause economic loss to many specialty crops in western North America. Idaho has not previously been surveyed for the exotic T. japonicus or native parasitoids of H. halys. In July 2021, T. japonicus was discovered emerging from wild H. halys egg masses in Star, Idaho (43.69788, −116.49427), and was detected on yellow sticky cards from July to September. This is the first record of T. japonicus in the state of Idaho. T. japonicus constituted only a small portion of Trissolcus species detected; other species included T. euschisti (Ashmead), T. hullensis (Harrington), and T. utahensis (Ashmead). Genetic population level analysis of T. japonicus specimens from Idaho supports the likelihood of its expansion inland from the west coast, inhabiting ecozones previously considered unsuitable due to high temperatures and low humidity. This report opens the prospect of an effective biological control agent for H. halys in Idaho and potentially other hot and dry geographic regions and expands documentation of the presence of adventive T. japonicus populations in North America. [ABSTRACT FROM AUTHOR]

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Abstract Understanding competition between scelionid parasitoids that exploit the same host may provide insight into strategies that allow coexistence on a shared resource. Competition studies typically focus on interactions between native and exotic parasitoids that do not share an evolutionary history; however, coevolved parasitoids may be more likely to demonstrate strategies to avoid or exploit a shared resource. We examined intrinsic and extrinsic competition between Asian Trissolcus japonicus (Ashmead) and T. cultratus (Mayr) (Hymenoptera: Scelionidae) associated with Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) that share an evolutionary history. Interspecific interactions were assessed by providing parasitized egg masses to each species at various intervals post‐parasitism, and measuring host acceptance, developmental suitability, and guarding behaviour. Trissolcus japonicus showed high acceptance of parasitized hosts up to 72 h following oviposition by T. cultratus, despite a very poor developmental outcome. In contrast, T. cultratus generally avoided ovipositing in H. halys eggs containing T. japonicus early‐instar larvae but did not avoid parasitizing H. halys that contained eggs and third instar larvae. The adaptive value of this behaviour was supported by developmental outcome: T. cultratus outcompeted T. japonicus eggs but not early‐instar larvae, and a trophic shift occurred wherein T. cultratus developed as a facultative hyperparasitoid on third instar T. japonicus larvae. Trissolcus japonicus guarded egg masses 8–12× longer and displayed more aggressive interactions than T. cultratus, suggesting T. japonicus is the superior extrinsic competitor. Development as a facultative hyperparasitoid provided a competitive niche for Asian T. cultratus and confirms its instrinsic competitive superiority. This also occurs in a biologically distinct European population of T. cultratus, suggesting that facultative hyperparasitism as a competitive strategy is retained in geographically separated populations that have not coevolved with H. halys or T. japonicus.

The invasive brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an agricultural and nuisance pest in Georgia and Alabama, USA. Natural enemies may provide significant suppression of the brown marmorated stink bug, and sentinel egg masses are deployed commonly on plants in the field to measure their effects. The objective of this study was to evaluate the effect of deployment duration (2–5 d) on parasitism and predation of brown marmorated stink bug sentinel egg masses in plum, peach, blueberry, tomato, sassafras, corn, and soybean in these 2 states. Retrieved egg masses were processed to quantify rates of predation and parasitism and identify parasitoid species and predation types. Across crops, predation and parasitism were higher significantly in plum at 5 d compared to 2 d deployment but was similar in soybean regardless of exposure time in 2017. Predation and parasitism were higher significantly after 5 d of exposure compared to 2 d and 3 d whereas parasitism was significantly higher at 3 d compared to 2 d exposure in 2018 to 2020. For individual crop trials, though, effects of time of exposure were tested in different yr, sampling dates, and crops with variable results. When significant differences were detected for parasitism in plum, peach, tomato, and sassafras, a 5 d deployment resulted in higher parasitism compared to 2 d. Given the variability of factors that affect parasitism and predation under field conditions, we conclude that a 5 d deployment is optimal and a 3 d exposure time is minimal for assessing predation and parasitism. An additional benefit for a 5 d exposure is that it increases the probability of detecting hyperparasitism. [ABSTRACT FROM AUTHOR]

During field surveys in Georgia, in the 2019 and 2020 growing seasons, we investigated hazelnut orchards in four regions of Georgia: Achara, Guria, Samegrelo and Kakheti for Brown Marmorated Stink Bug (BMSB) – Halyomorpha halys (Stål)(Hemiptera: Pentatomidae). Additionally, we conducted surveys in apple and peach orchards in the Kartli and Kakheti regions to find out if there was damage caused by pentatomids and search for BMSB. Fruit damage was investigated and causes of damages were classified. Monitoring of the pest was carried out by plant beating and visual observation of trees. The BMSB was found in all visited orchards in western Georgia, while it was not detected in eastern Georgian orchards. Parasitoids were collected with sweeping nets and by rearing them from field-collected egg masses. Five species of Trissolcus Ashmead (Hymenoptera: Scelionidae), which are known parasitoids of Pentatomidae, were identified. Four of these are documented for the first time from Georgia, and two are new records for the Caucasus region. [ABSTRACT FROM AUTHOR]

Understanding competition between scelionid parasitoids that exploit the same host may provide insight into strategies that allow coexistence on a shared resource. Competition studies typically focus on interactions between native and exotic parasitoids that do not share an evolutionary history; however, coevolved parasitoids may be more likely to demonstrate strategies to avoid or exploit a shared resource. We examined intrinsic and extrinsic competition between Asian Trissolcus japonicus (Ashmead) and T. cultratus (Mayr) (Hymenoptera: Scelionidae) associated with Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) that share an evolutionary history. Interspecific interactions were assessed by providing parasitized egg masses to each species at various intervals post‐parasitism, and measuring host acceptance, developmental suitability, and guarding behaviour. Trissolcus japonicus showed high acceptance of parasitized hosts up to 72 h following oviposition by T. cultratus, despite a very poor developmental outcome. In contrast, T. cultratus generally avoided ovipositing in H. halys eggs containing T. japonicus early‐instar larvae but did not avoid parasitizing H. halys that contained eggs and third instar larvae. The adaptive value of this behaviour was supported by developmental outcome: T. cultratus outcompeted T. japonicus eggs but not early‐instar larvae, and a trophic shift occurred wherein T. cultratus developed as a facultative hyperparasitoid on third instar T. japonicus larvae. Trissolcus japonicus guarded egg masses 8–12× longer and displayed more aggressive interactions than T. cultratus, suggesting T. japonicus is the superior extrinsic competitor. Development as a facultative hyperparasitoid provided a competitive niche for Asian T. cultratus and confirms its instrinsic competitive superiority. This also occurs in a biologically distinct European population of T. cultratus, suggesting that facultative hyperparasitism as a competitive strategy is retained in geographically separated populations that have not coevolved with H. halys or T. japonicus. [ABSTRACT FROM AUTHOR]

Background: Scelionid wasps are arthropod egg parasitoids, many of which are relevant to global biosecurity. However, the scelionid fauna of Germany has not received much attention from professional taxonomists. New information: Eleven species and four genera are recorded for the first time from Germany, including species of interest to agriculture and biological control. First genus records include Baryconus Förster, Macroteleia Westwood, Paratelenomus Dodd and Probaryconus Kieffer. First species records include B. europaeus (Kieffer), Idris nigroclavatus (Kieffer), Idris semiflavus (Kieffer), M. bicolora Kieffer, M. pannonica Szabo, Paratelenomus saccharalis (Dodd), Trimorus varicornis (Walker), Trissolcus basalis (Wollaston), Trissolcus belenus (Walker), Trissolcus colemani (Crawford) and Trissolcus flavipes (Thompson). COI barcodes are identified for the first time from B. europaeus and M. bicolora. Each species is illustrated and updated world distributions are provided. Implications for agriculture are discussed. [ABSTRACT FROM AUTHOR]

Classical biological control is a pest control tool involving the release of imported natural enemies. The Sterile Insect Technique (SIT) comprises releasing sexually sterile insects of a pest into the wild population for suppression or eradication. Both these approaches are environmentally friendly and their combination can result in a synergistic impact on pest populations and improve eradication. However, stringent regulation surrounding the introduction of biological control agents limits their use in eradication owing to the perceived risk of effects on non-target organisms. We investigated the irradiation biology of the egg parasitoid Trissolcus basalis to ascertain whether sterile parasitoids could mitigate the risk of potential sustained non-target impacts. Mated female T. basalis were gamma-irradiated at doses between 120 and 150 Gy and exposed to egg masses of their host Nezara viridula throughout their lifespans. This resulted in host mortality, despite a substantial reduction in developing parasitoid offspring, which followed a negative dose–response. There was no emergence of parasitoid offspring at 140 Gy and above. Irradiation did not affect oviposition behaviour but caused an increase in longevity. Consequently, sterile parasitoids could possibly alleviate concerns regarding the irreversibility of biological control release, which promotes further investigation of their potential role in eradication. [ABSTRACT FROM AUTHOR]

Background Trissolcus Ashmead (Hymenoptera: Scelionidae) is a cosmopolitan genus of egg-parasitoid wasps associated with stink bugs (Pentatomidae, Scutelleridae, Urostylididae), many of which are important insect pests. Documentation of host associations for these wasps, which we here provide via museum specimens, can support their use as biological control agents of invasive stink bugs. New information The hosts of seven Trissolcus species are reported from China: Trissolcus cultratus (Mayr) (hosts: Hippotiscus dorsalis Stål, Pentatomidae; Urochela luteovaria Distant, Urostylididae), Trissolcus elasmuchae (Watanabe) (host: Niphe elongata (Dallas), Pentatomidae), Trissolcus japonicus (Ashmead) (hosts: Erthesina fullo (Thunberg), Pentatomidae; Rhaphigaster nebulosa (Poda), Pentatomidae), Trissolcus latisulcus (Crawford) (host: Poecilocoris latus Dallas, Scutelleridae), Trissolcus mitsukurii (Ashmead) (host: Pentatomidae), Trissolcus semistriatus (Nees von Esenbeck) (host: Eurydema sp., Scutelleridae), Trissolcus yamagishii Ryu (host: Niphe elongata (Dallas), Pentatomidae). [ABSTRACT FROM AUTHOR]

Stink bugs (Hemiptera: Pentatomidae) are primary pests in most fruit, vegetable, grain, and row crops worldwide. The polyphagous habits of these pest species compels them to forage within and between closely associated non-crop and crop habitats across farmscapes in response to changing food resources. The exotic mimosa tree, Albizia julibrissin Durazz (Fabaceae), commonly grows in thickets along roadsides and in woodlands adjacent to agricultural crops across the southeastern USA. Thus, the objective of this study was to determine if mimosa was a host plant of stink bugs in southwest Georgia. Chinavia hilaris (Say) (Hemiptera: Pentatomidae) fed and developed on mimosa during early Jul through mid-Aug. Nymphs and adults of C. hilaris fed more frequently on fruit than on leaves of mimosa. Other stink bugs viz., Euschistus servus (Say), E. tristigmus (Say), E. obscurus (Palisot), Nezara viridula (L.), Thyanta custator custator (F.), and Loxa flavicollis (Drury) (all Hemiptera: Pentatomidae), also were detected on mimosa, but only as adults feeding on fruit. Trissolcus edessae Fouts (Hymenoptera: Scelionidae) was the most prevalent parasitoid of C. hilaris eggs on mimosa, but Anastatus reduvii (Howard) (Hymenoptera: Eupelmidae) also emerged from eggs of this stink bug. Overall, 46.6% of the C. hilaris eggs found on mimosa were parasitized. In conclusion, C. hilaris is the primary stink bug species developing on mimosa in southwest Georgia, serving as a potential source of this stink bug into nearby crops. [ABSTRACT FROM AUTHOR]

The brown marmorated stink bug, Halyomorpha halys, is a polyphagous pest species of worldwide economic importance. Since the mid-1990s, it has invaded and become established in various countries outside its native Asian range. In the newly invaded areas, biological control by native natural enemies has been shown to be insufficient in the long-term control of this severe pest. Adventive populations of Trissolcus japonicus, an important biological control agent of H. halys in Asia, have been reported from North America and some European countries since the mid-2010s. This egg parasitoid species seems to follow in the wake of the establishment of H. halys populations outside their native Asian range. Here, we report the first discovery of an adventive population of T. japonicus in Germany. In 2020, adult T. japonicus were recovered from parasitized H. halys egg masses (naturally laid and sentinel egg masses) and collected in ruderal areas using an insect suction sampler. The arrival of T. japonicus in Germany, unintentional through pathways yet unknown, corroborates a northbound expansion of its range within Europe. Further field surveys will show the extent of its dispersal and establishment capacities within this new distribution area.

Halyomorpha halys (Hemiptera: Pentatomidae), native to East Asia, has become a globally invasive pest, as a serious threat to agricultural production and a notorious nuisance pest in urban areas. Considerable efforts have been made so far to develop effective pest control measures to prevent crop damage. Biological control of this invasive stink bug by egg parasitoids has proven to be the most environmentally sustainable long-term solution. Knowledge of the native egg parasitoid fauna is of key importance when implementing a biological control program. Therefore, the main objective of our study was to detect egg parasitoid species associated with H. halys in the Goriška region (Western Slovenia) and to evaluate their impact on the pest population under field conditions. In the years 2019 and 2020, around 4600 H. halys eggs were collected in the wild and more than 3400 sentinel eggs were exposed to detect parasitoids in the field. Five egg-parasitoid species emerged from H. halys eggs: Anastatus bifasciatus (Hymenoptera: Eupelmidae), Telenomus sp., Trissolcus basalis, Trissolcus mitsukurii (Hymenoptera: Scelionidae) and Ooencyrtus telenomicida (Hymenoptera: Encyrtidae), all of them are new records for Slovenia. The native species, An. bifasciatus, dominated in urban and suburban areas, while non-native Tr. mitsukurii prevailed in agricultural areas. Overall parasitism rates of naturally laid eggs by the parasitoid species complex in 2019 and 2020 was 3.0 and 14.4%, respectively. Rapid recruitment of native parasitoids, early detection of an effective alien parasitoid species and increasing overall parasitism rates are very encouraging results, which need to be followed and verified in future research.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is an invasive alien species and a key agricultural pest. Its native parasitoids (Trissolcus japonicus Ashmead and Tr. mitsukurii Ashmead) have been registered in several countries where H. halys brought dramatic economic losses and where biological control is considered to be the most effective long-term solution. By searching for stink bug egg masses and exposing sentinel egg masses, we monitored the distribution of native and exotic egg parasitoids in Trentino-Alto Adige (Italy), an area where both the host and parasitoids are in expansion. We recorded ten pentatomids, seven parasitoid species, with the first report of Tr. japonicus in this area and a hyperparasitoid. In the assemblage, Anastatus bifasciatus (Geoffroy) and Tr. mitsukurii were the dominant parasitoids, with a different distribution in terms of context and host plants. Sycamore was the host plant where the highest number of naturally laid parasitized egg masses (26%) were recorded. Trissolcus mitsukurii showed the highest parasitism rate, and was often found in apple orchards. The emergence of exotic parasitoids showed a temporal delay compared to native ones. Sequence analysis of 823 bp of the CO1 mitochondrial gene revealed that the recovered Tr. japonicus and Tr. mitsukurii harbored one single haplotype each. These haplotypes were previously found in 2018 in Northern Italy. While sentinel egg masses proved to be very effective in tracking the arrival of exotic Trissolcus species, the collection of stink bug egg masses provided fundamental data on the plant host species. The results lend strong support to the adaptation of exotic Trissolcus species to the environmental conditions of the range of introduction, providing new information on plant host-associations, fundamental for the development of biological control programs.

The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive agricultural and nuisance pest that has established across much of the United States and caused significant crop losses in the Mid-Atlantic region. While it has been monitored extensively using ground-deployed pheromone traps, the vertical distribution of its life stages in the canopy of wild tree hosts has not been examined. In Virginia, small pyramid traps baited with 'low-dose' H. halys pheromone lures were deployed via a pulley system at the lower, mid-, and upper canopy of female tree of heaven (Ailanthus altissima (Mill.) Swingle) in 2016 and 2017 and male A. altissima and hackberry (Celtis occidentalis L.) in 2017. Weekly captures of adults and nymphs were recorded throughout each season. Each year, additional female A. altissima trees were felled during the two main periods of H. halys oviposition. The number and relative locations of all pentatomid egg masses found on foliage were recorded and any parasitoids that emerged from them were identified. Halyomorpha halys adults and nymphs were captured in greatest numbers in upper canopy traps and in lowest numbers in traps near the tree base. More H. halys egg masses were collected from mid-canopy than from the lower or upper canopy. The adventive egg parasitoid, Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), emerged most frequently from egg masses found at mid-canopy and was not recovered from those in the lower canopy. Results are discussed in relation to the foraging ecology of H. halys and its natural enemies, including TT. japonicus. [ABSTRACT FROM AUTHOR]

Halyomorpha halys (Stål) (Heteroptera: Pentatomidae), the brown marmorated stink bug (BMSB), is a polyphagous fruit and vegetable pest from eastern Asia and now invasive in the United States and Europe. Earlier research revealed that the main volatile from hexane egg extracts of a western North American pentatomid, Euschistus conspersus Uhler, to which two native scelionid egg parasitoids, Telenomus podisi Ashmead and Trissolcus erugatus Johnson are highly attracted, was methyl (2 E ,4 Z)-2,4-decadienoate, the major component of the conspecific male-produced aggregation pheromone. Conversely, extracts of BMSB eggs lacked the male-produced sesquiterpenoid H. halys pheromone components but contained C16,18,20 aldehydes (hexadecanal, octadecanal, and eicosanal); both egg-surface extracts of BMSB eggs and the C16,18,20 synthetic aldehyde blend repelled the female parasitoids. The goal of the present research was to manipulate egg-surface volatiles to induce the scelionid egg parasitoids to adopt BMSB eggs as a host. Here it was demonstrated that individual females of both parasitoids could be conditioned to H. halys egg-surface aldehydes in Y-tube olfactometer experiments, and this positive memory lasted 3–4 d. Furthermore, conditioned wasps successfully parasitized fresh H. halys eggs in no choice tests, and their offspring continued to successfully parasitize fresh H. halys eggs for 2–3 more generations. Eventually, both the individual and generational memories faded. Unconditioned female parasitoids were not attracted to H. halys egg extract or the synthetic blend of egg-surface aldehydes, nor did they parasitize BMSB eggs. Theoretical and practical implications of the research are discussed in the contexts of Hopkins' host selection principle, biological control, and instinct evolution. [ABSTRACT FROM AUTHOR]

Background A parasitoid wasp, Trissolcus solocis Johnson, was recorded parasitising eggs of the invasive stink bug Halyomorpha halys (Stål), in the United States. This is the first record of this species parasitising eggs of H. halys. New information First record of Trissolcus solocis parasitising Halyomorpha halys eggs in the United States and first record of T. solocis in Alabama. [ABSTRACT FROM AUTHOR]

The establishment of invasive Halyomorpha halys (Stål) outside of its native range may impact native species assemblages, including other pentatomids and their scelionid parasitoids. This has generated interest in defining species diversity and host‐parasitoid associations in this system to better understand the impact of invasive alien species on trophic interactions in invaded regions. Information on scelionid–pentatomid associations in natural habitats is lacking, and species‐level identification of these associations can be tenuous using rearing and dissection techniques. Naturally occurring pentatomid eggs were collected in areas where H. halys has established in Canada and were analysed using a modified DNA barcoding approach to define species‐level trophic interactions. Identification was possible for >90% of egg masses. Eleven pentatomid and five scelionid species were identified, and trophic links were established. Approximately 70% of egg masses were parasitized; parasitism and parasitoid species composition were described for each species. Telenomus podisi Ashmead was the dominant parasitoid and was detected in all host species. Trissolcus euschisti Ashmead was detected in several host species, but was significantly more prevalent in Chinavia hilaris (Say) and Brochymena quadripustulata (Fabricius). Trissolcus brochymenae Ashmead and Tr. thyantae Ashmead were recorded sporadically. Parasitism of H. halys was 55%, and this species was significantly less likely to be parasitized than native pentatomids. The scelionid species composition of H. halys consisted of Te. podisi, Tr. euschisti and Tr. thyantae. Although these species cannot develop in fresh H. halys eggs, we demonstrate that parasitoids attempt to exploit this host under field conditions. [ABSTRACT FROM AUTHOR]

We report the first detection of Trissolcus japonicus, an exotic Asian egg parasitoid and the primary candidate for classical biological control of the invasive brown marmorated stink bug, Halyomorpha halys, in Canada. Twenty-eight Trissolcus japonicus emerged from an H. halys egg mass from a site heavily infested by H. halys in Chilliwack, British Columbia, in 2018. This egg mass was deployed and retrieved as part of ongoing sentinel egg mass surveys for natural enemies of H. halys from 2017-2018 in coastal and interior British Columbia (total of 1,496 egg clusters at 16 sites). The identification of T. japonicus was based on biology (high levels of successful emergence from H. halys eggs), morphology, and mitochondrial DNA sequences. Trissolcus japonicus was not detected at any other survey sites in 2017-2018; however, three species of indigenous egg parasitoids were found attending or emerging from H. halys egg masses at low levels (<4%) at several sites. The origin of the detected T. japonicus, the extent of its establishment in British Columbia, and its ultimate impact on H. halys populations remain to be determined. Nonetheless, the detection of this exotic biological control agent in Canada concurrently with regulatory review of its intentional importation and release is emblematic of the current uncertainty around regulatory control on the movement of biological control agents across borders. [ABSTRACT FROM AUTHOR]

During a survey on insect egg parasitoids in Uşak province (Turkey), parasitized egg clusters of Chlorochroa juniperina (L.) (Hemiptera: Pentatomidae) were collected on Juniperus oxycedrus L. (Cupressaceae). After emergence, the egg parasitoid was identified as Trissolcus semistriatus Nees (Hymenoptera: Scelionidae). This is the first record of this parasitoid reared from the egg masses of C. juniperina. This species has not been previously reported for T. semistriatus as a host species. Mainly eggs of Eurygaster spp. and different pentatomid species were used as hosts in mass culture of the parasitoid. Eggs of this species are acceptable as an alternative host to T. semistriatus during the summer. During 2016 and 2017, 61 egg clusters were collected for the first year and 83 egg clusters were collected for the second year. They have been determined to be parasitized by 31% and 27%, respectively, over the years. Also the rate of emergence and sex ratios were calculated as 98% and 79% in the egg clusters. According to these results, T. semistriatus has an important effect on the populations of C. juniperina under natural conditions in Uşak province of Turkey. [ABSTRACT FROM AUTHOR]

The article focuses on research into invasive organisms that predate other invasive organisms. It comments on research into the samurai wasp (Trissolcus japonicus) and whether it would target native insects as well as the brown marmorated stinkbug only to discover the wasp had independently entered the U.S. through an unknown vector. It mentions other invasive biological controls including Apoanagyrus lopezi to control the cassava mealybug, and a fungus targeting the gypsy moth.

Because hosts utilized by parasitoids are vulnerable to further oviposition by conspecifics, host guarding benefits female wasps. The present study aims to test whether female adults regulate brood guarding behaviour by host discrimination in a solitary parasitoid Trissolcus semistriatus by presenting an intact or parasitized host egg mass to a female adult. Virgin females without oviposition experience have host discrimination ability, which enables them to adjust the number of eggs laid in the hosts. Mating experience increases superparasitism by female adults, whereas mated females achieve a higher discrimination ability as a result of oviposition experience and show a lower superparasitism rate. As expected, females exhibit brood guard after parasitizing an intact host egg mass, whereas those females visiting a previously parasitized host egg mass, do not. Because the survival of eggs in superparasitized hosts is relatively low, regulating brood guarding behaviour by host discrimination is adaptive for female wasps. [ABSTRACT FROM AUTHOR]

Halyomorpha halys (Stål) (Heteroptera: Pentatomidae), the brown marmorated stink bug (BMSB), is an invasive pest in the U.S., where it has been largely unaffected by natural enemies. Using rinsed and unrinsed, frozen and fresh egg masses in laboratory bioassays, we studied how surface chemicals on the eggs of H. halys might suppress parasitism by the native North American scelionid parasitoids, Telenomus podisi Ashmead and Trissolcus erugatus Johnson (Hymenoptera: Scelionidae). Parasitism of fresh-rinsed and fresh-unrinsed H. halys eggs was not observed in laboratory bioassays. However, both Te. podisi and Tr. erugatus parasitized significantly more frozen-rinsed eggs (59.6% and 71.1%, respectively) than frozen-unrinsed eggs (27.9% and 46.5% respectively). Some of these parasitoids of both species that successfully emerged from frozen-rinsed and frozen-unrinsed eggs were subsequently able to develop in fresh-unrinsed H. halys eggs for at least four generations, with parasitism starting around 30% and 40% to Te. podisi and Tr. erugatus respectively, but decreased on subsequent ones. We conclude that the success of indigenous egg parasitoids in successfully parasitizing the invasive H. halys in North America may be initially limited by compounds present on the surface of BMSB eggs, and that native parasitoids can learn to recognize the exotic BMSB eggs under specific circumstances. Knowledge of the semiochemistry of egg parasitism increases the likelihood that it may be possible to select native parasitoids for biological control of H. halys and other invasive pests. [ABSTRACT FROM AUTHOR]

When an accidentally introduced pest establishes in the invaded area, native natural enemies may adapt to the new host. A decade after the accidental introduction of the brown marmorated stink bug, Halyomorpha halys, in Europe, two generalist native egg parasitoids, the eupelmid Anastatus bifasciatus and the encyrtid Ooencyrtus telenomicida, have been recorded from this invasive agricultural pest in the field. Both species are able to complete development to the adult stage within the new host. Trissolcus basalis (Platygastridae = Scelionidae), which is not associated with H. halys in the field, was reared from freeze-killed sentinel eggs placed on soybean plants in central Italy. We tested in a Y-tube olfactometer the behavioural responses of these egg parasitoids to volatiles from H. halys adults and from Vicia faba plants attacked by H. halys. Both A. bifasciatus and O. telenomicida positively responded to adult H. halys male volatiles and to H. halys-induced plant volatiles, indicating ability to exploit cues associated with the new host for egg location, whereas T. basalis only reacted to female volatiles. A. bifasciatus and O. telenomicida are generalist egg parasitoids, showing a much wider host range when compared to T. basalis. On the other hand, platygastrid egg parasitoids from the native area of H. halys, considered for classical biological control, may be too risky due to the possibility of attacking non-target species, including predaceous stink bugs. Therefore, indigenous A. bifasciatus and O. telenomicida are presently under evaluation for augmentative biological control of H. halys in Europe. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Plants respond to insect attack by emission of volatile organic compounds, which recruit natural enemies of the attacking herbivore, constituting an indirect plant defence strategy. In this context, the egg parasitoid Trissolcus basalis is attracted by oviposition-induced plant volatiles emitted by Vicia faba plants as a consequence of feeding and oviposition by the pentatomid host Nezara viridula. However, this local tritrophic web could be affected by the recent invasion by the alien pentatomid bug Halyomorpha halys, an herbivore that shares the same environments as native pentatomid pests. Therefore, we investigated in laboratory conditions the possible impact of H. halys on the plant volatile-mediated signalling in the local tritrophic web V. faba- N. viridula- T. basalis. We found that T. basalis wasps were not attracted by volatiles induced in the plants by feeding and oviposition activities of H. halys, indicating specificity in the wasps' response. However, the parasitoid attraction towards plant volatiles emitted as a consequence of feeding and oviposition by the associated host was disrupted when host, N. viridula, and non-associated host, H. halys, were concurrently present on the same plant, indicating that invasion by the alien herbivore interferes with established semiochemical webs. These outcomes are discussed in a context of multiple herbivory by evaluating the possible influences of alien insects on local parasitoid foraging behaviour. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is native to Asia and has become a severe agricultural and nuisance pest in the U.S. Therefore, foreign exploration was conducted in Asia to identify potential classical biological control agents. Several Trissolcus spp. (Hymenoptera: Scelionidae) parasitize H. halys eggs in Asia and are being evaluated for potential release in the U.S. Since H. halys has invaded regions that experience sub-zero winter temperatures, cold tolerance is important for evaluation of Trissolcus spp. Our study compared the cold tolerance of populations of T. japonicus and T. cultratus , in order to assess relative suitability of the populations for release. We used thermocouple thermometry to determine the supercooling point and lower lethal temperature after brief exposure to cold temperature for each population. In addition, we subjected adult T. japonicus to a short photoperiod and low temperature regime, which increases cold tolerance in H. halys , to observe whether these conditions cause a change in cold tolerance in the parasitoid. We found that populations of both species froze and survived at colder temperatures than those reported for H. halys. In addition, there were no ecologically relevant differences in the temperature at which freezing or survival occurred among populations of either species, indicating that these populations are equally cold tolerant and suitable for introduction. Finally, T. japonicus does not acclimate by increasing cold tolerance in response to conditions that increase cold tolerance in H. halys, suggesting that the above-mentioned measures of cold tolerance are ecologically relevant. [ABSTRACT FROM AUTHOR]

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 FTSW, water stress was applied as mild (FTSW), moderate (FTSW) and severe (FTSW). Bioassays with plants under abiotic stress alone showed that egg parasitoids are more attracted by FTSW plants than by well-watered plants. When plants were under abiotic and biotic stress interactions, the egg parasitoids are more attracted by FTSW and FTSW 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. [ABSTRACT FROM AUTHOR]

Wolbachia is a maternally transmitted intracellular symbiont which causes reproductive distortions in the arthropods it infects. In recent years there has been an increasing interest in using Wolbachia as a potential tool for biological control by genetic manipulation of insect pests. In the present paper we report Wolbachia infection in several Trissolcus wasps (Hymenoptera: Scelionidae) which are important egg parasitoids of the sunn pest, Eurygaster integriceps Puton (Heteroptera: Scutellaridae). We used DNA sequence data for a gene encoding a surface protein of Wolbachia (wsp) not only to confirm Wolbachia infection but also to discriminate Wolbachia strains. Phylogenetic analyses indicated that Wolbachia strains in Trissolcus species were closely related to one another and belonged to supergroup B. Determination of the infection status of various populations, the possible role of Wolbachia in causing the incompatibility and knowledge of the reproductive compatibility of Trissolcus populations is important for the success of parasitoids in sunn pest management.

The objective of this work was to determine the potential of five species of Scelionidae wasps - Telenomus podisi, Trissolcus basalis, Trissolcus urichi, Trissolcus teretis and Trissolcus brochymenae - as natural enemies of the neotropical stink bug Dichelops melacanthus, and to determine if the presence of eggs of other stink bug species influences the parasitism and development of the parasitoids. Two kinds of experiments were done in laboratory: without choice of hosts (eggs of D. melacanthus) and with choice (eggs of D. melacanthus and of Euschistus heros). Biological parameters, including proportion of parasitism, immature survivorship, progeny sex ratio, immature stage development period, and host preference were recorded. All the evaluated parasitoids can parasitize and develop on D. melacanthus eggs. The first choice of eggs did not influence the proportion of D. melacanthus eggs parasitized by Tr. basalis, Tr. teretis or Tr. brochymenae. However, D. melacanthus eggs as the first choice of Te. podisi and Tr. urichi increased, respectively, 9 and 14 times the chance for parasitism on eggs of this species. Behavioral and ecological aspects of parasitoids should be considered prior to their use in biological control programs.O objetivo deste trabalho foi determinar o potencial de cinco espécies de vespas Scelionidae - Telenomus podisi, Trissolcus basalis, Trissolcus urichi, Trissolcus teretis e Trissolcus brochymenae -, como inimigos naturais do percevejo neotropical Dichelops melacanthus, e determinar se a presença de ovos de outras espécies de percevejo tem influência sobre o parasitismo e o desenvolvimento dos parasitoides. Foram realizados dois tipos de experimentos em laboratório: sem escolha de hospedeiros (ovos de D. melacanthus) e com escolha (ovos de D. melacanthus e de Euschistus heros). Foram registrados parâmetros biológicos que incluíram: proporção de parasitismo, sobrevivência de imaturos, razão sexual da progênie, tempo de desenvolvimento dos estágios imaturos e preferência de hospedeiro. Todas as espécies de parasitóides avaliadas podem parasitar e desenvolver-se em ovos de D. melacanthus. A escolha inicial de ovos não influenciou a proporção de ovos de D. melacanthus parasitados por Tr. basalis, Tr. teretis ou Tr. brochymenae. Entretanto, para Te. podisi e Tr. urichi, a escolha inicial por ovos de D. melacanthus aumentou em 9 e 14 vezes, respectivamente, a chance de parasitismo nesta espécie. Aspectos comportamentais e ecológicos dos inimigos naturais devem ser considerados antes de sua utilização em programas de controle biológico.

Euschistus servus (Say), Chinavia hilaris (Say), and Nezara viridula (L.) (Hemiptera: Pentatomidae) are economic pests of row crops. They move within and between closely associated crop and non-crop habitats throughout the growing season in response to deteriorating suitability of their current host plants. This study was conducted to investigate parasitism of naturally occurring C. hilaris and E. servus eggs in woodland habitats and crops alongside these habitats in southwest Georgia, USA. Also, parasitism of sentinel eggs of N. viridula was examined in a woodland habitat. Ten species of parasitoids, including 7 scelionids, 2 eupelmids, and 1 encyrtid, parasitized E. servus eggs. Telenomus podisi Ashmead (Hymenoptera: Scelionidae) was the most prevalent parasitoid of E. servus eggs in each of 3 habitats: woodlands, an early-season crop, and late-season crops. In woodlands, 27.9% of E. servus eggs were parasitized by Anastatus reduvii (Howard) and A. mirabilis (Walsh & Riley) (Hymenoptera: Eupelmidae). Four species of parasitoids, including 1 scelionid, 2 eupelmids, and 1 encyrtid, parasitized C. hilaris eggs. Trissolcus edessae Fouts (Hymenoptera: Scelionidae) was the most prevalent parasitoid of C. hilaris eggs in woodlands and the only parasitoid of C. hilaris eggs in late-season crops. In woodlands, 40.7% of C. hilaris eggs were parasitized by A. reduvii and A. mirabilis. In a woodland habitat, 6.6% of N. viridula sentinel eggs were parasitized by A. reduvii females, Anastatus males, and 1 encyrtid. Anastatus species were the only parasitoids that existed primarily in woodland habitats. In conclusion, a diversity of parasitoid species parasitizes native stink bug eggs in southwest Georgia, and species of parasitoids emerging from stink bug eggs can vary by habitat. [ABSTRACT FROM AUTHOR]

Parasitoids are important natural enemies that are used in the biological control of insect herbivore pests. The egg parasitoid Trissolcus grandis Thompson (Hym. Scelionidae) is a major enemy of the Sunn pest, Eurygaster integriceps Puton (Hem. Scutelleridae), which in turn is one of the most destructive pests of wheat in the Middle East. Our objective was to develop an artificial diet to enhance the performance of T. grandis adults in biological control of the Sunn pest on wheat. We studied the combined effects of concentrations and the composition of sugars and proline on several life-history related parameters in T. grandis , including adult longevity, fecundity, fertility, sex ratio, oviposition period, the fecundity to oviposition period ratio , and reproductive index (e.g. intrinsic rate of increase) of T. grandis . Positive effects of sugar compounds and proline were observed on mean longevity in female and male wasps, as well as on offspring sex ratio (more females produced), oviposition period, fecundity, fertility and reproductive index. Our results thus reveal that the type of diet provided to T. grandis adults benefit the mass rearing efficiency of this important biological control agent. [ABSTRACT FROM AUTHOR]

Trissolcus japonicus (Hymenoptera: Scelionidae) and Trissolcus plautiae are solitary endoparasitoids in eggs of stink bugs (Hemiptera: Pentatomidae). These two closely related parasitoids differ in their degree of host specificity. With the aid of scanning electron microscopy, we examined the external morphology, distribution, and abundance of the antennal sensilla of sexes of both species to gain insights into the olfactory mechanism in relation to host selection behavior. Seven types of sensilla were recorded in both species: basiconica, trichodea, groovedpeg, sickle-shaped, chaetica, papillary, and campaniformium sensilla. Sexual dimorphism of antennal structures occurred in both species. Male antennae possessed one more flagellomere and a larger number of olfactory sickle-shaped sensilla than female antennae, indicating that sensilla may be involved in mate or host location. There was a peg gland on the fifth antennomere of male antennae. Compared with males, females had a higher number of trichodea sensilla as well as papillary sensilla, which were not found in males. These sensilla might be involved in host recognition and acceptance during the drumming behavior of both species. No qualitative differences were recorded between the species in antennal structure, or sensilla types or topographical arrangement. However, the abundance of key sensilla was significantly different between species. T. plautiae females and males had larger numbers of trichodea sensilla than those of T. japonicus. T. japonicus females possessed fewer and larger sickle-shaped sensilla compared with T. plautiae females. These differences may provide a morphological basis for understanding the process of host habitat location and recognition in these parasitoids. [ABSTRACT FROM AUTHOR]

Chinavia hilaris (Say), Euschistus servus (Say), Euschistus tristigmus (Say), and Thyanta custator custator (F.) (Hemiptera: Pentatomidae) are serious pests of crops in the southeastern United States but little is known concerning their dispersal from noncrop hosts in woodlands into crops. This 2-yr study was conducted to investigate whether elderberry [Sambucus nigra subsp. canadensis (L.) R. Bolli] in woodlands serves as a source of stink bugs dispersing into adjacent crops and to examine parasitism of C. hilaris and E. servus eggs on this plant. Elderberry was a reproductive host for each of the four stink bug species; females oviposited on plants with subsequent nymphs feeding on elderberry and developing into adults. Anastatus mirabilis (Walsh & Riley) (Hymenoptera: Eupelmidae), Anastatus reduvii (Howard), and Trissolcus edessae Fouts (Hymenoptera: Scelionidae) were prevalent egg parasitoids of C. hilaris but A. reduvii was the prevalent parasitoid of E. servus. Newly developed stink bug adults were first detected on elderberry around mid-July. Then in late July and early August, as elderberry fruit senesced and cotton bolls became available, stink bugs began dispersing from elderberry into cotton based on recapture of stink bugs on cotton that had previously been marked on elderberry. In addition, in 2015, density of C. hilaris, E. servus, and E. tristigmus was higher in cotton with elderberry than in cotton without it. Over the study, economic threshold was reached for four of seven cotton fields. Elimination of elderberry in woodlands adjacent to cotton may be a viable management tactic for control of stink bugs in cotton. [ABSTRACT FROM AUTHOR]