Location: Biological Control of Pests Research
2025 Annual Report
Objectives
1. Develop biorational insecticides and physical treatments for controlling invasive pest ants.
1.A. Discover naturally occurring compounds as active ingredients, attractants, repellants, and synergists for ant control.
1.B. Develop insecticide-free system for fire ant mound treatment.
2. Develop baiting systems for pest ant control.
2.A. Develop sustainable, water-resistant, specific, and cost-effective fire ant bait.
2.B. Develop bait station for controlling tawny crazy ants.
3. Identify, characterize, and utilize emerging infectious disease pathogens to control pest invasive ants.
3.A. Molecular and biological characterization of deformed wing virus in imported fire ants.
3.B. Determine the distribution of DWV and other honeybee related virus in imported fire ants and tawny crazy 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
Under Objective 1, we developed biorational insecticides and physical treatments for controlling invasive pest ants.
A device for attracting and killing fire ants without using insecticides was developed. An invention disclosure (Docket No. 0095.24) was approved by the ARS patent committee and a provisional patent application was filed on June 26, 2025. (U.S. Patent Application No. 63/830,679). Currently, synthetic insecticides remain the primary method for ant management. However, their resilience often leads to reinfestation after chemical treatments, necessitating repeated insecticide use. This overreliance raises concerns about environmental pollution and harm to non-target organisms. Most synthetic insecticides used in ant management are broad spectrum, impacting non-target species. There is an urgent need for environmentally friendly, specific, and sustainable products and methods for controlling invasive pest ants. This device provides an innovative and environmentally friendly option for reducing fire ant populations.
Geraniol esters were synthesized. C10–C18 fatty acid esters of geraniol have been identified by GC-MS analysis from the Dufour’s gland of red imported fire ants. While the Dufour’s gland in ants is commonly associated with trail-marking, nestmate recognition, and other pheromonal communications, the presence of these esters suggests potential roles in trail pheromone activity and colony-level signaling. Synthesizing these compounds and their analogues may provide valuable insights into their precise biological functions and support the development of novel behavioral disruptors or biochemical tools for fire ant management. To this end, we have synthesized geranyl octanoate, geranyl decanoate, geranyl undecylenate, geranyl dodecanoate, geranyl myristoleate, geranyl myristate, geranyl palmitate, geranyl stearate, and geranyl oleate.
Oregano essential oil and its major constituent-derived compounds were identified as promising repellents. Oregano essential oil, derived from Origanum vulgare, demonstrated potent repellency against both red imported fire ants and hybrid imported fire ants. This study highlights the potential of Oregano essential oil-particularly its abundant carvacrol content-and structurally related analogues as promising natural repellents for the effective control and management of imported fire ants.
New leads for toxicant development were identified. During this reporting period, we screened over 190 samples, including natural product-derived compounds and their synthetic analogues or derivatives, for activity against imported fire ants. Among the most promising leads were the natural sesquiterpene a-santalol, against hybrid imported fire ants, and the monoterpene carvacrol against red imported fire ants. Building upon these findings, we synthesized more than 20 structural analogues and derivatives. Several of these new compounds demonstrated enhanced toxicity, indicating strong potential for further development as effective toxicants.
A new moisture differential technique was developed to improve fire ant colony collection and maintenance. This method yields up to 52% more colony mass than the traditional water dripping method, with minimal brood loss. It provides a low-stress, efficient, and scalable approach for supporting laboratory research on imported fire ants.
Under Objective 2, we developed baiting systems for pest ant control.
A new bait carrier formulation was successfully developed. A Cooperative Research and Development Agreement (CRADA) with a California-based company was nearly finalized to support its commercialization. However, the CRADA process was paused due to anticipated incoming funds, which triggered the need for additional administrative review and coordination.
Under Objective 3, we identify, characterize, and utilize emerging infectious disease pathogens to control pest invasive ants.
The occurrence of deformed wing virus (DWV) in red, black and hybrid imported fire ants were determined for samples collected from more than 10 counties in Mississippi. The data shows that over 30% of sampled colonies were DWV positive. Both type A and B of DWV in fire ants have been sequenced. This work generated two publications.
The dynamics of Israeli Acute Paralysis Virus (IAPV) in fire ants were studied, focusing on both horizontal and vertical transmission of the virus within fire ant colonies. IAPV transmission from honey bee pupae to fire ants was confirmed. IAPV can be spread quickly across all fire ant developmental stages and persist across all fire ant developmental stages. Vertical transmission of IAPV from queens to eggs was suggested. The research clearly indicates that fire ants can act as an IAPV reservoirs, posing a threat to honeybee’s health. In addition, the virus was purified from infected worker ants and a research project was designed and planned to assess the virulence or genetical changes of IAPV in fire ants and to evaluate the potential risk of infecting honeybees.
At the request of USDA-ARS colleagues in Kerrville, Texas, volatile chemical profiles of the New World screwworm (NWS) were analyzed. The NWS is a highly destructive pest that causes severe wounds in warm-blooded animals and poses a major threat to livestock. Several female-specific compounds were identified for the first time, laying the groundwork for discovering NWS sex pheromones and attractants. These findings support the development of improved monitoring and control strategies for this economically significant pest.
Accomplishments
Review Publications
Chen, J. 2024. Chemical Characterization of Red Imported Fire Ants with Colony Development. Journal of Infectious Diseases. 2024;5(1):35-43.
Valizadeh Gever, B., Hardy, J., Chen, J., Amiri, E. 2025. Dynamics of israeli acute paralysis virus in red imported fire ant(solenopsis invicta buren) colonies. Journal of Invertebrate Pathology. 211(2025) 108310.
Abou-Shaara, H., Mehrparvae, S., Read, Q.D., Chen, J., Amiri, E. 2024. Impact of Commercial Plastic Queen Cell Cups on Rearing Success and Development of Honey Bee Queens. Journal of Apicultural Research. https://doi.org/10.1080/00218839.2024.2418682.
Zhu, Y., Du, Y., Liu, X.F., Portilla, M., Chen, J. 2024. Microarray and functional pathway analyses revealed significantly elevated gene expressions associated with metabolic resistance to oxamyl (vydate) in lygus lineolaris. Toxics. 12(3). Article 188. https://doi.org/10.3390/toxics12030188.
Ginson, G., Farhan, M., Abbas, A., Dileep, K., Noura, A., Lee, J., Chen, J., Khan, I.A., Xing, C. 2024. Stereoselective Oxidation of alpha-Copaene, a Fire Ant Repellent Sesquiterpene from Essential Oil of Dipterocarpus Turbinatus. Journal of Natural Products. https://doi.org/10.1021/acs.jnatprod.4c00758.
Ali, A., Shah, F.M., Khan, I.A. 2024. Toxicity and repellency of (e/z)-3-butylidenephthalide: a natural compound isolated from ligusticum porteri root extract evaluated against imported fire ants (hymenoptera: formicidae). Insects. 15,11,828.
Shah, F., Wang, M., Zhao, J., Lee, J., Manfron, J., Khan, I.A., Ali,, A., Farago, P.V. 2024. Insecticidal and repellent activity of piper crassinervium essential oil and its pure compounds against imported fire ants (hymenoptera: formicidae. Molecules. 29(22), 5430. https://doi.org/10.3390/molecules29225430.
Shah, F.M., Khan, I.A., Ali, A. 2025. A moisture differential technique: a new method for the separation and maintenance of the imported fire ant colonies in the laboratory. Scientific Reports. 30,15:3742. https://doi.org/10.1038/s41598-025-88116-y.
Chen, J., Ni, X., Grodowitz, M.J. 2024. Imported fire ants discard cricket eggs. Insects. 2024, 15, 954.
Liu, X.F., Miles, G.P., Zhu, Y., Grodowitz, M.J., Esmaeil, A., Scheffler, B.E., Chen, J. 2025. "Near-complete genome sequence of a type-A deformed wing virus discovered from Solenopsis invicta in Mississippi, USA". Microbiology Resource Announcements. February 2025 Volume 14 Issue 2.