Location: Biological Control of Pests Research
2020 Annual Report
Objectives
Objective 1: Discover new efficacious natural products, including fire ant-specific pathogens, for Integrated Pest Management (IPM) of invasive ant species.
Sub-objective 1A: Evaluate naturally occurring toxins for invasive ant control.
Sub-objective 1B: Evaluate entomopathogenic agents for invasive ant control.
Objective 2: Determine gene function and utilize existing genomic resources to develop gene disruption approaches for mitigating the impact of invasive ants.
Sub-objective 2A: Perform database comparisons to identify candidate genes for disruption.
Sub-objective 2B: Functionally characterize specific candidate genes targeted for disruption.
Objective 3: Improve existing and design new biopesticide delivery systems as part of Integrated Pest Management (IPM) programs for invasive ant species.
Sub-objective 3A: Enhance the efficacy of biopesticides by improving adjuvants and synergists.
Approach
Current practice for controlling invasive pest ants depends heavily on synthetic insecticides, which have hazardous impacts beyond their intended uses. New safer and more sustainable technologies are needed to improve pest ant management. This project plan describes research to develop new products for managing invasive ants, particularly the imported fire ant, Solenopsis invicta, and the tawny crazy ant, Nylanderia fulva. This research will focus on 1) identifying new biopesticides, including naturally occurring toxins and biological control agents; 2) identifying and characterizing targets and methods for gene disruption; and 3) developing and improving delivery systems to maximize the efficacy of newly developed and existing biopesticides. This research will produce innovative products and methods for managing invasive pest ants.
Progress Report
This is the final report for this project which was replace by project #6066-22320-010-00D, "Biology and Control of Invasive Ants." Refer to project #6066-22320-010-00D for additional information. All planned experiments were completed.
Substantial results were realized over the 4 years of the project. Two innovative analytical methods are developed and published, which greatly enhanced the discovery of natural toxins and ant semiochemicals. These new methods resulted in the identification of new pyridine alkaloids in fire ants and lady beetles and terpene and terpenoids in fire ants and several native ants. Several behavioral bioassays have been developed and published, which greatly enhanced the discovery of compounds that modify ant behaviors. A series of naturally occurring ant toxins, fire ant attractants, repellants and fumigants were identified. A compound was discovered that elicited fire ants to attack their nestmates, which indicates a possible new approach to control ants by chemically inducing self-destruction (Objective 1: Discover new efficacious natural products, including fire ant-specific pathogens, for Integrated Pest Management (IPM) of invasive ant species). Based on their environmental safety profiles, several naturally occurring toxins were selected in formulation development for fire ant mound treatment. The efficacy of formulations based on 2-tridecanone and hexyl benzoate were evaluated in the field and the results are promising. The efficacy of these formulations was enhanced by improving adjuvants and/or synergists. A series of adjuvants have been tested for their intrinsic toxicity against fire ants, which serves a foundation for selecting adjuvants in formulation development. In collaboration with industry partners, water resistant bait carriers were developed, which not only can improve the efficacy of current oil-based fire ant baits, but also make it possible to develop sugar water-based granule baits. Not like fire ants, many invasive pest ants prefer sugar solutions over oils, such as the tawny crazy ants. Unfortunately, many bait active ingredients are not water soluble. In order to use oil soluble insecticides in sugar water-based baits, surfactants are usually needed. Unfortunately, surfactants very often deter ant feeding. It was found that certain organic solvents, under certain concentrations, did not deter ant feeding. Such solvents can be used in sugar water to enhance the solubility of oil soluble insecticides. This has the potential to lead to the development of ant baits effective against many species of sugar-loving ants using oil soluble active ingredients (Objective 3: Improve existing and design new biopesticide delivery systems as part of Integrated Pest Management (IPM) programs for invasive ant species).
Two known ant viruses and four novel viruses were discovered in fire ant juveniles in the Mississippi Delta. Multiple reference-based assemblies of 6 sequenced (paired Illumina reads) samples of red imported fire ants were performed to identify these RNA viruses. Comparison of novel viruses to other ant transcriptome data suggested that the viruses were not contaminants but truly associated with ants. These discoveries were used to leverage collaboration with University scientists and more in-depth analyses and characterizations. As identified, a total of five virus sequences were submitted as Invention Disclosures to OTT. All were recommended for publication rather than patenting. An article in the April 2020 “Agricultural Research Partnerships (ARP) Network NOTES” publicized the availability of the novel RNA viruses infecting ants. These viruses can potentially be directly exploited or engineered for the biological control of fire ants (Objective 2: Determine gene function and utilize existing genomic resources to develop gene disruption approaches for mitigating the impact of invasive ants).
Accomplishments
Review Publications
Chen, J., Wang, L., Zhao, J. 2019. Pyridine alkaloids in the venom of imported fire ants. Journal of Agricultural and Food Chemistry. 41:11388-11395.
Allen, M.L. 2020. Near-complete genome sequences of new strains of Nylanderia Fulva virus 1 from Solenopsis invicta. Microbiology Resource Announcements. 9:e00798-19.
Du, Y., Grodowitz, M.J., Chen, J. 2019. Electrophysiological responses of eighteen species of insects to fire ant alarm pheromone. Insects. 10:1-15.
Chen, J. 2020. Evidence of social facilitation and inhibition in digging behavior of red imported fire ants, Solenopsis invicta. Insect Science. https://doi.org/10.1111/1744-7917.12781.
Du, Y., Grodowitz, M.J., Chen, J. 2020. Insecticidal and enzyme inhibitory activities of Isothiocyanates against Red Imported Fire ants, Solenopsis invicta. Biomolecules EISSN 2218-273X. 10(5):716.
