On the distribution and establishment of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) in Germany

Die invasive Marmorierte Baumwanze, Halyomorpha halys, verursacht weltweit wirtschaftliche Schäden in Obst- und Gemüsekulturen. Darüber hinaus ist sie ein Lästling, der gerne in großer Anzahl in menschlichen Behausungen überwintert. In den Ursprungsgebieten Ostasiens wird diese Schadwanze durch natürliche Gegenspieler reguliert. Die Schlupfwespe Trissolcus japonicus ist durch sehr hohe Parasitierungsraten der Eigelege ein dominanter Antagonist von H. halys. Adventive Populationen von T. japonicus wurden bereits in Nordamerika und mehreren Ländern Europas nachgewiesen, wo sie sich im Ausbreitungsgebiet von H. halys erfolgreich etabliert haben. In dieser Studie werden die Ergebnisse eines Monitorings von H. halys-Eigelegen zur Ausbreitung und Etablierung der Schlupfwespe dargestellt. In Deutschland erfolgte der Erstfund von T. japonicus im Jahr 2020 an drei Standorten in Baden-Württemberg. Seither haben sich weitere Fundorte innerhalb Baden-Württembergs sowie in Hessen, Rheinland-Pfalz, Bayern und Nordrhein-Westfalen ergeben. T. japonicus kann nachweislich erfolgreich unter den klimatischen Bedingungen in Baden-Württemberg überwintern, sich fortpflanzen und innerhalb des Verbreitungsgebietes von H. halys ausbreiten. Der aktuelle Status von T. japonicus wird dargestellt.The invasive brown marmorated stink bug, Halyomorpha halys, is an economically important pest of fruit and vegetable crops. It is also a nuisance pest overwintering in large numbers in man-made structures. In its native range, natural biological control plays a key role in regulating this pest. The egg parasitoid Trissolcus japonicus is a dominant natural enemy showing high parasitism rates on H. halys eggs. Adventive populations of T. japonicus have been reported from North America and several European countries with successful establishment within the new distribution areas of H. halys. The object of this study was to monitor H. halys egg masses to assess the distribution and establishment of T. japonicus. In Germany, T. japonicus was first reported in 2020 at three sites in Baden-Wuerttemberg. Since then, additional locations have been confirmed in Hesse, Rhineland-Palatinate, Bavaria, and North Rhine-Westphalia. Thus, T. japonicus has been able to successfully overwinter, reproduce, and spread within H. halys’ distribution range in Baden-Wuerttemberg. Here, the current status of presence and establishment of T. japonicus in Germany is reported

Selected invasive pests in fruiticulture – overview of the current situation and ongoing research projects on spotted wing drosophila and stink bugs

Gebietsfremde invasive Schadinsekten haben im Obstbau im vergangenen Jahrzehnt große wirtschaftliche Schäden verursacht und den kommerziellen Obstanbau vor neue Herausforderungen gestellt. Die Gründe für die Ausbreitung dieser Insekten sind vielfältig. Regulierungsmaßnahmen zur Eindämmung dieser Neozoen benötigen Erfahrungen in verschiedenen Kulturpflanzen und umfangreiche Kenntnisse zum Verhalten der invasiven Arten. Für die Kirschessigfliege gibt es bereits erste wirksame Regulierungsstrategien, sowie eine Dekade an Erfahrung und somit umfangreiches Wissen zur Biologie, Ökologie und Genetik dieses Schadinsekts, welches für die Weiterentwicklung von Bekämpfungsmaßnahmen unabdingbar ist. Invasive Schadwanzen werden derzeit an verschiedenen Standorten intensiv untersucht. Potenziell wirksame, alternative Methoden zur Regulierung werden aktuell in Forschungsprojekten erarbeitet.Foreign invasive species have caused considerable economic damage in fruiticulture during the past decade. Consequently, commercial fruit production is facing major, new challenges. Reasons for the spread of those pest insects are manifold. Appropriate control measures for the containment of invasive species depend on several years of experience with diverse fruit cultures and in-depth-knowledge of the insects´ behaviour. For Spotted Wing Drosophila, first efficient mechanisms for the control of fruit infestation were identified and are in use. Moreover, broad knowledge of biology, ecology, and genetics of this species is available and can be applied for the development of further control strategies. Research on invasive stink bugs is currently undertaken at different locations. Effective means for their population regulation are developed in those research projects

Egg load dynamics and the risk of egg and time limitation experienced by an aphid parasitoid in the field

Insect parasitoids and herbivores must balance the risk of egg limitation and time limitation in order to maximize reproductive success. Egg and time limitation are mediated by oviposition and egg maturation rates as well as by starvation risk and other determinants of adult lifespan. Here, we assessed egg load and nutritional state in the soybean aphid parasitoid Binodoxys communis under field conditions to estimate its risk of becoming either egg- or time-limited. The majority of female B. communis showed no signs of egg limitation. Experimental field manipulations of B. communis females suggested that an average of 4–8 eggs were matured per hour over the course of a day. Regardless, egg loads remained constant over the course of the day at approximately 80 eggs, suggesting that egg maturation compensates for oviposition. This is the first case of such “egg load buffering” documented for a parasitoid in the field. Despite this buffering, egg loads dropped slightly with increasing host (aphid) density. This suggests that egg limitation could occur at very high host densities as experienced in outbreak years in some locations in the Midwestern USA. Biochemical analyses of sugar profiles showed that parasitoids fed upon sugar in the field at a remarkably high rate. Time limitation through starvation thus seems to be very low and aphid honeydew is most likely a source of dietary sugar for these parasitoids. This latter supposition is supported by the fact that body sugar levels increase with host (aphid) density. Together, these results suggest that fecundity of B. communis benefits from both dynamic egg maturation strategies and sugar-feeding

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

Trissolcus japonicus (Ashmead) (Hymenoptera, Scelionidae) emerges in North America

Trissolcus japonicus (Ashmead) is an Asian egg parasitoid of the brown marmorated stink bug, Halyomorpha halys (Stål). It has been under study in U.S. quarantine facilities since 2007 to evaluate its efficacy as a candidate classical biological control agent and its host specificity with regard to the pentatomid fauna native to the United States. A survey of resident egg parasitoids conducted in 2014 with sentinel egg masses of H. halys revealed that T. japonicus was already present in the wild in Beltsville, MD. Seven parasitized egg masses were recovered, of which six yielded live T. japonicus adults. All of these were in a wooded habitat, whereas egg masses placed in nearby soybean fields and an abandoned apple orchard showed no T. japonicus parasitism. How T. japonicus came to that site is unknown and presumed accidental

Indigenous arthropod natural enemies of the invasive brown marmorated stink bug in North America and Europe

Since the establishment of the brown marmorated stink bug, Halyomorpha halys (St\ue5l) (Hemiptera: Pentatomidae) in North America and Europe, there has been a large, multi-group effort to characterize the composition and impact of the indigenous community of arthropod natural enemies attacking this invasive pest. In this review, we combine 98 indigenous natural enemy datasets spanning a variety of sampling methods, habitats, and geographic areas. To date, the vast majority of H. halys biological control research has focused on the egg stage, using sentinel egg masses to characterize indigenous parasitoid and predator communities and their contribution to H. halys egg mortality. Although egg parasitism and predation levels by indigenous natural enemies are low (typically <10% each) in most surveys, total egg mortality attributable to natural enemies can be higher (typically between 5 and 25%; up to 83%)\u2014even though these values were likely underestimated in most cases because some mortality due to biological control was not recognized. In North America, where the most data are available, it appears that the relative prevalence of different indigenous parasitoid species varies among habitat types, particularly between crop and non-crop habitats. Predator species responsible for egg mortality are much less commonly identified, but appear to include a wide variety of generalist chewing and sucking predators. To date, studies of natural enemies attacking H. halys nymphs and adults are relatively rare. Based on our review, we identify a number of key research gaps and suggest several directions for future research