Location: Insect Control and Cotton Disease Research
2016 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 2016 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, individual volunteer cotton plants were identified within mixed vegetation by analysis of airborne multispectral reflectance images acquired by consumer-grade cameras. Advanced genetic sequencing techniques and other population genomic tools are being used to develop genetic markers to infer the geographical association of boll weevils, and to distinguish boll weevils from other closely related weevil species. The same genomic tools are also being 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. Pheromone components of the southern green stink bug were confirmed and various components were synthesized. Several pheromone blends were developed for testing in olfactometer and trapping studies. In work addressing Objective 2, progress was made through collection and storage of insect samples to determine microbial fauna of hemipteran insect pests. Further progress indicates pathogen-infected southern green stink bugs can consecutively inoculate several cotton bolls. In work addressing Objective 3, evaluations of insect pest abundance and feeding damage on cotton plants containing a high ratio of the natural compounds (+)-gossypol to (-)-gossypol are being continued. Additionally, laboratory feeding bioassays using RNAi cotton plants (gossypol pathway blocked) confirmed the importance of the natural compounds gossypol and hemigossypolone as feeding deterrents for bollworm larvae. However, research findings also suggest other terpene aldehydes play an important role in defending plants against bollworms. The molecular interaction of sulfakinin (SK) neuropeptides with their ‘active site’ was characterized in the red flower beetle that regulate feeding and satiety in this and other insects and represents an integral part of strategies critical for their survival. The information will aid in the development of SK mimics capable of controlling this pest of stored grain by disruption of its feeding and suppression of appetite. Biostable mimics of the ‘insect kinin’ neuropeptide class have been shown to significantly reduce blood feeding and prevent a normal developmental process in the blood gorging Chagas’ disease vector, the kissing bug. A particular subset of the ‘insectatachykinin’ (ITK) hormone family was discovered that is highly specific to the active site of the Varroa mite. This hormone subset can serve as a template for the design of effective acaricides that are specific to mites and yet safe to use in the presence of honeybees.
Accomplishments
1. Ensuring boll weevil detection with pheromone traps. Boll weevil eradication programs rely on kill strips containing the insecticide dichlorvos to rapidly kill captured weevils and arthropods, thereby reducing the incidence of weevil escape and predation of captured weevils, and simplifying servicing of traps. Although programs have historically used a 4-week replacement interval for kill strips, recent concerns have been raised regarding their duration of effectiveness. ARS researchers at College Station, Texas, quantified the weekly residual content of insecticide (dichlorvos) in kill strips aged within pheromone traps up to four weeks under a range of environmental conditions. The research revealed that the weekly amounts of insecticide emitted by kill strips declined rapidly, and amounts emitted after two weeks were likely too low to kill the trapped weevils. Based on these findings and given the high costs associated with failure of detecting incipient weevil populations, the Texas Boll Weevil Eradication Foundation and Mexico Boll Weevil Eradication Program adopted a two-week replacement interval for kill strips.
2. Effective delivery of a novel pest control compound. Insect pests have developed resistance to several conventional pesticides, and new approaches that target critical life processes are needed for pest management. Although neuropeptides (short chains of amino acids) serve as potent messengers in insects to regulate vital functions, the neuropeptides themselves hold little promise as pest control agents because they can be degraded in the target pest and fail to efficiently penetrate the outside barrier of insects. New, selective control agents may be developed by designing mimics of these neuropeptides that both resist degradation and show greater penetrability that either inhibit or over-stimulate critical neuropeptide-regulated life functions. One such life function is the dormant state known as diapause which is widely exploited by insects to circumvent winter and other adverse seasons. ARS researchers at College Station, Texas, in collaboration with scientists from the Ohio State University, developed novel versions of neuropeptides of the ‘Diapause Hormone’ class that, for the first time, penetrate the outer barrier of pupae of heliothine insects, preventing them from entering the protective state of diapause and inducing them to commit a form of ‘ecological suicide’. The work represents a major breakthrough in the development of a completely new, practical, and environmentally friendly strategy based on neuropeptide-like substances for control of pest insects via disruption of diapause.
None.
Review Publications
Zhang, Q., Nachman, R.J., Kaczmarek, K., Kierus, K., Janusz, Z., Denlinger, D.L. 2015. Development of neuropeptide analogs capable of traversing the integument: A case study using diapause hormone analogs in Helicoverpa zea. Journal of Insect Biochemistry and Molecular Biology. 67:87-93.
Westbrook, J.K., Nagoshi, R.N., Meagher Jr, R.L., Fleischer, S.J., Jairam, S. 2015. Modeling seasonal migration of fall armyworm moths. International Journal of Biometeorology. 60:255-267.
Suh, C.P., Perez, J.L., Berg, A.L., Westbrook, J.K. 2016. Quantification of dichlorvos released from kill strips used in boll weevil eradication programs. Journal of Cotton Science. 20:26-30.
Westbrook, J.K., Eyster, R.S., Yang, C., Suh, C.P. 2016. Airborne multispectral identification of individual cotton plants using consumer-grade cameras. Remote Sensing Applications: Society and Environment. 4:37-43.
Lange, A.B., Nachman, R.J., Kaczmarek, K., Zabrocki, J. 2016. Biostable insect kinin analogs reduce blood meal and disrupt ecdysis in the blood-gorging Chagas’ disease vector, Rhodnius prolixus. Peptides. 80:108-113.
Zhang, Q., Nachman, R.J., Denlinger, D.L. 2015. Diapause hormone in the Helicoverpa/Heliothis complex: A review of gene expression, peptide structure and activity, analog and antagonist development, and the receptor. Peptides. 72:196-201.
Yu, N., Zotti, M.J., Scheys, F., Braz, A.S., Penna, P.H., Nachman, R.J., Smagghe, G. 2015. Flexibility and extracellular opening determine the interaction between ligands and insect sulfakinin receptors. Scientific Reports. 5:12627.
Jiang, H., Dobesh, S., Donghun, K., Evans, J.D., Nachman, R.J., Krzysztof, K., Janusz, Z., Park, Y. 2016. Ligand selectivity in tachykinin and natalisin neuropeptidergic systems of the honey bee parasitic mite Varroa destructor. Scientific Reports. 6:19547. doi: 10.1038/srep19547.
Esquivel, J.F., Brown, V.A., Harvey, R.B., Droleskey, R.E. 2015. A black color morph of adult Nezara viridula (L.). Southwestern Entomologist. 40(3):649-652.
Stipanovic, R.D., Puckhaber, L.S., Frelichowski, J.E., Esquivel, J.F., Westbrook, J.K., O Neil, T.M., Bell, A.A., Dowd, M.K., Hake, K., Duke, S.E. 2015. Gossypolhemiquinone, a dimeric sesquiterpenoid identified in cotton (Gossypium). Phytochemistry. 122:165-171.
Medrano, E.G., Bell, A.A., Greene, J.K., Roberts, P.M., Bacheler, J.S., Marios, J.J., Wright, D.L., Esquivel, J.F., Nichols, R.L., Duke, S.E. 2015. Relationship between piercing-sucking insect control and internal lint and seed rot in Southeastern cotton (Gossypium hirsutum). Journal of Economic Entomology. 108:1540-1544.
Crippen, T.L., Sheffield, C.L., Byrd, J.A., Esquivel, J.F., Beier, R.C., Yeater, K.M. 2016. Poultry litter and the environment: Physiochemical properties of litter and soil during successive flock rotations and after remote site deposition. Science of the Total Environment. 553:650-661.
