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The invasive, Halyomorpha halys (Hemiptera: Pentatomidae), is a severe economic insect pest native to East Asia. A strong effort has been made to identify natural egg parasitoids of H. halys in invaded regions, but parasitism rates reported from these studies have been inconsequentially low. To determine the species composition, phenology, and efficiency of egg parasitoids in the native region of H. halys, we deployed fresh and frozen sentinel H. halys egg masses from March through December in Kyoto, Japan. Our findings provide valuable insights on the abundance and parasitism rates of native H. halys parasitoids in Japan. A total of seven parasitoid species emerged from the sentinel egg masses, but Trissolcus japonicus had the highest parasitism rate of all parasitoids recovered (84% on fresh egg masses) and maintained the largest portion of the total parasitoid species composition (60% on fresh egg masses). The early season parasitoid community in Kyoto, Japan, is dominated by T. japonicus, with the first parasitism activity occurring in March. Throughout the course of the field study, T. japonicus also sustained a significantly higher parasitism rate on fresh H. halys eggs than frozen. The results from this research help expand the understanding of parasitoids in the native region of H. halys and hold importance for the future development of biological control programs against this invasive pest.

BACKGROUND In order to better understand the population dynamics of invasive species in their native range, we developed two predictive phenological models using the ubiquitous invasive insect pest, Halyomorpha halys (Stal) (Hemiptera: Pentatomidae), as the model organism. Our work establishes a zero-inflated negative binomial regression (ZINB) model, and a general additive mixed model (GAMM) based on 11 years of black light trap monitoring of H. halys at three locations in Japan. RESULTS The ZINB model indicated that degree days (DD) have a significant effect on the trap catch of adult H. halys, and that precipitation has no effect. A dataset generated by 1000 simulations from the ZINB suggested that higher predicted trap catches equated to a lower probability of encountering a zero-count. The GAMM produced a cubic regression smooth curve which forecasts the seasonal phenology of H. halys as following a bell-shaped trend in Japan. Critical DD points during the field season in Japan included 261 DD for first H. halys adult detection and 1091 DD for peak activity. CONCLUSIONS This study establishes the first models capable of forecasting native H. halys population dynamics based on DD. These robust models practically improve population forecasting of H. halys in the future and help fill gaps in knowledge pertaining to its native phenology, thus ultimately contributing to the progression of efficient management of this globally invasive species. © 2021 Society of Chemical Industry.

The invasive vinegar fly, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is a major economic pest of soft-skinned fruit in the USA. In order to identify suitable biological control agents in Wisconsin, we assessed the presence and impact of potential natural enemies of D. suzukii in tart cherry and raspberry farms with documented D. suzukii populations. Yellow sticky cards and sentinel traps baited with D. suzukii or D. melanogaster larvae and pupae were deployed in these agricultural areas in the foliage and near the soil surface. Four families of parasitoids with known species that successfully parasitize D. suzukii (Pteromalidae, Braconidae, Figitidae, and Diapriidae) were found on sticky traps at all sampling sites. However, no parasitoids emerged from D. suzukii or D. melanogaster sentinel larvae or pupae throughout the duration of the field assessment. Predation was documented on sentinel D. suzukii pupae (1–4%) and sentinel D. melanogaster pupae (5–8%). The majority of sentinel pupae never emerged upon their return from the field and showed no evidence of field predation. Between 70 and 92% of recovered D. suzukii pupae were dead, and 46–72% of D. melanogaster pupae were dead. The absence of parasitoids found emerging from the sentinel drosophilid larvae and pupae and overall low levels of predation suggests that native biological control may provide limited potential as a management option against D. suzukii in Wisconsin at this time.

Brown marmorated stinkbug (BMSB), Halyomorpha halys Stal (Hemiptera: Pentatomidae), is native to Asia and an invasive urban and agricultural pest in the US. In California (CA), BMSB has been recorded attacking specialty crops such as almonds and peaches. The egg parasitoid Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), a key BMSB natural enemy native to Asia, is a candidate for classical biological control efforts targeting BMSB in CA and other parts of the US Trissolcus japonicus cannot be introduced deliberately into CA for BMSB control without US federal regulatory agency approval which is contingent on better understanding of its host range and specificity. Consequently, the host specificity and physiological host range of T. japonicus was evaluated under laboratory quarantine conditions by exposing eggs of BMSB and non-target pentatomid hosts (native and other exotic species) found in CA to T. japonicus. No-choice and binary-choice experiments provided female T. japonicus with equal unrestricted access to eggs of BMSB and non-target pentatomids. In addition to BMSB, eggs from six of ten resident pentatomid species found in CA were parasitized by T. japonicus. However, T. japonicus attack and emergence rates were consistently higher on BMSB when compared to non-target species. These results suggest that T. japonicus is oligophagous, but BMSB is a superior reproductive host compared to non-target pentatomid species that were evaluated. The implications of these findings for classical biological control efforts targeting BMSB in CA are discussed.

Here we assessed population dynamics, natural enemy fauna (with emphasis on egg parasitoid), and population genetic structure (based on mitochondrial DNA) of the invasive litchi stink bug (LSB), Tessaratoma papillosa in Taiwan. Our major findings include: (1) fluctuations of LSB in numbers of adults, mating pairs, and egg masses over a 2-year period in Taiwan generally resemble those in the native populations; (2) Anastatus dexingensis and A. fulloi are among the most dominant LSB egg parasitoids, with the former consistently outnumbering the latter throughout Taiwan; (3) the presence of two genetically distinct clades suggests LSB in Taiwan most likely derived from multiple invasions. All these data practically improve our understanding of this invasive insect pest, particularly its ecological and genetic characteristics in the introduced area, which represents critical baseline information for the design of future integrated pest management strategies.

Drosophila suzukii (Matsumura) is an invasive species of vinegar fly that infests soft-skinned and stone fruits. Since its first detection in the United States, D. suzukii has become a prominent economic threat in fruit crop industries, particularly affecting caneberry and sweet cherry growers. This study examined the susceptibility of tart cherries (Prunus cerasus) to D. suzukii and sampled for larvae and adult D. suzukii during the tart cherry growing season. Four tart cherry cultivars (Montmorency, Balaton, Carmine Jewel, and Kántorjánosi) were tested at three different ripeness stages (unripe, ripening, and ripe), in no-choice laboratory bio-assays. Field monitoring and sampling revealed that first adult D. suzukii detection occurred on 16 June, and first field larval D. suzukii detection occurred on 28 July. Adult D. suzukii populations increased through late August, and high numbers of adults overlapped with the tart cherry harvest. Lab assays indicated that tart cherry cultivars generally became more susceptible to D. suzukii as they ripened. As the fruit developed, °Brix (sugar content) increased and firmness generally decreased. Tart cherry °Brix and firmness were not correlated with the number of D. suzukii eggs per gram of fruit, but showed a significant interaction effect with the number of larvae and adults per gram of fruit. This study shows that tart cherries are largely not susceptible to D. suzukii when unripe and become susceptible as soon as the fruits change color, suggesting that fruits should be protected as soon as they begin to ripen and D. suzukii populations begin to rise.

Halyomorpha halys (Hemiptera: Pentatomidae) is an invasive pest native to Asia that causes severe economic losses in agriculture around the world. Although chemical control is relied upon for control of this pest, better long-term solutions are needed to achieve sustainable control. Currently, information is scarce on the complex of predators regulating populations of H. halys in its native region. Through laboratory bio-assays, we investigated the predatory ability of two species of acrobat ant native to Japan, Crematogaster matsumurai and C. osakensis, and the invasive Argentine ant, Linepithema humile, presented with different immature life stages of H. halys. Results indicated that these Japanese Crematogaster ants did not prey on the H. halys eggs or affect their eclosion, but did reduce the survival of early (first, second, and third) instar nymphs. Crematogaster matsumurai limited the survival of first, second, and third instar nymphs to 0%, 40%, and 73% respectively, and C. osakensis reduced their survival to 0%, 13%, and 60%, respectively. Predation of immature H. halys by L. humile reduced the survival of all instars to zero under the laboratory conditions. These data suggest that generalist Japanese Crematogaster ants may play an important role in reducing immature survival of H. halys in their native range, but likely act additively with other natural enemies that inflict mortality on different life stages. This work demonstrates that ants deserve consideration in the development of integrated pest management strategies for H. halys.

In the United States, California (CA) is the primary commercial producer of pistachio nuts, Pistacia vera L. (Anacardiaceae). The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), an invasive and polyphagous insect pest from Asia, has established in urban areas in several pistachio-growing counties in CA. Breeding BMSB populations have not been detected in commercial pistachio acreage. However, the detection of BMSB in Kern and Fresno counties, major Kerman pistachio producing areas in CA, underscored key knowledge gaps on BMSB ecology in CA and motivated investigations on the susceptibility of pistachio nuts to BMSB feeding. Laboratory feeding trials conducted in quarantine under permit indicated that adult BMSB stylets can penetrate developing pistachio shells and associated feeding was correlated with kernel necrosis for nuts collected mid to late season (June to August 2016). Feeding damage estimates indicated that higher levels of kernel injury were associated with female BMSB when compared to feeding by male BMSB. These results suggest that there is probable risk of feeding damage to field grown pistachios from BMSB. The implications of this study for BMSB pest management in the CA pistachio system and future research directions are discussed.