Research Project: Classical Biological Control of Insect Pests of Crops, Emphasizing Brown Marmorated Stink Bug, Spotted Wing Drosophila and Tarnished Plant Bug

Location: Beneficial Insects Introduction Research Unit

2020 Annual Report

Objectives
1: Discover, characterize, identify, evaluate the efficacy, and determine the ecological safety of exotic predators and parasitoids as classical biological control agents of invasive insect pests, including tarnished plant bug, brown marmorated stink bug, and spotted wing drosophila, and may include other new invasive species, such as kudzu bug. Sub-objective 1A: Discovery Sub-objective 1B: Characterization and identification Sub-objective 1C: Evaluation and risk assessment 2: Develop an improved understanding of factors and processes that influence the successful establishment of introduced biological control agents, such as climate adaptation, release methodologies, genetic variation in source and founder populations, using natural enemies of current target pests as model systems. Sub-objective 2A: Conduct retrospective analyses of current/past biological control programs (where appropriate). Sub-objective 2B: Conduct laboratory and field studies of selected biological traits and ecological requirements relevant to the establishment and efficacy of the target biological control agents. 3: Prepare (with collaborators, when appropriate and necessary) petitions to regulatory agencies for field release of candidate agents, conduct field releases for establishment of new agents, and monitor and evaluate the impact of these natural enemies on target pest populations and on non-target species in the field. Sub-objective 3A: Develop and submit a petition for release that describes the importance of the target pest and the efficacy and safety of the candidate biocontrol agent; and participate in the regulatory decision process as needed. Sub-objective 3B: Conduct releases and post-release monitoring (with cooperators when necessary) of permitted natural enemies.

Approach
Classical (importation) biological control is a pest management technology that is environmentally safe and sustainable. This project focuses on discovery, evaluation, and establishment of classical biological control agents of selected agricultural pests in the U.S. Previous research continued into this project addresses as targets tarnished plant bugs, brown marmorated stink bug; and spotted wing drosophila. New targets may be added at any time according to national need. To address objective (1) we will conduct foreign exploration in Asia and other regions as needed to discover, identify and evaluate the biology, ecology, and efficacy of exotic predators and parasitoids as classical biological control agents of the targeted pests. Agents discovered in exploration will be returned to our laboratory and identified using the best available morphological characters in conjunction with molecular sequence data, and evaluated in our quarantine facility for efficacy by measuring attack rates, reproductive output and development rates, and for host specificity by testing both close relatives to target hosts and progressively more distantly related species under choice and no-choice conditions. Objective (2) will address the role of environmental factors such as climate and photoperiod or inherent genetic variability in determining establishment success. Using a parasitoid of tarnished plant bug that established in some regions of the US but not others as the model subject, we will characterize the genetic variability of populations established in the US and their relation to genetic source populations in Europe. Using parasitoids of any or all target pests, we will test the influence of differing environmental factors such as temperature, soil moisture and photoperiod regimes on parasitoid survival in environmental growth chambers and comparative field exposures. To address objective (3) we will prepare petitions for field release of qualified candidate agents of all target pests determined to be both effective and safe, based on satisfactory results of evaluation studies. These will be submitted to technical advisory panels and APHIS, in collaboration with relevant project partners as necessary. Supplemental research will be conducted to provide additional information if requested by APHIS. Once permits are received we will participate with cooperators as needed in conducting releases and post-release monitoring of the natural enemies. Where possible the releases will be designed to compare different geographic populations or genetic accessions of the agent for differences in climate adaptation, efficacy or other behavioral characteristics.

Progress Report
Populations of the brown marmorated stink bug (H. HALYS) have been significant pests in soybeans, vegetables, nut and various tree fruits in the eastern and northwestern U.S. for the past decade, and their impact is still increasing in other U.S. regions. ARS Newark continued to provide technical support to cooperators across the U.S. for sentinel surveys to monitor parasitism of H. HALYS by resident native stinkbug parasitoids in different crop systems, including survey protocols, workshops (annual workshops have been given in each year of this project for U.S. cooperators and for foreign cooperators in April 2019 in Montpellier, France in association with ARS European Biological Control Lab (EBCL and identification of specimens (Objectives 1B & 3B; annual Farm Bill awards). Similar training was provided for new cooperators who have begun regional research on spotted lanternfly, LYCORMA DELICATULA, a recently invasive pest of grapes, hops, and potentially of other forest trees and tree fruit. Foreign exploration was conducted during the first four project years in China for natural enemies of the lantern fly but could not be conducted as planned in 2020 due to COVID. Foreign collections focused on natural enemies of lanternfly eggs and nymphs and an egg parasitoid, ANASTATUS ORIENTALIS, and a nymphal parasitoid, DRYINUS SINICUS, have been identified as candidate agents. Initially thought to be a different species, we worked with dryinid taxonomists in the U.S. and Italy to obtain a definitive confirmation of their identity. Adult wasps attack young nymphs of lanternfly in early summer. Difficult to spot in the field as adults, wasps were recovered from sticky bands wrapped around trees to trap lanternfly nymphs and were collected for taxonomic research and identification. Parasitized lanternfly nymphs were found in substantial numbers at several of the surveyed sites, and several hundred live parasitized second and third instar nymphs were successfully hand-carried back to the U.S. to the Beneficial Insects Introduction Research Unit (BIIRU) quarantine facility for further studies in 2018 and 2019 but maintaining this species in culture is proving difficult and further research is required. At BIIRU larval dryinids emerged from many of these parasitized nymphs collected during the previous summer of 2018 and were placed into winter temperature regimes and held for overwintering studies still in progress (Objective 2B). Lanternfly research contributed to Obj. 1A & 1B. Host range studies of the Asian egg parasitoid ANASTATUS ORIENTALIS which attacks lanternfly eggs were initiated through cooperative agreement with Univ. Delaware and Animal and Plant Health Inspection Service Plant Protection and Quarantine (PHIS PPQ) cooperators which funds a University of Delaware graduate student to collect and rear a range of nontarget planthoppers for host range suitability and taxonomic studies of native U.S. ANASTATUS egg parasitoids (Obj. 1C). Behavioral experiments showed that the egg parasitoid A. ORIENTALIS recognizes kairomones deposited by adult lanternflies on trees, causing it to alter its behavior by using these cues to intensify searches for lanternfly eggs to attack (publication log362241). Preliminary experiments showed that kairomones from a non-target planthopper do not elicit the same degree of searching activity, evidence of a degree of behavioral host specificity. During the first four project years additional field collections of TRISSOLCUS parasitoids of Asian stink bugs and a range of larval and pupal parasitoids of spotted wing drosophila, DROSOPHIA SUZUKII, were obtained for taxonomic and genetic studies (Objective 1B) in collaboration with ARS EBCL and Systematic Entomology Lab (SEL) and a Florida state cooperator (publication logs 367017, 367652) and for host range and biological studies (Objective 2A) in support of host range evaluations by cooperators. Subsequent to a white paper for Office of National Programs on the subject, exploration in China, Taiwan and South Korea was initiated in 2019 with APHIS and foreign cooperators for natural enemies of roseau cane scale, an invasive pest that has established along the U.S. Gulf Coast and which is killing large areas of roseau cane (PHRAGMITES reed), dense stands of which are important for reducing coastal and shipping channel erosion. Exploration could not be pursued in 2020 due to COVID but Farm Bill-funded Non-Assistance Cooperative Agreements (NACA) are in place for native range research by cooperators. Laboratory research on the diapause requirements and climatic suitability for different regions of the U.S. of GANASPIS BRASILIENSIS, a larval-pupal parasitoid of the spotted wing drosophila DROSOPHILA SUZUKII, was continued in 2019 (Objective 2B). Research in 2020 continued on improving the artificial diet and rearing methods in order to support mass production of the parasitoid for eventual field release (Obj. 3C). Research was conducted in the field and the laboratory to assess the potential impact of Asian TRISSOLCUS JAPONICUS on non-target species in the U.S. Research on the behavioral response of the parasitoid TRISSOLCUS JAPONICUS to its host and to non-target kairomones (chemical footprints) was started with laboratory observations. The response varied significantly, with residence times on H. HALYS footprints being significantly longer than on spined soldier bug (an important beneficial non-target species) footprints; this response was not significantly different for exposure to either female and to male host stinkbugs. T. JAPONICUS remained the least amount of time on leaves that were uncontaminated with host chemical footprints. These trends were also reflected in walking velocity of parasitoids, with parasitoids walking fastest on untreated clean leaves and slowest on leaves contaminated by H. HALYS l footprints. The wasp responded in similar manner to immature nymphal stages of H. HALYS, but not to immature spined soldier bugs. The results showed that although T. JAPONICUS can detect the chemical footprints of the adult non-target spined soldier bug, they have a much stronger behavioural response to H. HALYS, and thus are likely to spend more time in searching for stink bug eggs on plants contaminated by H. HALYS (publication logs 355551, 368478). Extracts of the kairomones were isolated and identified in collaboration with ARS-Invasive Insect Biocontrol and Behavior Laboratory (IIBBL) in Beltsville. Two compounds, E-2-decenal and tridecane, appear to be the major components of the BMSB kairomone that elicit a TRISSOLCUS response. During 2019 and 2020 field seasons, this response was examined in field trials to determine if host kairomones would increase the chances that parasitoids will discover host stink bug eggs under actual field conditions (study is still underway). The studies indicate that behavioral and ecological responses will likely moderate and reduce the potential non-target impact of this Asian parasitoid (Objective 1C). A similar approach was used to assess the behavioral response of the lanternfly egg parasitoid ANASTATUS ORIENTALIS to lanternfly eggs (described above). Field collections in Asia were continued of parasitoids of other stink bug species to document the actual host stink bug range of TRISSOLCUS in the native range. The data is important for a U.S. release petition nearing completion. A similar petition was submitted in FY19 for field releases in Canada, for which we contributed our research data (obj. 3A); their petition was not granted however, pending availability of additional information from field surveys, which we will include in the U.S. petition. Surveys were continued to monitor the overwinter survival, establishment and spread of TRISSOLCUS JAPONICUS, the Asian parasitoid of H. HALYS. Discovered in the U.S. in 2014, it was newly found in Michigan and California during 2018 and in Utah in 2019, bringing the total known adventive distribution to thirteen U.S. states, the D.C., and four adjacent Canadian provinces. It has also been found adventively in Europe (publication logs 373618, 359071, 358426). This research addresses Objective 1. In Delaware, the adventive TRISSOLCUS was redistributed within the state to accelerate its establishment and expand its range of occurrence (Objective 3B). Additional host range research was conducted with cooperators in Italy and New Zealand to extend ARS research in support of stink bug biological control programs in those countries (publication log 347539).

Accomplishments

Review Publications
Charles, J.G., Avila, G.A., Hoelmer, K.A., Hunt, S., Gardner-Gee, R., MacDonald, F., Davis, V. Experimental assessment of the biosafety of Trissolcus japonicus in New Zealand, prior to the anticipated arrival of the invasive pest Halyomorpha halys. BioControl 64, 367–379 (2019). https://doi.org/10.1007/s10526-019-09949-x
Malek, R.N., Kaser, J.M., Broadley, H.J., Gould, J., Ciolli, M., Anfora, G., Hoelmer, K.A. 2019. Footprints and ootheca of Lycorma delicatula influence host-searching and -acceptance of the egg-parasitoid Anastatus orientalis. Environmental Entomology. 48(6): 1270-1276. https://doi.org/10.1093/ee/nvz110.
Acebes-Doria, A.L., Agnello, A.M., Alston, D.G., Andrews, H., Beers, E.H., Bergh, J., Bessin, R., Blaauw, B.R., Buntin, G., Burkness, E.C., Chen, S., Cottrell, T.E., Daane, K.M., Fann, L.E., Fleischer, S.J., Guedot, C., Gut, L.J., Hamilton, G.C., Hilton, R., Hoelmer, K.A., Hutchison, W.D., Jentsch, P., Krawczyk, G., Kuhar, T.P., Lee, J.C., Milnes, J.M., Nielsen, A.L., Patel, D.K., Short, B.D., Sial, A.A., Spears, L.R., Tatman, K.M., Toews, M.D., Walgenbach, J.D., Welty, C., Wiman, N.G., Van Zoeren, J., Leskey, T.C. 2019. Season-long monitoring of the brown marmorated stink bug (Hemiptera: Pentatomidae) throughout the United States using commercially available traps and lures. Journal of Economic Entomology. 113(1):159-171. https://doi.org/10.1093/jee/toz240.
Bon, M., Talamas, E., Hoelmer, K.A., Buffington, M.L. 2019. Molecular phylogeny of Trissolcus wasps (Hymenoptera: Scelionidae), natural enemies of stink bugs. Journal of Hymenoptera Research. 73:201-217.
Sabbatini Peverieri, G., Mitroiu, M., Bon, M., Balusu, R., Benvenuto, L., Bernardinelli, I., Fadamiro, H., Falagiarda, M., Fusu, L., Grove, E., Haye, T., Hoelmer, K.A., Lemke, E., Malossini, G., Marianelli, L., Moore, M.R., Pozzebon, A., Roversi, P., Scaccini, D., Shrewsbury, P., Tillman, P.G., Tirello, P., Waterworth, R., Talamas, E. 2019. Surveys of stink bug egg parasitism in Asia, Europe and North America, morphological taxonomy, and molecular analysis reveal the Holarctic distribution of Acroclisoides sinicus (Huang & Liao) (Hymenoptera: Pteromalidae). Journal of Hymenoptera Research. 74: 123-151. https://doi.org/10.3897/jhr.74.46701.
Boyle, S.M., Weber, D.C., Hough-Goldstein, J., Hoelmer, K.A. 2019. Host kairomones influence searching behavior of Trissolcus japonicus (Hymenoptera: Scelionidae), a parasitoid of Halyomorpha halys (Heteroptera: Pentatomidae). Environmental Entomology. 49(1):15-20. https://doi.org/10.1093/ee/nvz155.
Ludwick, D.C., Morrison III, W.R., Acebes-Doria, A.L., Agnello, A.M., Bergh, J., Buffington, M.L., Hamilton, G.C., Harper, J.K., Hoelmer, K.A., Krawczyk, G., Kuhar, T.P., Pfeiffer, D.G., Nielsen, A.L., Rice, K.B., Rodriguez-Saona, C., Shearer, P.W., Shrewsbury, P.M., Talamas, E.J., Walgenbach, J.F., Wiman, N.G., Leskey, T.C. 2020. Invasion of the brown marmorated stink bug (Hemiptera: Pentatomidae) into the USA: developing a national response to an invasive species crisis through collaborative research and outreach efforts. Journal of Integrated Pest Management. 11(1):1-16. https://doi.org/10.1093/jipm/pmaa001.
Sabbatini Peverieri, G., Giovannini, L., Benvenuti, C., Madonni, L., Hoelmer, K.A., Roversi, P. 2020. Characteristics of the meconia of European egg parasitoids of Halyomorpha halys. Journal of Hymenoptera Research. 77:187-201. https://doi.org/10.3897/jhr.77.52904.
Boyle S, Weber D., Hough-Goldstein J, Hoelmer KA. Parental host species affects behavior and parasitism by the pentatomid egg parasitoid Trissolcus japonicus (Hymenoptera: Scelionidae). Biological Control 149: 104324. 2020. https://doi.org/10.1016/j.biocontrol.2020.104324