Location: Imported Fire Ant and Household Insects Research
2020 Annual Report
Objectives
1. Conduct studies on fire ant biology to develop new and improved surveillance and control strategies as part of an integrated pest management program.
1.1. Develop natural enemies of fire ants as classical biological control agents or biopesticides by characterizing their life cycle, evaluating their effectiveness, determining host specificity, developing methods for production and release, and formulating as biopesticides.
1.2. Determine how irrigation affects fire ant bait efficacy.
1.3. Develop novel biologically-based fire ant control by identifying the behavioral and semiochemical underpinnings of fire ant mating flights and colony establishment.
1.4. Identify key biological processes in fire ant life stages that may be susceptible to disruption. (vacant Molecular Biologist)
1.5. Determine and quantitate fire ant traits that contribute to their ability to survive the harsh conditions associated with accidental transport over long distances and/or establishing and expanding infestations at the invasion front. (vacant Entomologist)
2. Develop new surveillance and control strategies for crazy ants and other invasive pest ants.
2.1. Employ metagenomics techniques and next generation sequencing technologies to discover potential natural enemies of the little fire ant.
2.2. Develop an effective baiting strategy for the control of tawny crazy ants.
2.3. Investigate the homology of pheromone systems that are well understood for S. invicta, but relatively unknown in the little fire ant and the tawny crazy ant.
2.4. Identify key biological processes of little fire ants and/or tawny crazy ants that can be exploited and developed as novel control methods. (vacant Molecular Biologist)
2.5. Determine and quantitate little fire ant, tawny crazy ant, and other ant species traits that contribute to their invasive success, e.g., metabolic rates. (vacant Entomologist)
Approach
1.1 Integration of any new natural agent into a fire ant control program will require the satisfactory completion of studies in host specificity, predicted-efficacy, virulence, mode of action/transmission, formulation/rearing and field release methodologies.
1.2 Water resistant and standard fire ant bait formulations exposed to irrigation will be evaluated for efficacy against fire ant colonies. The effect of bait application methods (piled vs broadcast) on improving bait tolerance to irrigation will also be assessed.
1.3 Behavioral and semiochemical underpinnings of fire ant mating flights and colony establishment will be examined by determining the behavior of alates to pyrazines with olfactometer bioassays and in-flight lek sampling. Male produced tyramides will be further evaluated for physiologicfal functions related to multiple mating and rapid wing loss.
1.4 The approach of this sub-objective will be defined by the scientist filling the vacant Molecular Biologist position.
1.5 The approach of this sub-objective will be defined by the scientist filling the vacant Entomologist position.
2.1 Little fire ants from across the native and introduced ranges will be collected and used as RNA source material to create cDNA expression libraries. Detailed bioinformatics analysis of resulting NGS data will allow us to identify potential microsporidia, fungi, viruses, protists, and non-hymenopteran eukaryotic parasites. Sequence leads will be verified by molecular analysis of little fire ant colonies sampled within and outside the native ranges.
2.2 Consumption and temporal feeding patterns by tawny crazy ants (TCA) on liquid sucrose bait containing a slow-acting toxicant will be compared to bait containing a fast-acting toxicant. Time lapse photography will be used to document temporal feeding patterns over 72 hours. TCA feeding patterns will be used to design liquid bait dispensers such as alginate hydrogel carrier and presented in a compostable dispenser.
2.3 Systematically evaluate exocrine glands in TCA and little fire ant (LFA) workers and queens for phenotypic effects, e.g. attraction, repellency, alarm, and recruitment using behavioral bioassays. Attraction will be investigated first, using a Y-tube olfactometer bioassay to guide the isolation of active compounds. Attractants can enhance baits and improve monitoring systems.
2.4 The approach of this sub-objective will be defined by the scientist filling the vacant Molecular Biologist position.
2.5 The approach of this sub-objective will be defined by the scientist filling the vacant Entomologist position.
Progress Report
Objective 1: Commercialization of a Red and Black Imported Fire Ant detection device was completed, and the kit should be available to stakeholders by late 2020. The device provides rapid identification of invasive fire ants and will be sold. The device provides a tool for regulatory agencies in the United States and other countries to enforce quarantine protocols. This progress significantly improves surveillance by detecting both quarantined fire ant species in a single, on-site test.
ARS researchers at Gainesville, Florida, have started research on a pheromone enhanced sticky trap fire ant surveillance system. Of twelve available sticky traps commercially available, only three successfully caught fire ant workers. ARS researchers at Gainesville, Florida, are now evaluating prototypes of a unique pheromone release system that controls the release rate and focuses the flow of pheromone vapor to the surface. Commercial pheromone traps target flying pest insects; however, target fire ants walk on/in a complex 3-dimentional surface, not addressed in currently available pheromone traps.
Solenopsis Invicta Virus-3 (SINV-3) is a natural control agent of imported fire ants that was successfully released in areas devoid of the pathogen, in California and Florida. Fire ants were exposed to either a bait or drench formulation containing purified virus. The pathogen was detected 3 and 6 months later in the treated areas, but not in adjacent control areas. Treated areas are being evaluated for infection sustainability and impact on the population. Four releases were conducted in Tennessee, but transmission and establishment never occurred. Further examination revealed a unique isolate of SINV-3 that may have co-evolved with the hybridization of the red and black fire ant species. Characterization of the new isolate, named Solenopsis Invicta Virus-3 Hybrid (SINV-3 Hybrid), is underway to determine traits of the virus that confer its host specificity.
Water resistant and standard fire ant bait formulations are being evaluated on sprinkler irrigated sod. This bioassay emulates nursery and landscape irrigation situations, which reportedly degrade the moisture sensitive fire ant baits, thereby decreasing bait efficacy. Laboratory studies compared the efficacy of piled versus scattered/broadcast applications of standard fire ant bait under irrigation conditions. Significant differences between the two treatments were not found. This result was unexpected because piled baits were hypothesized to be better protected from irrigation.
A patent has been issued on new fire ant active ingredients (AIs). These compounds effectively controlled colonies under laboratory conditions. ARS researchers at Gainesville, Florida, have successfully increased AI acceptability using pharmaceutical masking agents. The AIs have shown promise in controlling other pest insects (patent pending).
Objective 2: Field testing of an alginate hydrogel carrier for a liquid ant bait resulted in short-term reductions of tawny crazy ant populations. This hydrogel carrier is biodegradable, unlike other hydrogels, and is much easier to deploy than bait stations. Techniques are being developed to retard the desiccation of the liquid bait and extend the availability of bait to tawny crazy ants under field conditions.
Samples of the little fire ant were obtained from Florida, Hawaii, and Argentina to begin a survey of pathogens associated with this invasive ant for potential use as biocontrol agents. This ant is a problem in Hawaii, Guam, Australia, Israel, and many Pacific Island countries and territories. If eradication is not possible, biological control would be the only sustainable control strategy for little fire ants where they are well established.
Procedures were developed to dissect little fire ant workers’ Dufour’s and venom glands. Preliminary identification of chemical components has started. A bioassay has been developed to assess the effects of these extracts on workers.
Accomplishments
1. Natural spread of a virus in imported fire ants. Introduced from South America, the red imported fire ant currently infests over 128 million hectares of land in the United States and is estimated to cause damage exceeding $7 billion annually. Solenopsis invicta virus 3 (SINV-3) is an RNA virus specific for red imported fire ants that offers promise as a natural control agent. Scientists from Gainesville, Florida, and Florida A & M University conducted surveys to determine the prevalence of SINV-3 in winged female fire ants to understand the possible natural spread of the virus through mating flights. Collections were made from five urban areas and five adjacent rural areas of north Florida. SINV-3 was detected in winged females in nests from 7 of the 10 collection locations. The average infection rate of 44% was similar in rural and urban areas. Winged females were sampled because they mate aerially and disperse, founding colonies in new areas. Infected winged females may be the mechanism of SINV-3 spread throughout the fire ant community providing additional sustained control of fire ants in the U.S.
2. A super colony of invasive ants in Florida. The tawny crazy ant is an invasive ant from South America that infests Florida and Texas and is spreading to states along the Gulf Coast. Extremely large populations of this ant inundate urban and natural landscapes resulting in mass intrusions into buildings as well as reductions in biodiversity. Researchers in Gainesville, Florida, determined that tawny crazy ants did not fight with other tawny crazy ants from different nests located at the same site as well as nests located as far as 270 miles away. In fact, small fragments of colonies, including queens, from distant nests congregated together in the same nests in laboratory tests. This lack of aggressive behavior between widely separated colonies indicated that tawny crazy ants are not territorial over large areas. This supports the contention that tawny crazy ants in Florida are part of a super colony across the southern U.S. Lack of territoriality allows for the sharing of resources and movement of worker ants and brood between colonies, which can facilitate the spread of natural enemies such as pathogens and toxic baits being developed for their control.
Review Publications
Valles, S.M., Strong, C.A., Emmitt, R., Culkin, C., Weeks, R.D. 2020. Efficacy of the InvictDetectTM Immunostrip® to taxonomically identify the red imported fire ant, Solenopsis invicta using a single worker ant. Insects. 11(1):37. https://doi.org/10.3390/insects11010037.
Valles, S.M., Firth, A.E. 2020. Solinviviridae. Encyclopedia of Virology. https://doi.org/10.1016/B978-0-12-809633-8.21559-8.
Oi, D.H., Valles, S.M., Porter, S.D., Cavanaugh, C., White, G., Henke, J. 2019. Introduction of fire ant biological control agents into the Coachella Valley of California. Florida Entomologist. 100(1):284-286. https://doi.org/10.1653/024.102.0156.
Lawson, K.J., Oi, D.H. 2020. Minimal intraspecific aggression among tawny crazy ants (Hymenoptera: Formicidae) in Florida. Florida Entomologist. 103(2):247-252. https://doi.org/10.1653/024.103.0215.
Cha, D.H., Skabeikis, D.D., Collignon, M.R., Siderhurst, M.S., Choi, M.Y., Vander Meer, R.K. 2019. Behavioral response of little fire ant, Wasmannia auropunctata (Hymenoptera: Formicidae), to trail chemicals laid on epiphytic moss. Journal of Insect Behavior. 32:145-152. https://doi.org/10.1007/s10905-019-09721-0.
Ahn, S., Corcoran, J., Vander Meer, R.K., Choi, M.Y. 2020. Identification and characterization of GPCRs for Pyrokinin and CAPA peptides in the brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae). Frontiers in Physiology. 11:559. https://doi.org/10.3389/fphys.2020.00559.
