Location: Insect Control and Cotton Disease Research
2019 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 this project in FY 2019 resulted in significant progress on using remote sensing technologies to detect cotton fields, developing genomic methods and tools to distinguish boll weevil populations from different geographical regions in the Americas, developing and evaluating a new pheromone formulation for the southern green stink bug, and developing novel biologically-based pest management technologies. 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 un-manned aircraft; transfer of associated technology to the Texas Boll Weevil Eradication Foundation is underway. Advanced genetic sequencing techniques were used to identify genetic markers to infer the geographical association of boll weevils in the Americas. This line of work was recently expanded to identify additional markers which will be used to distinguish boll weevils from other weevil species commonly captured in traps. Similar sequencing methods were also used to estimate the level of intermixing among cotton fleahopper populations in weed hosts and cotton to help establish refuge requirements, as mandated by EPA, for the new plant bug Bt toxin developed by industry. As part of CRADA/MTRA research, olfacotometer and field evaluations were initiated to assess the attractiveness of a new pheromone formulation for the southern green stink bug (SGSB). Preliminary results revealed that SGSB adults, as well as those of other stink bug species, were attracted to the new pheromone formulation. Work addressing Objective 2 established that stink bugs are capable of penetrating the carpel wall of cotton bolls throughout the entire production season, regardless of cotton species, variety, or age of bolls. Work under Objective 3 developed a stabile mimic of the CAPA class of neuropeptides that is active against aphids. The stabilized neuropeptide versions (‘mimics’) are resistant to inactivation by the insect body enzymes and cause significant mortality in the peach potato, and rose aphid under unstressed conditions, and also under desiccation and cold stress. In other work addressing Objective 3, a cotton hybrid was developed that produces three unique caryophyllene derivatives that may repel or deter insect feeding; caryophyllenes are a type of chemical (sesquiterpene) produced by a number of higher plants including cotton. Greenhouse and field studies were initiated to evaluate the hybrid against a number of cotton insect pests (thrips, aphids, whiteflies, and fall armyworm).
Accomplishments
1. Overwintering strategies of the boll weevil in sub-tropical climates. Understanding overwintering strategies of the boll weevil in the sub-tropics, where fruiting cotton plants may exist year-round, is important to completion of boll weevil eradication efforts in the U.S. Although it is widely recognized that overwintered weevils feed and reproduce on fruiting cotton during the fallow season, the ecological implications of these plants on survival of overwintered weevils have not been established. ARS scientists at College Station, Texas, and Maricopa, Arizona, discovered that overwintered weevils fed fruiting plants could accumulate fat which allowed substantially greater host-free longevity compared with overwintered weevils that were not fed. Although the contributions of diapause and fallow-season reproduction to boll weevil overwintering survival are commonly recognized, findings of this study identify an additional mechanism by which overwintered boll weevils may utilize regrowth and volunteer cotton to enhance survival during the fallow season. This information reinforces the importance of eliminating cotton plants during the fallow season, and provides boll weevil eradication programs with information necessary to improve ongoing eradication efforts.
2. Stylet penetration potential in stink bugs. Stink bugs use slender needle-like mouthparts (stylets) to penetrate the developing cotton fruit (boll) and potentially introduce plant pathogens. The stylets are housed within a four-segmented beak (rostrum). Recent observations indicated some stink bug species with shorter beaks unexpectedly yielded deeper stylet penetration estimates than stink bugs with longer beaks. ARS scientists at College Station, Texas, showed that the lengths of beak segments one and two played a pivotal role in allowing deeper stylet penetration for stink bug species possessing shorter beaks. The work revealed that the stylet penetration potential of stink bugs was more dependent on the length of the first two beak segments rather than the overall length of the beak. This discovery contributes to general knowledge regarding stink bug feeding mechanics, and sheds new light on a factor that may influence disease transmission by stink bugs.
3. Molecular pathways involved in diapause termination in corn earworms. Corn earworms have developed resistance to several Bt toxins and conventional insecticides. Consequently, new approaches are needed to manage this devastating insect pest. Neuropeptides of the ‘diapause hormone’ class regulate the ability of crop pest insects to survive harsh winter conditions by entering into a protective state of hibernation known as diapause. ARS scientists at College Station, Texas, in collaboration with scientists at Ohio State University, established the precise cascade of molecular pathways that the diapause hormone and its mimics initiate to elicit termination of diapause in the corn earworm. This discovery sheds important light on how the process of diapause may be manipulated to the detriment of corn earworms, and will aid in the design of neuropeptide-like compounds capable of disrupting the survival behaviors of corn earworms and that may be effective in control of this important insect pest.
Review Publications
Xiong, C., Kaczmarek, K., Zabrocki, J., Pietrantonio, P.V., Nachman, R.J. 2019. Evaluation of Aib and PEG-polymer insect kinin analogs on mosquito and tick GPCRs identifies potent new pest management tools with potentially enhanced biostability and bioavailability. General and Comparative Endocrinology. 278:58-67. https://doi.org/10.1016/j.ygcen.2018.08.002.
Reynolds, J.A., Nachman, R.J., Denlinger, D.L. 2019. Distinct microRNA and mRNA responses elicited by ecdysone, diapause hormone and a diapause hormone analog at diapause termination in pupae of the corn earworm, Helicoverpa zea. General and Comparative Endocrinology. 278:68-78.
Pietrantonio, P.V., Xiong, C., Nachman, R.J., Shen, Y. 2018. G protein-coupled receptors in arthropod vectors: Omics and pharmacological approaches to elucidate ligand-receptor interactions and novel organismal functions. Current Opinion in Insect Science. 29:12-20. https://doi.org/10.1016/j.cois.2018.05.016.
Esquivel, J.F. 2019. Stink bug rostrum length vs. stylet penetration potential. Entomologia Experimentalis et Applicata. 167(4):323-329. https://doi.org/10.1111/eea.12782.
Spurgeon, D.W., Suh, C.P. 2019. Termination of diapause in the boll weevil (Coleoptera: Curculionidae). Journal of Economic Entomology. 112(2):633-643. https://doi.org/10.1093/jee/toy392.
Esquivel, J.F., Hinze, L.L. 2019. The cotton boll: The relationship of species and genotype with temporal development of boll wall thickness. Crop Science. 59:1200-1210. https://doi.org/10.2135/cropsci2018.08.0527.
Esquivel, J.F., Hinze, L.L. 2019. The cotton boll: Temporal susceptibility of the boll wall to stylet penetration by hemipteran pests. Crop Science. 59(3):1211-1221. https://doi.org/10.2135/cropsci2018.08.0528.
Alford, L., Marley, R., Dornan, A., Dow, J., Nachman, R.J., Davies, S. 2019. Dessication, thermal stress and associated mortality in Drosophila fruit flies induced by neuropeptide analogue treatment. Journal of Pest Science. 92(3):1123-1137. https://link.springer.com/article/10.1007/s10340-019-01100-0.
Spurgeon, D.W., Suh, C.P., Esquivel, J.F. 2018. Diapause response of the boll weevil (Coleoptera: Curculionidae) to feeding period duration and cotton square size. Journal of Insect Science. 18(5):1-5.
Spurgeon, D.W., Suh, C.P., Esquivel, J.F. 2019. Diapause response of the boll weevil (Coleoptera: Curculionidae) to selected diets. Journal of Entomological Science. 54(1):61-78. https://doi.org/10.18474/JES18-49.
Alford, L., Marley, R., Dornan, A., Pierre, J., Dow, J., Nachman, R.J., Davies, S. 2019. Assessment of neuropeptide binding sites and the impact of biostable kinin and CAP2b analogue treatment on aphid (Myzus persicae and Macrosiphum rosae) stress tolerance. Pest Management Science. 75(6):1750-1759. https://doi.org/10.1002/ps.5372.
