Location: Biological Control of Pests Research
2021 Annual Report
Objectives
Objective 1: Discover new bioactive compounds and approaches to improve control of fire ants and other invasive ants.
Sub-objective 1A: Discover naturally occurring and environmentally benign synthetic compounds as toxins for invasive ant control.
Sub-objective 1B: Discover naturally occurring and synthetic compounds as behavior-modification agents for invasive ant control.
Objective 2: Develop new management strategies using genetic-based technologies for fire ant and invasive ant control.
Sub-objective 2A. Predict gene function and utilize existing genetic resources to test and develop invasive ant-specific assays, leading to control methods and products.
Sub-objective 2B. Develop gene disruption assays and approaches for mitigating the impact of invasive ants.
Sub-objective 2C. Identify and develop novel microbiome assays, and approaches for mitigating the impact of invasive ants.
Objective 3: Develop new and improved biorational pesticide delivery systems to control fire and other invasive ants.
Approach
Effective and environmentally benign ant toxins will be searched from various sources, including plants and other ants. In addition to ant toxins, we will search for behavior-modifying compounds that affect ant foraging and feeding using conventional bioassay-guided approaches and reverse chemical ecology approaches. These compounds can be very useful in improving ant developing control products. In the effort to develop gene disruption methods and materials, database comparisons will be conducted to identify target genes. Functional genomic techniques are essentially undeveloped in ants. We will begin by studying the genetics of key physiological processes within the colony. Because gene disruption experimentation is not standardized in ants, we will seek a visible phenotype, preferably non-lethal and visible in larvae, to provide an experimental positive control. We will initially focus on genetic disruption strategies which can disable the key physiological process of larval fitness and development. We will develop and utilize new molecular tools to validate, quantify, and develop genetic compounds and preparations that interfere with colony survival and resource exploitation. Additionally, preliminary studies identified unique viruses present in our regional populations of red imported fire ants. These discoveries need to be leveraged into ant-specific pathogens. The field of ant genomics and microbiome research has blossomed over the past 10 years. Individualized gene function studies, focusing on social form, chemosensory systems, neuropeptides, and oogenesis, have begun to shed light on the complex relationships between genes and phenotypes and behaviors. RNA interference studies have been performed on both fire ants and tawny crazy ants. A novel family of viruses was characterized. These investigations will lead innovation into new and improved control methods to mitigate invasive and destructive ants. Active ingredients or existing biorational pesticides will be used in developing new or improving existing biorational insecticide delivery systems. We will continue our effort in searching for adjuvants and synergists for improving the efficacy of mound treatment for fire ant control and spray treatment for tawny crazy ants. We will develop new water-resistant ant bait carriers using easily available local materials. Bait matrix will be developed and optimized for tawny crazy ants for both granular bait and liquid bait stations. Bait acceptance will be improved by using attractants and feeding stimulants. Bait selectivity will be enhanced by using selective repellants that attract targeted ants but repel non-targeted ants. We will continue our research on identifying effective synergists and surfactants for the final formulations.
Progress Report
Effort continued in searching for new naturally occurring ant toxins and behavior-modifying compounds from various natural sources. Two oxo fatty acids were identified from fire ant male alates, which were found to be fire ant attractants and feeding stimulants. A patent disclose was submitted and approved by the ARS patent committee for filing a patent application. A peer-reviewed paper titled “Natural occurring compounds/materials as alternatives to synthetic chemical insecticides for use in fire ant management” was published. Collaborated with scientists in University of Mississippi, a fire ant specific compound was identified and the effort on synthesis is ongoing. These works are related to the Objective 1 of the project (Discover new bioactive compounds and approaches to improve control of fire ants and other invasive ants).
An uncharacterized target gene expressed in larval stage was identified, which expected to produce lethal knockdown phenotype. Ant RNAi projects were reviewed and genes likely to interfere with knockdown are identified, which has been published. New genomic data on tawny crazy ants was examined for additional cross-referencing. Collaboration with Dovetail Genomics on a genomic project on tawny crazy ants is ongoing. The company provided a prize for this Genome Scaffolding project. Collaboration with MS State was initiated and samples of tawny crazy ants were collected and shipped to sequencing facility. A collection of insect virus sequences that have not been catalogued in GenBank was identified and the >1600 sequences have been translated, organized, and used to query ant transcriptomes. These analyses will identify patterns of virus types present in ants. A set of viruses identified in fire ant transcriptomes (from GenBank) were analyzed and published. These works are relative to Objective 2 (Develop new management strategies using genetic-based technologies for fire ant and invasive ant control).
Accomplishments
1. Fire ant attractants. Red imported fire ants are an important invasive pest that was inadvertently introduced into the United States from South America in the 1930s. The imported fire ants are estimated to be responsible for $6.3 billion cost annually in damage repair, medical care, and control costs in the United States. Bait is one of major techniques used in controlling fire ants. Fire ant attractants and feeding stimulants can be used to improve bait efficacy and enhance the bait selectivity by facilitating the finding and acceptance of the bait by ants. ARS researchers in Stoneville, Mississippi, identified two oxo fatty acids in the red imported fire ants. Behavioral bioassays using synthetic compounds showed that both oxo fatty acids are attractants to red imported fire ant workers. Fire ant workers preferentially fed on vegetable oil treated with these acids over the untreated vegetable oil. Since vegetable oil is the common food source used in most fire ant bait products, these two compounds can be used to improve the efficacy of existing fire ant bait products and develop new fire ant bait products.
Review Publications
Jin, Z., Chen, J., Wen, X., Wang, C. 2020. Effects of clay materials and moisture levels on habitat preference and survivorship of Formosan subterranean termite, Coptotermes formosanus. PeerJ. 8:e10243. https://doi.org/10.7717/peerj.10243.
Shi, Q., He, Y., Lei, Y., Qi, G., Chen, J., Lu, L. 2020. Thermally induced Actinidine production in biological samples. Journal of Agricultural and Food Chemistry. 68:12252-12258. https://doi.org/10.1021/acs.jafc.0c02540.
Du, Y., Zhou, A., Chen, J. 2021. Olfactory and behavioral responses of red imported fire ants, solenopsis invicta to ylang ylang oil and its components. Journal of Pest Science. https://doi.org/10.1007/s10340-020-01312-9.
Wen, C., Chen, J., Qin, W., Chen, X., Wen, J., Wen, X., Wang, C. 2020. Red imported fire ants (hymenoptera: formicidae) cover inaccessible surfaces with particles to facilitate food search and transportation. Insect Science. 28(6):1816-1828. https://doi.org/10.1111/1744-7917.12891.
Du, Y., Zhou, A., Chen, J. 2020. Olfactory and behavioral responses to acetate esters in red imported fire ant, Solenopsis invicta. Pest Management Science. https://doi.org/10.1002/ps.6152.
Xavier, C.A., Allen, M.L., Whitfield, A.E. 2021. Ever-increasing viral diversity associated with the red imported fire ant Solenopsis invicta (Formicidae: Hymenoptera). Virology Journal. 18:5. https://doi.org/10.1186/s12985-020-01469-w.
Chen, J., Oi, D.H. 2020. Natural occurring compounds/materials as alternatives to synthetic chemical insecticides for use in fire ant management. Insects. 11:758. https://doi.org/10.3390/insects11110758.
Wen, C., Chen, J., He, Y., Wang, F., Wen, X., Wang, C. 2020. Electrophysiological and behavioral responses of red imported red ants (Hymenoptera:Formicidae) to an essential balm and its components. Pest Management Science. https://doi.org/10.1002/ps.6225.
Allen, M.L. 2021. Prospects for using RNAi as control for ants. Frontiers in Agronomy. https://doi.org/10.3389/fagro.2021.591539.
Zhou, A., Du, Y., Chen, J. 2020. Ants adjust their tool use strategy in response to foraging risk. Functional Ecology. 00:1-12. https://doi.org/10.1111/1365-2435.13671.
Zhou, A., Du, Y., Riddick, E.W., Li, L., Chen, J. 2021. Behavioral and electrophysiological response of sugarcane aphids and imported fire ants to 2, 4, 6-trimethylpyridine, an alkaloid from the pink-spotted lady beetles. Journal of Pest Science. https://doi.org/10.1007/s10340-021-01363-6.
