1a. Objectives (from AD-416):
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.
1b. Approach (from AD-416):
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.
3. Progress Report:
Work under this project in FY 2018 resulted in significant progress in monitoring the landscape distribution and physiological condition of cotton insect pest populations, describing the presence and abundance of pest species relative to host crops, 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 satellite images; 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, and to distinguish boll weevils from other closely related weevil species captured in traps. These sequencing methods were also used to determine the level of intermixing among cotton fleahopper populations in weed hosts and cotton to help establish refuge requirements, as mandated by the EPA, for a new commercial plant bug Bt toxin. As part of Cooperative Research and Development (CRADA) research, two new pheromone formulations for the southern green stink bug were developed; preliminary field evaluations indicate one of the formulations is attractive to southern green stink bugs as well as other economically important stink bug species. In work addressing Objective 2, research demonstrated that southern green stink bug adults infected with cotton pathogens were capable of transmitting pathogens to as many as five bolls upon consecutive feeding; efforts are underway to determine how long stink bugs can retain and transmit these pathogens. In work addressing Objective 3, neuropeptide research demonstrated the ‘natalisin’ hormones regulated the frequency of mating in both males and females of the oriental fruit fly, a major agricultural pest. Additionally, oral administration of a biostable, non-peptide mimic in the ‘myosuppressin’ class was shown to inhibit contractions of the gut in spotted wing drosophila flies, thereby resulting in a 60% reduction of food passage through the gut and a 5-fold reduction in their lifespan. The neuropeptide work brings us closer to the development of practical neuropeptide-like substances that will be effective in controlling fruit pests in an environmentally friendly fashion.
1. Diapause and overwinter survival of the boll weevil. Understanding overwintering strategies of the boll weevil is important to completion of eradication efforts in the United States and expansion of eradication into the subtropics and tropics. Recent reports have characterized the winter-dormancy of the boll weevil as a quiescence, whereupon overwintered weevils immediately begin reproduction upon encountering fruiting cotton. Further reports have concluded the dormancy is absent in the subtropics; instead, that the weevil relies on non-cotton hosts for winter survival. ARS scientists at College Station, Texas, and Maricopa, Arizona, unambiguously demonstrated that the boll weevil dormancy is a diapause that is induced by impending maturity of the cotton crop. The diapause is relatively insensitive to temperatures typical of fall and early-winter months, and provides the weevil the capacity to survive the subtropical or tropical non-cotton season in the absence of cotton or other alternative food sources. These findings warn against the practice of extending spray intervals during the cooler fall months, and emphasize the importance to eradication and management programs of reducing populations of diapausing weevils before they abandon maturing cotton fields.
2. Morphology of the southern green stink bug feeding apparatus. Stink bugs are known to transmit plant pathogens, but it was unknown whether the size of the food canal affected ingestion and transmission of select pathogens. ARS scientists at College Station, Texas, determined the dimensions of the food canal and concluded that food canal shape and size would not impede ingestion of identified pathogens. The food canal shape was shown to be ellipsoid in cross-section. The size and shape was shown to vary along the length of the food canal, producing a ‘funnel effect’ and revealing new details about the southern green stink bug’s stylet bundle morphology. These findings expand and improve our knowledge base on stink bug mouthpart morphology, and can be incorporated in future studies addressing pathogen transmission.
3. Neuropeptide hormones that regulate water balance identified in the boll weevil. New and environmentally sensitive control strategies for the boll weevil are needed to assure ongoing effective management during eradication efforts, particularly given weevil resistance to some insecticides. ARS scientists at College Station, Texas, in collaboration with scientists at the University of Cologne, identified neuropeptides of several classes from the central nervous system of the boll weevil, including several associated with the regulation of water balance, a critical life process. The work also mapped neuropeptide storage and release sites and characterized the structures of seven distinct peptide hormones in the nervous system of these insect pests. This information will aid in determining the functional roles of these different neuropeptides in boll weevils and other related insect pests, and may lead to development of practical neuropeptide-like substances that can effectively and specifically control the boll weevil in an environmentally friendly manner.
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