Effectiveness of field-exposed attract-and-kill devices against the adults of Popillia japonica (Coleoptera: Scarabaeidae): a study on duration, form and storage.

BACKGROUND: The Japanese beetle Popillia japonica Newman is an insect pest native to Japan that has spread into North America, the Azores and, recently, into continental Europe. Here, we present a study assessing the effectiveness of a long-lasting insecticide-treated net (LLIN), assembled in semiochemical-baited attract-and-kill devices (A&Ks) as a low environmental impact means to control P. japonica in the field. We compared the attractiveness of three different forms of A&Ks that were left outdoors throughout the summer, and the residence time of P. japonica landing on them. Moreover, we performed a preliminary study testing the effectiveness of new LLINs after storage. Collected data also allowed us to investigate the beetles' diel flight patterns in relation to meteorological conditions. RESULTS: Killing effectiveness of the field-exposed A&Ks declined steadily over the flight season (from 100% to 37.5%) associated with a decrease in residues of α-cypermethrin, the active ingredient in the LLINs. The different A&K forms (pyramidal, octahedral and ellipsoidal) attracted similar numbers of beetles. Individual beetles' residence time ranged from 75 to 95 s and differed slightly between A&K forms. Effectiveness of LLINs decreased by ≈30% after 1 year storage. Based on numbers landing on A&Ks, the beetles' flight activity peaked about 14:30 h and was inversely correlated with relative humidity. CONCLUSION: This study indicates that semiochemical-baited A&Ks are effective for controlling P. japonica in the field. Because of active ingredient decay, the LLINs should be replaced after 30-40 days of field exposure to ensure that the A&Ks remain fully functional. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

New insights from the virome of Halyomorpha halys (Stål, 1855).

Halyomorpha halys (Stål, 1855) (Hemiptera: Pentatomidae), the brown marmorated stink bug, is an invasive pentatomid native to East-Asia, and introduced worldwide in recent times. It is a polyphagous pest with approximately 300 host plants, which, due to its plasticity, reproductive and feeding behavior, long-distance flight, and walking as well as human-mediated dispersal ability, is able to cause significant economic and ecological damage. In several cases pest control mediated by insecticide treatments leads to unsatisfactory efficacy, mostly due to insect recovery ability. Thus, the most promising method for the long-term management of this pest has been focused with growing emphasis on classical biological control strategies. In this framework, viruses have untill now been poorly investigated in H. halys with only a single virus described from the US territory. For this reason we investigated the virome associated with a small and well described population of H. halys from Piedmont (Italy) describing for the first time 7 new viral sequences belonging to different taxonomical groups. Further studies will be necessary to assess the biological and ecological effects the viruses have on their host. Due to the agricultural importance of this insect, the biological characterization of these viruses would give important information on the possibility to exploit viral entities as biological control agents. Finally, the presence of a such relevant number of viruses from a small population suggests a wide association between the brown marmorated stink bug and viral entities. Further studies to determine the possible exploitation of viral sequences to trace different populations are ongoing.

Olfactory responses of Trissolcus mitsukurii to plants attacked by target and non-target stink bugs suggest low risk for biological control.

In crop systems, successful management of invasive insect herbivores can be achieved through the introduction of exotic biocontrol agents, parasitoids or predators, having a coevolutionary history with the pest. To avert threats to local biodiversity, recent legislations require a risk assessment for the organism to be released. Evaluation of its ability to exploit, for host location, odours associated with target and non-target species is crucial for a better definition of its ecological host range. Using Y-tube olfactometer bioassays in a quarantine laboratory, we investigated the ability of the Asian egg parasitoid Trissolcus mitsukurii (Hymenoptera: Scelionidae) to exploit odours associated with the global invader Halyomorpha halys (Hemiptera: Pentatomidae) and with non-target stink bugs native to Southern Europe. We demonstrated that T. mitsukurii is attracted by plants exposed to feeding and egg deposition of the coevolved H. halys and the native Nezara viridula, while it is not attracted by physogastric (gravid) females or eggs alone. Remarkably, T. mitsukurii is repelled by plants bearing eggs of the beneficial Arma custos. Our results contribute to a more thorough and nuanced assessment of the potential non-target risks in the case of mass-release of parasitoids as part of a biological control programme for invasive stink bugs.

Implementing Mass Rearing of Trissolcus japonicus (Hymenoptera: Scelionidae) on Cold-Stored Host Eggs.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), a pest of Asian origin, has been causing severe damage to Italian agriculture. The application of classical biological control by the release of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), an exotic egg parasitoid, appears to be one promising solution. In Italy, releases of T. japonicus in the field were authorized in 2020. In this study, some parameters that could influence the rearing of T. japonicus in insectaries were investigated. A significantly higher production of progeny was observed on host eggs stored at 6 °C (86.5%) compared to -24 °C (48.8%) for up to two months prior to exposure to parasitism. There were no significant differences in progeny production from single females in a vial provided with only one egg mass (83.2%) or 10 females inside a cage with 6 egg masses (83.9%). The exposure of parasitoids to refrigerated (6 °C) egg masses of H. halys for 72 h led to a significantly higher production of progeny (62.1%) compared to shorter exposures for 48 (44.0%) or 24 h (37.1%). A decline in production of progeny by the same female was detected between the first (62.1%) and the second parasitization (41.3%). Adult parasitoids stored at 16 °C for up to 90 days had an 87.1% survival rate, but a significant decrease in progeny production was detected. These parameters could be adjusted when rearing T. japonicus for specific aims such as the production of individuals for field release or colony maintenance.

The complete mitochondrial genome of Trissolcus japonicus (Hymenoptera: Scelionidae), the candidate for the biological control of Halyomorpha halys (Hemiptera: Pentatomidae).

The samurai wasp Trissolcus japonicus (Ashmead, 1904) is a parasitoid hymenopteran that came into the limelight as the natural enemy of Halyomorpha halys. Here, we present the complete sequence of the mitochondrial genome of the CREATJ laboratory strain, naturally recovered in Italy in 2018. The molecule conforms to the typical model of animal mitochondrial genomes. Gene order is identical to that of its congeneric Trissolcus basalis. Phylogenetic analysis confirms its placement within monophyletic Scelionidae and Telenominae as the sister group of T. basalis.

Reproductive and Developmental Biology of Acroclisoides sinicus, a Hyperparasitoid of Scelionid Parasitoids.

Acroclisoides sinicus (Hymenoptera: Pteromalidae) was described in 1988 from China, but recent findings in Europe and North America within the framework of Halyomorpha halys (Hemiptera: Pentatomidae) biological control indicate a Holarctic distribution. The few records and fragmented information on A. sinicus are derived from generic observations of other species belonging to the same genus, and its biological and ethological traits are still completely unexplored. It was suspected to be a facultative or obligate hyperparasitoid of many egg parasitoid species (e.g., Scelionidae and Eupelmidae), especially those parasitizing Pentatomidae eggs. Laboratory colonies of A. sinicus were established from specimens collected in the field in Europe and the USA, which allowed us to investigate for the first time the life traits of this somewhat enigmatic species. Our studies confirmed the obligate hyperparasitoid hypothesis for species of Scelionidae but not of Eupelmidae. Laboratory studies revealed that A. sinicus is extremely selective in its host recognition as only the pupal stage of its host species is exploited for parasitization. Taking into consideration its hyperparasitoid habit, the adventive A. sinicus populations in Europe and North America may potentially be severe threats to pentatomid natural control as new components in the trophic chain of pentatomids and their parasitoid guilds.

Assessing the Distribution of Exotic Egg Parasitoids of Halyomorpha halys in Europe with a Large-Scale Monitoring Program.

The brown marmorated stink bug Halyomorpha halys is an invasive agricultural pest with a worldwide distribution. Classical biological control has been identified as the most promising method to reduce the populations of H. halys. Adventive populations of two candidates for releases, Trissolcus japonicus and Trissolcus mitsukurii, have recently been detected in Europe. To assess their distribution and abundance, a large-scale survey was performed. From May to September 2019, a wide area covering northern Italy and parts of Switzerland was surveyed, highlighting the expanding distribution of both Tr. japonicus and Tr. mitsukurii. Within four years after their first detection in Europe, both species have rapidly spread into all types of habitats where H. halys is present, showing a wide distribution and continuous expansion. Both exotic Trissolcus showed high levels of parasitism rate towards H. halys, while parasitization of non-target species was a rare event. The generalist Anastatus bifasciatus was the predominant native parasitoid of H. halys, while the emergence of native scelionids from H. halys eggs was rarely observed. The presence of the hyperparasitoid Acroclisoides sinicus was also recorded. This study provided fundamental data that supported the development of the first inoculative release program of Tr. japonicus in Europe.

Rearing Trissolcus japonicus and Trissolcus mitsukurii for Biological Control of Halyomorpha halys.

Halyomorpha halys is a severe agricultural pest of Asian origin that has invaded many countries throughout the world. Pesticides are currently the favored control methods, but as a consequence of their frequent use, often disrupt Integrated Pest Management. Biological control with egg parasitoids is seen as the most promising control method over the long-term. Knowledge of the reproductive biology under laboratory conditions of the most effective candidates (Trissolcus japonicus and Trissolcus mitsukurii) for optimizing production for field releases is strongly needed. Rearing of these egg parasitoids was tested by offering three different host supply regimes using new emerged females and aged, host-deprived females in different combinations. Results showed a mean progeny per female ranging from 80 to 85 specimens for T. japonicus and from 63 to 83 for T. mitsukurii. Sex ratios were strongly female biased in all combinations and emergence rates exceeded 94% overall. Cumulative curves showed that longer parasitization periods beyond 10-14 days (under the adopted rearing regimes) will not lead to a significantly increase in progeny production. However, ageing females accumulate eggs in their ovaries that can be quickly laid if a sufficient number of host eggs are supplied, thus optimizing host resources. Our data showed that offering H. halys egg masses to host-deprived female Trissolcus once a week for three weeks allowed its eggs to accumulate in the ovary, providing the greatest number of offspring within a three week span.

Long-lasting insecticide-treated nets: A new integrated pest management approach for Popillia japonica (Coleoptera: Scarabaeidae).

The Japanese beetle Popillia japonica Newman is a US and EU quarantine insect pest that has recently invaded northern Italy. Its ability to rapidly spread in new areas makes this insect a threat to agriculture. In the last decades, several trials on biological control of the Japanese beetle by entomopathogenic nematodes and fungi have been carried out with variable efficacy. However, the necessity of an integrated pest management approach to improve control has arisen. Long-lasting insecticide-treated nets (LLINs) have been used to control other agricultural pests with an attract-and-kill strategy. Here, we present results from laboratory evaluation of 2 LLINs, Storanet® (BASF™) and ZeroFly® (Vestergaard™), against P. japonica adults. Both were effective in killing the beetles; however, some differences emerged if different exposure times were compared: ZeroFly® always gave 100% mortality in tests from 5-s to 30-min exposure; Storanet® showed 100% mortality only with 30-min exposure and going down to 89%-99% mortality for 5-s to 15-min exposure. A description of the paralysis process occurring at 5-s exposure is given. Possible field application of LLINs within programs of integrated pest management is discussed. Integr Environ Assess Manag 2019;15:259-265. © 2018 SETAC.

Managing outbreaks of the citrus long-horned beetle Anoplophora chinensis (Forster) in Europe: molecular diagnosis of plant infestation.

BACKGROUND: Anoplophora chinensis (Forster) (Coleoptera Cerambycidae) is a polyphagous long-horned beetle native to Eastern Asia that infests a wide range of broadleaved plants, causing disruption of vascular tissue, structural weakness and tree death. As a result, A. chinensis is a quarantine pest for the European Union. In order to confirm its infestations on plants, it is necessary to obtain adult or larval specimens on which morphological or molecular analysis can be performed. However, obtaining such specimens from infested plants can be a demanding and difficult task. Therefore, a diagnostic tool that is non-invasive for the plant and able to be performed in the absence of any insect stages may be useful to confirm infestations of A. chinensis on plants. RESULTS: A protocol is presented that is based on polymerase chain reaction amplification using DNA extracted from A. chinensis faecal material collected in the field. CONCLUSION: Results obtained in the present work show that the non-invasive approach is a reliable and accurate alternative diagnostic tool in phytosanitary surveys.