Research Project: Biology, Ecology, Genetics, and Genomics of Introduced Species for Biological Control of Invasive and Other Insect Pests

Location: Beneficial Insects Introduction Research Unit

2022 Annual Report

Objectives
Objective 1: Investigate key biotic factors influencing the spatial and temporal dynamics of wood-boring pest (including ALB and EAB) populations in their native range, focusing on exploration and quarantine service for effective, host-specific natural enemies (parasitoids) for biocontrol. Subobjective 1a - Explore for parasitoids of ALB and EAB in the pests’ native range (Asia). Subobjective 1b - Evaluate the role of the key natural enemies in regulating the spatial and temporal dynamics of ALB and EAB in the area of collection in Asia. Subobjective 1c - Evaluate the host specificity of parasitoids discovered for introduction to North America for ALB and EAB control. Subobjective 1d - Quarantine services to support research on exotic insect pests and their natural enemies. Objective 2: Conduct field releases and evaluate impacts of extant (indigenous) and previously introduced parasitoids on populations of wood-boring beetles such as EAB and ALB in the United States, while elucidating factors that influence successful establishment of introduced biological control agents, such as climate adaptation, release methodology, genetic variation in founder populations and risk-spreading (diapause) strategy. Objective 3: For newly discovered parasitoids of ALB, EAB and other invasive pests, and based on studies of life histories and reproductive biology, develop effective rearing technologies for these natural enemies, focusing on optimizing host stage, host substrate complex, temperature, photoperiod and relative humidity. Subobjective 3a - Characterize the reproductive biology, risk-spreading (diapause) strategy and key life history parameters of most promising parasitoid species. Subobjective 3b - Determine the optimal host stage and host-substrate complex in association with host density and host-to-parasitoid ratio. Subobjective 3c - Determine the optimal environmental conditions for adult parasitoid survival, oviposition and progeny development including diapause induction and termination.

Approach
Using the approaches relevant to the knowledge base of the targeted pests and their natural enemies, we will conduct foreign explorations for new natural enemies from the pests’ native home (Northeast Asia) and construct life tables of the target pest populations to evaluate the impact of the natural enemies on the pests’ population dynamics in Northeast Asia. After selecting the most promising (or efficient) natural enemies, we will test the selected natural enemies against non-target wood-boring insects in North America to delineate their host range for biological control introduction against the target pests. Upon regulatory approval for environmental releases of the discovered natural enemies in North America, we will conduct field experiments to assess their establishment, dispersal and impacts on the target pests’ population in the U.S. Laboratory studies will also be conducted to collect information on the parasitoid’s biology, risk-spreading and reproductive strategy and life history and to develop efficient rearing methods for mass-production of the introduced natural enemies for biological control releases. In addition, this project will provide quarantine services, host range data and mass-rearing technologies for natural enemies of high priority plant pests to state and federal agencies.

Progress Report
COVID-19 pandemic continued affecting our laboratory and field experiments planned for the fall of 2021 and spring of 2022. Our field work on foreign exploration for natural enemies of Asian longhorned beetle (ALB), Emerald ash borer (EAB), and Spotted lantern fly (SLF) in South Korea, China and other parts of Asia were halted due to COVID-19 pandemic restrictions of international travels until the recent openings for international travel by the agency. With the lifting of COVID-19 safety drawdown, however, we managed to either substantially or fully meet the 24-month milestones in accomplishing portions of objectives for ALB, EAB and SLF research. Detailed progress is described below: ALB RESEARCH: Surveys for ALB parasitoids were conducted during 2021 by our collaborators at the Chinese Academy of Forestry and Seoul National University. In China, surveys were conducted in Zunyi (Guizhou), Kunming (Yunnan), Shanghai, and Beijing, from June to September 2021. A total of 264, 10, 62, and 68 sentinel ALB logs were deployed in 18 sites in Zunyi, two sites in Kunming, four sites in Beijing, and two sites in Shanghai, respectively. Two major parasitoids (Spathius anoplophorae and Oxysychus glabripennisi) were found in all four locations, where total parasitism varied from 0 to 14.4%. For the first time, these two parasitoids were found in Kunming. In South Korea, surveys were conducted in natural forests (in Gapyeong) using sentinel logs specifically designed to discover egg parasitoids. In total, 258 logs were launched at three sites in July and August 2021. One larval parasitoid (Spathius sp.) was found to attack ALB in early larval stage, but no egg parasitoid was found. We also launched a Malaise trap near where an egg parasitoid was collected in 2019. Seven putative egg parasitoid samples were sequenced, but these sequences did not match the ALB egg parasitoid sequence. The major parasitoid (S. anoplophorae) found in China has been imported into Beneficial Insects Introduction Unit (BIIRU) and successfully reared for over 30 generations. Various aspects of the parasitoid’s reproductive biology (egg maturation dynamics, life-time fecundity, host stage preference), developmental time, and other life-history traits (clutch size and offspring sex ratio) have been investigated. We are currently evaluating its host specificity. Results from these field surveys and laboratory testing will be written up for publications in FY23-24. With the collaboration from APHIS and University of Massachusetts, we conducted field releases of a North American parasitoid Ontsira mellipes from June to September 2021 and then deployed sentinel host larval logs to estimate its efficacy against ALB larvae in the quarantine zone in Worcester, MA (with all appropriate federal and state permits and permission to move regulated articles). In total, 144 logs were launched, and 3179 females were released. Three larvae were parasitized by O. mellipes. We suspected that the low parasitism was possibly because the wasps dispersed away from the released trees when being released. Improved release methods by placing host logs containing parasitoid cocoons (which allows the wasps to emerge and disperse naturally) are being used for this summer’s trials. To determine effects of the lethal dsRNA (dsIAP) via trophic exposures, maple sticks freshly cut from dsRNA-injected maple trees were exposed to ALB adults for 10 days, which resulted in higher mortality (70%) of exposed beetles than that (50%) from the control maple sticks (treated with dsGFP). In addition, we also evaluated direct effects on adult wasp’s survival via injection of dsIAP formulation, and indirect effects on the detectability and suitability of host larvae treated with different doses of dsIAP formulation. No direct effect was detected on the adult wasp survival, but indirect effects may occur when the wasp attacks dsRNA-affected ALB larvae, and wasp offspring failed to develop on ALB larvae treated with high doses of dsRNA (# 395397). EAB RESEARCH: With the help from several university and local state cooperators, we continued field evaluations of the establishment, persistence, and impact of previously introduced biocontrol agents (egg and larval parasitoids) in mid-Atlantic (Maryland and Delaware), Midwest (Michigan) and Northeast (Massachusetts, New York, and Connecticut) of the U.S. on the emerald ash borer (Agrilus planipennisi). Findings from these field studies showed the successful establishment and persistence of the newly introduced larval parasitoid (Spathius galinae) along with the earlier introduced agent (Tetrastichus planipennisi). Although our 2020 fall survey showed the significant suppression of emerald ash borer population growth by S. galinae (# 384956) in both Midwest and Northeast, our recent data (collected from the fall of 2021 and spring of 2022) indicated a sharp decrease in the abundance of S. galinae and T. planipennisi. We observed low densities of emerald ash borer larvae in our study sites between the fall 2021 and spring 2022, suggesting that low EAB densities in our study sites may have at least partly contributed to the recent reduction of parasitoid abundance. For fiscal year 2022, we also determined the dispersal distance and parasitism level of the egg parasitoid (O. agrili) shortly after field release. Results from this study showed that that the tiny egg parasitoids dispersed at least 45 m in 120 hours after field releases and levels of egg parasitism did not vary among EAB host plant species (# 390860). Through laboratory experiments, we also determined the optimal low temperature ranges for terminating the diapause of emerald ash borer larvae for effective parasitoid rearing. Preliminary data (from 3 replicates) showed that the effective range of low temperatures for termination of emerald ash borer larval diapause is from 45oF to 60oF and temperatures beyond this range has no effect on the termination emerald ash borer larval diapause. More replicates will be conducted in the next fiscal year. In addition, we have completed experiments to optimize the temperature and relative humidity for long-term cold storage of emerald ash borer eggs and its egg parasitoid (Oobius agrili) during diapause. Results showed that both low temperature (35 – 55oF) and high relative humidity (65 – 100%) are optimal conditions for long-term storage of host eggs and diapausing egg parasitoid larvae. Data on these laboratory studies will be written up for publication in the following fiscal years. SFL RESEARCH: With the assistance of cooperators at APHIS and the University of Delaware, we participated in ongoing collections of SLF eggs laid by the 2021 fall generation of SLF adults to monitor for presence of native egg parasitoids and to provide host material for behavioral studies. From some of the egg masses collected in our region (mostly northern Delaware), parasitoid wasps emerged, identified as an Anastatus species, the first records of parasitoids from SLF eggs in Delaware. Identification is underway to see if they are a native species or are adventive from elsewhere. We continued behavioral assays in quarantine of the response by the Asian egg parasitoid Anastatus orientalis to 5 species of non-target planthoppers, Pselliopus barberi, Oncometopia orbona, Flatormenis proxima, Acanalonia conica, and Poblicia fuliginosa (these studies are ongoing). Through a cooperative agreement with the Chinese Academy of Forestry, native range studies of the natural host range in non-target species in China were continued, although COVID restrictions have restricted the field work component of research in China (8010-22000-033-023S). Foreign travel by ARS was not possible, but shipments of a small number of dryinid nymphal parasitoid were sent by Chinese cooperators to APHIS cooperators attempting to establish a lab colony in the U.S. With incoming FY22 Farm Bill funds, we are also expanding research with South Korean collaborators for surveys of SLF natural enemies that may be present in the invaded South Korean range, where populations of SLF that had been very high are reported to have diminished in the past several years since natural enemies were discovered there. Incoming funds were received through project 8010-22000-033-015R (NIFA/SCRI, Biology, Management and Reducing the Impact of the Spotted Lanternfly on Specialty Crops in the Eastern USA), and Farm Bill award 8010-22000-033-071I, Biological Control of Spotted Lanternfly – FY22) that helped with the lanternfly research discussed above. QUARANTINE SERVICE: We provided quarantine services for three in-house projects at BIIRU as well as several ARS cooperators. These activities included receiving over 60 permitted consignments of three targeted pests and five species of natural enemies, consisting of incoming shipments of 3713 Agrilus planipennis adults, 1200 Spathius agrili, 2100 Tetrastichus planipennisi, 1600 Oobius agrili), and 500 Ganaspis brasiliensis. In addition, we had two outgoing shipments of ~150,000 mummies of Aphelinus hordei and Diuraphis noxia, and six outgoing shipments of 5600 Spathius galinae, one shipment of 885 Ontsira mellipes, two shipments of 200 Anoplophora glabripennis eggs to support cooperator’s research programs at several universities.We shipped several hundred brown marmorated stink bug eggs and other native stink bug adults and eggs (such as Euschistus tristigmus, Podisus maculiventris, and Murgantia histrionica) to the USDA APHIS Otis Laboratory, multiple universities, and educational institutions. We shipped 99 Trissolcus japonicus parasitoids to research collaborators at Plant & Food Research, New Zealand. In addition, we produced and shipped 2000 Ganaspis brasiliensis to 9 universities across the nation and two state departments of agriculture (New Jersey and North Carolina) for mass rearing and releases.

Accomplishments

Review Publications
Quinn, N.F., Gould, J.S., Rutledge, C.E., Fassler, A., Elkinton, J.S., Duan, J.J. 2021. Spread and phenology of Spathius galinae Belokobylskij & Strazenac (Hymenoptera: Braconidae) and Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae). Biological Control. 165:1-7. https://doi.org/10.1016/j.biocontrol.2021.104794.
Chen, Y., Iqbal, A., Lv, R., Wang, X., Desneux, N., Zang, L. 2022. Chinese oak silkworm Antherae pernyi egg, a suitable factitious host for rearing eupelmid egg parasitoids. Pest Management Science. https://doi.org/10.1002/ps.6796.
Wang, X., Ramualde, N., Desurmont, G., Smith, L., Gundersen, D.E., Grodowitz, M.J. 2021. Reproductive traits of the egg parasitoid Aprostocetus fukutai a promising biological control agent for invasive citrus longhorned beetle Anoplophora chinensis. Biocontrol. https://doi.org/10.1007/s10526-021-10118-2.
Duan, J.J., Van Driesche, R.G., Schmude, J.M., Crandall, R., Rutlege, C., Quinn, N., Slager, B.H., Gould, J.R., Elkinton, J. 2021. Significant suppression of an invasive forest pest by Spathius galinae, an introduced larval parasitoid: potential for North American ash recovery. Journal of Pest Science. 2021: 1-9. https://doi.org/10.1007/s10340-021-01441-9.
Stokes, A.A., Rafael, D.B., Duan, J.J., Grunder, D.S. 2021. Rapid spread of an introduced parasitoid for biological control of Emerald Ash Borer (Coleoptera: Buprestidae) in Maryland. Journal of Economic Entomology. https://doi.org/10.1093/jee/toab248.
Wang, X., Keena, M.A. 2021. Hybridization potential of two invasive Asian longhorn beetles. Insects. 12(12):1139. https://doi.org/10.3390/insects12121139.
Daane, K.M., Da Silva, P.G., Stahl, J.M., Scaccini, D., Wang, X. 2022. Comparative life history parameters of three stink bug pest species. Environmental Entomology. https://doi.org/10.1093/ee/nvac012.
Wei, X., Chen, Y., Wang, X., Rui-E, L., Zang, L. 2022. Demography and fitness of Anastatus japonicus reared from Antheraea pernyi as a biological control agent of Caligula japonica. Insects. https://doi.org/10.3390/insects13040349.
Rutledge, C.E., Van Driesche, R.G., Duan, J.J. 2021. Comparative efficacy of three techniques for monitoring the establishment and spread of larval parasitoids recently introduced for biological control of Emerald Ash Borer, Agrilus planipennis (Coleoptera: Buprestidae). Journal of Economic Entomology. 161:1-8. https://doi.org/10.1016/j.biocontrol.2021.104704.
Ragozzino, M., Duan, J.J., Salom, S. 2021. Interspecific competition between idiobiont larval parasitoids of emerald ash borer. Journal of Insect Behavior. https://doi.org/10.1007/s10905-021-09781-1.
Dang, Y., Wei, K., Wang, X., Duan, J.J., Jennings, D., Poland, T.M. 2021. Introduced plants induce outbreaks of a native pest and facilitate invasion in the plants' native range: Evidence from the emerald ash borer. Journal of Ecology. 2021: 1–12. https://doi.org/10.1111/1365-2745.13822.
Rossi-Stacconi, M., Wang, X., Stout, A.R., Fellin, L., Daane, K.M., Biondi, A., Stahl, J., Buffington, M.L., Anfora, G., Hoelmer, K.A. 2022. Methods for rearing the parasitoid Ganaspis brasiliensis, a promising biological control agent for invasive Drosophila suzukii. Journal of Visualized Experiments. https://doi.org/10.3791/63898.
Wang, X., Daane, K.M., Pickett, C.H., Hoelmer, K.A. 2022. Biological control of olive fruit fly in California. Contributions of Classical Biocontrol to the U.S. Food Security, Forestry, and Biodiversity, 1985-2022. 115-126.
Wang, X., Daane, K.M., Hoelmer, K.A., Lee, J.C. 2021. Biological control of spotted-wing drosophila - an update on promising agents. In: Garcia, F.R.M., editor. Drosophila suzukii Management. Cham, Switzerland: Springer. p. 143-167. https://doi.org/10.1007/978-3-030-62692-1_8.