Location: Insect Control and Cotton Disease Research
2020 Annual Report
Objectives
Objective 1: Develop novel detection technologies for the stink bug complex, Lepidoptera, boll weevil, and their associated host plants. (NP304, Component 3, Problem Statement 3A1 and Problem Statement 3B1).
Subobjective 1A: Enhance airborne remote sensing techniques to detect host plants.
Subobjective 1B: Improve attraction and increase duration of attractiveness of insect pheromone lures.
Subobjective 1C: Improve detection of pest insect populations in response to climate change.
Objective 2: Develop knowledge of insect-pathogen interactions and critical life functions of piercing-sucking insects to regulate and disrupt these processes. (NP304,
Component 3, Problem Statement 3A2 and Problem Statement 3B2).
Subobjective 2A: Identify hemipterans that act as pathogen reservoirs and assess potential for transmission of pathogens.
Subobjective 2B: Determine the propensity for individual infected insects to inoculate multiple bolls.
Subobjective 2C: Ascertain the retention time of pathogenic organisms within the digestive tract of hemipterans.
Objective 3: Develop pest management strategies and delivery systems, such as neuropeptide mimic-based systems, that disrupt critical life processes of insects including stink bugs, Lepidoptera, and boll weevils. (NP304, Component 3, Problem Statement 3A2 and Problem Statement 3B2).
Subobjective 3A: Identify native NP and determine their role in regulating critical life processes in stink bugs, Lepidoptera, Lygus, and boll weevils.
Subobjective 3B: Develop biostable, bioavailable mimics of regulatory NP that disrupt critical life processes of stink bugs, boll weevils, bollworms, and budworms.
Subobjective 3C: Exploit secondary metabolites of cotton plants to reduce insect pest abundance and feeding damage.
Approach
Ecologically based management of field crop pests is critical for sustaining agricultural productivity/health and for reducing costs and minimizing undesirable environmental consequences associated with reliance on chemical pesticides. This project focuses on development of pest trapping/monitoring systems to detect host plant distributions, pest abundance, pest dispersal, pest transmission of plant pathogens, and exploitation of host plant defense mechanisms and neuropeptide mimics that disrupt critical life processes of insect pests. Project objectives will be accomplished through three main research areas that lead to development of: 1) technologies that detect pests and pest habitats, and models that simulate response of pest migration to climate change; 2) methods to understand the biology and ecology of plant pathogen vectoring by stink bugs and other piercing-sucking insect pests; and 3) novel pest management technologies and strategies such as neuropeptide (NP) mimics and exploitation of host plant defense traits. Results of project research are expected to provide producers and crop consultants with the appropriate scientific knowledge and technologies to make effective pest management decisions with minimal environmental impact. This project combines entomological, biochemical, and meteorological expertise to create a research program that defines how pests utilize host plants, disperse, and infest and infect target crops, and how pest activity can be altered by the use of neuropeptide mimics and natural plant defense traits to achieve environmentally safe crop protection.
Progress Report
Work under the life of this project, which expired in fiscal year 2020, resulted in significant progress on using remote sensing technologies to detect cotton fields and regrowth, developing and evaluating new or improved pheromone formulations for the boll weevil and stink bug, modeling migration routes of key agricultural insect pests, understanding the role of stink bugs and plant bugs as vectors of cotton pathogens, and developing novel pest management technologies based on neuropeptide hormone mimics and exploitation of cotton defensive compounds. Much of this work will be expanded upon in the new 5-year replacement project, “Novel Approaches for Management of Row Crop Pests and Continued Boll Weevil Eradication”, which is currently under review and expected to be implemented by September 2020. In work addressing Objective 1, analytical methods were developed to identify cotton fields within a broad and diverse cropping landscape by analysis of multispectral images obtained by satellite and unmanned aircraft; transfer of associated technology to the Texas Boll Weevil Eradication Foundation was accomplished. Objective 1 research also used advanced genetic sequencing techniques to identify single nucleotide polymorphisms (genetic markers) to infer the geographical association of boll weevils in the Americas. This line of work was expanded to identify additional markers which will be used in work under the new project to distinguish boll weevils from other weevil species commonly captured in traps. Similar sequencing methods and genomic approaches were also used to investigate the spatial scale of cotton fleahopper movement from weed hosts into cotton fields, and to determine the level of intermixing among fleahopper populations in weed hosts and cotton. This work was used to establish refuge requirements, as mandated by the Environmental Protection Agency, for the new plant bug Bacillus thuringiensis toxin developed by industry. As part of industry partner research, new prototype boll weevil pheromone lures were developed and aged under field conditions. The new prototypes release pheromone more uniformly than the current lures used in eradication programs, but additional refinements to the formulation and subsequent trapping studies are needed to evaluate the attraction of weevils to the new lures. In other work addressing Objective 1, the migration routes of several key insect pests, including the sugarcane aphid and fall armyworm, were modeled to allow better prediction of their respective temporal and spatial movement patterns across the agricultural landscape as well as throughout the continental U.S. Work addressing Objective 2 provided a clearer understanding of the interaction between stink bugs and cotton pathogens, and the mechanisms by which stink bugs obtain and transmit pathogens that cause disease in cotton. Work under this objective established that stink bugs were primary vectors of several boll rot pathogens, and showed that both adults and nymphs could retain pathogens for prolonged periods and infect multiple cotton bolls in succession. Work under this objective also revealed that the tarnished plant bug can obtain, harbor, and transmit certain pathogens that cause disease in cotton. Work under Objective 3 identified several classes of insect neuropeptide hormones which led to the development of neuropeptide mimics that affect diapause, reproduction, diuresis, and other critical life processes of several agricultural pests including aphids, oriental fruit flies, and corn earworms. More recently, over 100 neuropeptide hormones were identified as potential targets in the development of environmentally safe pest control agents of the Asian citrus psyllid, an important pest of citrus. In other work addressing Objective 3, laboratory feeding assays confirmed the importance of gossypol, hemigossypolone, and heliocides as feeding deterrents for bollworm larvae. Work under this objective also led to the development of a tri-species cotton hybrid that produces three unique caryophyllene derivatives; caryophyllenes are a type of chemical (sesquiterpene) produced by a number of higher plants and are commonly used as an ingredient in insect repellents. Based on preliminary greenhouse and small-scale field studies, plants expressing the caryophyllene alcohol derivative had fewer insect pests and/or sustained less feeding damage compared with control plants. Efforts are underway to increase seed production of plants expressing these caryophyllene derivatives for larger-scale field trials, and the release of germplasm lines expressing one or more of these derivatives is expected in the near future.
Accomplishments
1. Refuge requirements for a new transgenic cotton line. A new Bacillus thuringiensis (Bt) toxin was specifically developed for the tarnished plant bug, but the toxin also has activity against several other insect pests including the cotton fleahopper. Before transgenic cotton expressing this new toxin can be released commercially, a management strategy to delay or prevent resistance to the Bt toxin must be approved by the Environmental Protection Agency for all targeted insects. ARS researchers at College Station, Texas, in collaboration with researchers at Texas A&M University, compared the genomic structure of cotton fleahopper populations in cotton and nearby patches of wild weed hosts throughout the year. Based on the abundant numbers of cotton fleahoppers found in nearby weed hosts, and the high level of intermixing among cotton fleahopper populations in weed hosts and cotton fields throughout the growing season, the work indicated that planting of non-Bt cotton plants (refuge) in the proximity of the Bt cotton is not necessary; instead, nearby wild weed hosts could serve as a natural refuge for the new Bt cotton intended for plant bugs. This accomplishment is important in assuring proper regulation of the technology while avoiding needless restrictions.
2. Pathogen transmission potential of stink bugs. Stink bugs can transmit plant pathogens that affect cotton yield quality and quantity, yet the ability and frequency of individual stink bugs to infect multiple cotton bolls in succession is not known. ARS researchers at College Station, Texas, determined that an individual southern green stink bug could infect at least five bolls in succession. Current treatment thresholds for this insect pest are based on the numbers of stink bugs per unit area without any consideration of whether stink bugs are infected with pathogens. This research is important because it shows that current action thresholds based solely on stink bug numbers should be reconsidered given the potential for individual southern green stink bugs to infect multiple bolls.
3. Hormone mimics as safe, selective, and effective aphicidal agents. Aphids are significant agricultural pests in temperate regions, causing yellowing, mottled leaves, stunted growth, curled leaves, low yields, and death through disease transmission. New approaches are needed for effective aphid management and control. ARS researchers at College Station, Texas, in collaboration with researchers from Belgium and the United Kingdom, developed stable mimics of two neuropeptide hormones that cause large-scale mortality in the peach potato aphid when applied together in a topical manner that simulates a spray application scenario in the field. Notably, this treatment was shown to be selective, having no effects on beneficial insects such as natural enemies and pollinators. This research is significant because it demonstrates the potential of using neuropeptide hormone mimics as environmentally safe pest aphid management agents, which will minimize or obviate the use of less selective and less environmentally sensitive conventional insecticides.
Review Publications
Westbrook, J., Fleischer, S., Jairam, S., Meagher Jr, R.L., Nagoshi, R.N. 2019. Multigenerational migration of fall armyworm, a pest insect. Ecosphere. 10(11). https://doi.org/10.1002/ecs2.2919.
Esquivel, J.F., Medrano, E.G. 2019. Transmission of Eremothecium coryli (syn. Nematospora coryli) to consecutive cotton bolls by individual stink bugs. Southwestern Entomologist. 44(4):853-860. https://doi.org/10.3958/059.044.0414.
Esquivel, J.F., Glover, J.P., Brewer, M.J., Helms, A.M., Ree, W.O., Shirley, X.A., Bell, A.A. 2020. Expansion of geographical range and plant associations of Leptoglossus clypealis: A potential invasive pest of sorghum along the Texas Gulf Coast. Southwestern Entomologist. 45(1):1-16.
Wu, Q., Hu, G., Westbrook, J.K., Sword, G.A., Zhai, B. 2018. An advanced numerical trajectory model tracks a corn earworm moth migration event in Texas, USA. Insects. 9:115. https://doi.org/10.3390/insects9030115.
Fleites, L.A., Johnson, R., Kruse, A.R., Nachman, R.J., Hall, D.G., Maccoss, M., Heck, M.L. 2020. Peptidomics approaches for the identification of bioactive molecules from Diaphorina citri . Journal of Proteome Research. 19/4; 1392-1408. https://doi.org/10.1021/acs.jproteome.9b00509.
Avila-Quezada, G., Esquivel, J.F., Silva-Rojas, H.V., Leyva-Mir, S.G., Garcia-Avila, C.I., Quezada-Salinas, A., Noriega-Orozco, L., Rivas-Valencia, P., Ojeda-Barrios, D., Melgoza-Castillo, A. 2018. Emerging plant diseases under a changing climate scenario: Threats to our global food supply. Emirates Journal of Food and Agriculture. 30(6):443-350.
Park, J., Thomasson, J., Lee, K., Suh, C.P., Perez, J.L., Herrman, T.J. 2020. VOCs determination by adsorbent-Raman system in food and botanicals. Talanta. 12:1595-1605. https://doi.org/10.1039/d0ay00180e.
Raszick, T.J., Suh, C.P., Dickens, C.M., Sword, G.A. 2019. Genome-wide markers reveal temporal instability of local population genetic structure in the cotton fleahopper, Pseudatomoscellis seriatus (Hemiptera: Miridae). Pest Management Science. 76:324-332. https://doi.org/10.1002/ps.5518.
Suh, C.P., Spurgeon, D.W., Reardon, B.J. 2020. Reproductive and survival responses of overwintered boll weevils (Coleoptera: Curculionidae) to diet. Journal of Entomological Science. 55(1):58-68. https://doi.org/10.18474/0749-8004-55.1.58.
