Efficacy of Kairomone Lures to Attract Parasitoids of Halyomorpha halys

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.

Evaluating invasion risk and population dynamics of the brown marmorated stink bug across the contiguous United States

BACKGROUND

Invasive species threaten the productivity and stability of natural and managed ecosystems. Predicting the spread of invaders, which can aid in early mitigation efforts, is a major challenge, especially in the face of climate change. While ecological niche models are effective tools to assess habitat suitability for invaders, such models have rarely been created for invasive pest species with rapidly expanding ranges. Here, we leveraged a national monitoring effort from 543 sites over 3 years to assess factors mediating the occurrence and abundance of brown marmorated stink bug (BMSB, Halyomorpha halys), an invasive insect pest that has readily established throughout much of the United States.

RESULTS

We used maximum entropy models to estimate the suitable habitat of BMSB under several climate scenarios, and generalized boosted models to assess environmental factors that regulated BMSB abundance. Our models captured BMSB distribution and abundance with high accuracy, and predicted a 70% increase in suitable habitat under future climate scenarios. However, environmental factors that mediated the geographical distribution of BMSB were different from those driving abundance. While BMSB occurrence was most affected by winter precipitation and proximity to populated areas, BMSB abundance was influenced most strongly by evapotranspiration and solar photoperiod.

CONCLUSION

Our results suggest that linking models of establishment (occurrence) and population dynamics (abundance) offers a more effective way to forecast the spread and impact of BMSB and other invasive species than simply occurrence-based models, allowing for targeted mitigation efforts. Implications of distribution shifts under climate change are discussed. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Captive Rearing Success and Critical Thermal Maxima of Bombus griseocollis (Hymenoptera: Apidae): A Candidate for Commercialization?

Commercialized bumble bees (Bombus) are primary pollinators of several crops within open field and greenhouse settings. However, the common eastern bumble bee (Bombus impatiens Cresson, 1863) is the only species widely available for purchase in North America. As an eastern species, concerns have been expressed over their transportation outside of their native range. Therefore, there is a need to identify regionally appropriate candidates for commercial crop pollination services, especially in the western U.S.A. In this study, we evaluated the commercialization potential of brown-belted bumble bees (Bombus griseocollis De Geer, 1773), a broadly distributed species throughout the U.S.A., by assessing nest initiation and establishment rates of colonies produced from wild-caught gynes, creating a timeline of colony development, and identifying lab-reared workers' critical thermal maxima (CTMax) and lethal temperature (ecological death). From 2019 to 2021, 70.6% of the wild-caught B. griseocollis gynes produced brood in a laboratory setting. Of these successfully initiated nests, 74.8% successfully established a nest (produced a worker), providing guidance for future rearing efforts. Additionally, lab-reared workers produced from wild-caught B. griseocollis gynes had an average CTMax of 43.5°C and an average lethal temperature of 46.4°C, suggesting B. griseocollis can withstand temperatures well above those commonly found in open field and greenhouse settings. Overall, B. griseocollis should continue to be evaluated for commercial purposes throughout the U.S.A.

Comparison of Yellow and Blue Sticky Cards for Detection and Monitoring Parasitoid Wasps of the Invasive Halyomorpha halys (Hemiptera: Pentatomidae)

The invasive Halyomorpha halys (Stål) is a significant agricultural and urban nuisance pest in many parts of the world. In North America, biological control of H. halys by parasitoid wasps in the families Scelionidae and Eupelmidae has shown promise. An effective technique for detection and monitoring native and exotic parasitoids is the deployment of yellow sticky cards; however, yellow cards also attract nontarget arthropods, reducing efficiency and accuracy of parasitoid screening. This study sought to identify an alternative yet effective trapping technique by comparing the number of target parasitoid wasps [Anastatus spp. Motschulsky (Hymenoptera: Eupelmidae), Telenomus spp. Haliday (Hymenoptera: Scelionidae), and Trissolcus spp. Ashmead (Hymenoptera: Scelionidae)] and arthropod bycatch on yellow and blue sticky cards deployed in urban, orchard, and vegetable landscapes in northern Utah from late May to early October in 2019 and 2020. Yellow sticky cards captured 54-72% more target parasitoids than blue cards from June through August in all three landscape types in both years; however, a positive correlation in parasitoid capture indicated blue cards detect target parasitoids, just in fewer numbers. Both card colors detected adventive Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) in initial findings of 2019, and in expanded locations of 2020. Furthermore, blue cards captured 31-48% less Diptera and nontarget Hymenoptera than yellow cards in both years across all three landscapes, translating to reduced card processing time and impacts to beneficial insect populations. Our results suggest that blue vs yellow sticky cards offer an alternative monitoring technique to survey for H. halys parasitoids.

Urban host plant utilisation by the invasive Halyomorpha halys (Stål) (Hemiptera, Pentatomidae) in northern Utah

The invasive and highly polyphagous brown marmorated stink bug, Halyomorpha halys (Stål), is a severe agricultural and urban nuisance pest in North America. Since its initial invasion into Utah in 2012, H. halys has become well established in urban and suburban locations along the western foothills of the Wasatch Front in northern Utah. Bordering the Great Basin Desert, this area is unique from other North American locations with H. halys due to its high elevation (> 1200 m), aridity (30-year mean RH = 53.1%; dew point = -1.9 °C) and extreme temperatures (the 30-year mean minimum and maximum in January and July in Salt Lake City range from -3.1 to 3.6 °C and 20.3 to 32.4 °C, respectively). To document which plant species harbour H. halys, surveys were conducted in 17 urban/suburban sites in four counties during 2017 and 2018. Halyomorpha halys was more abundant in Salt Lake and Utah counties than in the more northern counties of Davis and Weber and was found on 53 plant species, nine of which hosted two or more developmental stages in both years. The majority of hosts were in the families Fabaceae, Rosaceae and Sapindaceae. Northern catalpa, Catalpa speciosa (Warder), was the most consistent host, supporting a majority of H. halys detections in all life stages; thus we identify it as a sentinel host. Twenty-nine species were novel hosts for H. halys in North America; of these, Acer ginnala Maxim, Populus tremuloides Michx., Prunus armeniaca × domestica ‘Flavor King’ and Prunus virginiana ‘Schubert’ were detected with two or more life stages of H. halys in both years. Peak populations of H. halys occurred from mid-June to mid-September. We describe H. halys plant utilisation by life stage and seasonal period to aid future detection and management of this invasive insect in the greater Intermountain West region.

Impact of Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) Feeding on Tart Cherry (Rosales: Rosaceae) Quality and Yield in Utah

Brown marmorated stink bug (Halyomorpha halys Stål) is an invasive and economically important agricultural and ornamental insect pest now established in 46 U.S. states. It was first detected in Utah in 2012 and began causing agricultural damage in 2017. Tart cherry (Prunus cerasus Linnaeus) is a major processed agricultural commodity in Utah; yet, its susceptibility to brown marmorated stink bug is unstudied. Limb cages with six brown marmorated stink bug adults, nymphs, or no brown marmorated stink bug were established in a randomized complete block design in a tart cherry orchard to determine feeding impact on different fruit developmental stages. After 1 wk of feeding, half of the fruits in each cage were removed to assess feeding intensity, and the remainder left through maturity to assess marketability and quality. Feeding by adults and nymphs between petal fall and fruit pit hardening, even at feeding pressures as low as 1.7-4.0 feeding sites per fruit, caused 100% abscission of fruits, significantly reducing marketability when compared with the control treatment. For fruits that escaped abscission and matured, few quality differences were detected among treatments, indicating that brown marmorated stink bug feeding caused minimal detectable quality loss to this processed tree fruit crop. We conclude that tart cherries are at risk of abscission with short-term brown marmorated stink bug feeding between petal fall and pit hardening when overwintered adults or F1 nymphs are present in orchards, and suggest that longer-term feeding may be necessary to cause quality and yield reductions after pit hardening.

Surveys in northern Utah for egg parasitoids of Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) detect Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae)

The highly polyphagous and invasive brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), has become a significant insect pest in North America since its detection in 1996. It was first documented in northern Utah in 2012 and reports of urban nuisance problems and plant damage have since increased. Biological control is the preferred solution to managing H. halys in North America and other invaded regions due to its alignment with integrated pest management and sustainable practices. Native and non-native biological control agents, namely parasitoid wasps, have been assessed for efficacy. Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) is an effective egg parasitoid of H. halys in its native range of southeast Asia and has recently been documented parasitising H. halys eggs in North America and Europe. Field surveys for native and exotic egg parasitoids using wild (in situ) and lab-reared H. halys egg masses were conducted in suburban and agricultural sites in northern Utah from June to September 2017-2019. Seven native wasp species in the families Eupelmidae and Scelionidae were discovered guarding H. halys eggs and adult wasps from five of these species completed emergence. Native species had low mean rates of adult emergence from wild (0.5-3.7%) and lab-reared (0-0.4%) egg masses. In 2019, an adventive population of T. japonicus was discovered for the first time in Utah, emerging from 21 of the 106 wild H. halys egg masses found that year, and none from lab-reared eggs. All T. japonicus emerged from egg masses collected on Catalpa speciosa (Warder). Our results support other studies that have observed biological control of H. halys from T. japonicus and improved parasitoid wasp detection with wild as compared to lab-reared H. halys egg masses.

Season-Long Monitoring of the Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) Throughout the United States Using Commercially Available Traps and Lures

Reliable monitoring of the invasive Halyomorpha halys abundance, phenology and geographic distribution is critical for its management. Halyomorpha halys adult and nymphal captures on clear sticky traps and in black pyramid traps were compared in 18 states across the Great Lakes, Mid-Atlantic, Southeast, Pacific Northwest and Western regions of the United States. Traps were baited with commercial lures containing the H. halys pheromone and synergist, and deployed at field sites bordering agricultural or urban locations with H. halys host plants. Nymphal and adult captures in pyramid traps were greater than those on sticky traps, but captures were positively correlated between the two trap types within each region and during the early-, mid- and late season across all sites. Sites were further classified as having a low, moderate or high relative H. halys density and again showed positive correlations between captures for the two trap types for nymphs and adults. Among regions, the greatest adult captures were recorded in the Southeast and Mid-Atlantic on pyramid and sticky traps, respectively, with lowest captures recorded in the West. Nymphal captures, while lower than adult captures, were greatest in the Southeast and lowest in the West. Nymphal and adult captures were, generally, greatest during July-August and September-October, respectively. Trapping data were compared with available phenological models showing comparable population peaks at most locations. Results demonstrated that sticky traps offer a simpler alternative to pyramid traps, but both can be reliable tools to monitor H. halys in different geographical locations with varying population densities throughout the season.

Pheromone Lure and Trap Color Affects Bycatch in Agricultural Landscapes of Utah

Aerial traps, using combinations of color and attractive lures, are a critical tool for detecting and managing insect pest populations. Yet, despite improvements in trap efficacy, collection of nontarget species ("bycatch") plagues many insect pest surveys. Bycatch can influence survey effectiveness by reducing the available space for target species and increasing trap screening time, especially in areas where thousands of insects are captured as bycatch in a given season. Additionally, bycatch may negatively impact local nontarget insect populations, including beneficial predators and pollinators. Here, we tested the effect of pheromone lures on bycatch rates of Coccinellidae (Coleoptera), Apoidea (Hymenoptera), and nontarget Lepidoptera. Multicolored (primarily yellow and white) bucket traps containing a pheromone lure for capturing one of three survey target species, Spodoptera litura (F.), S. littoralis (Boisduval), or Helicoverpa armigera (Hübner), were placed in alfalfa and corn fields, and compared to multicolored traps without a pheromone lure. All-green traps with and without H. armigera lures were employed in a parallel study investigating the effect of lure and trap color on bycatch. Over 2,600 Coccinellidae representing seven species, nearly 6,400 bees in 57 species, and >9,000 nontarget moths in 17 genera were captured across 180 traps and seven temporal sampling events. Significant effects of lure and color were observed for multiple taxa. In general, nontarget insects were attracted to the H. armigera lure and multicolored trap, but further studies of trap color and pheromone lure specificity are needed to better understand these interactions and to minimize nontarget captures.