Research Project: Improved Surveillance and Control of Stable Flies, House Flies, and Other Filth Flies

Location: Mosquito and Fly Research

2023 Annual Report

Objectives
1. Develop strategies and technologies for more accurate and efficient surveillance and monitoring of adult stable flies. 1.A. Evaluation of commercially available stable fly traps from outside of the U.S. 1.B. Improved monitoring tools for long-range surveillance of stable flies. 2. Develop strategies and technologies for more accurate and efficient surveillance and monitoring of house flies. 3. Develop novel strategies and new products that lead to improved control and management of adult stable flies. 3.A. Development of trap-based management systems for stable flies. 3.B. Development of attract and kill devices for stable flies. 4. Develop novel strategies and new products that lead to improved control and management of house flies. 4.A. Effect of gut microbiome on fly fitness. 4.B. Beauveria bassiana for adult fly management. 4.C. Development of Tachinaephagus zealandicus as a biological larvicide.

Approach
Objective 1 will evaluate commercially available stable fly traps from outside of the US to determine which ones perform best in the US (Hypothesis 1.A. Commercially available stable fly traps from other countries could be valuable for improving US surveillance and trapping programs). It will also improve monitoring tools used for long-range surveillance of stable fly populations (Hypothesis 1.B. Improved monitoring tools will allow for surveillance of stable fly populations with minimal maintenance and servicing). Objective 2 will develop strategies and technologies needed for more accurate and efficient surveillance and monitoring of house flies (Hypothesis 2. A novel attractant based on constituents of molasses can be developed for house flies with no objectionable odor for indoor use). Objective 3 will develop trap-based management systems for stable flies which are more environmentally friendly than some of the current systems (Hypothesis 3.A. Localized stable fly populations can be maintained at sub-threshold levels by designing management programs based on strategically placed traps). It will also develop labor-saving attract and kill devices for managing stable flies (Hypotheses 3B. Attract and kill devices can be developed which produce substantial fly mortality but require a minimal amount of servicing). Objective 4 will investigate the effect of gut microbiome on fly fitness which could make the flies easier to kill with other management tools (Hypothesis 4.A. Axenic flies have lower fitness than non-sterile flies but can be “rescued” by ingestion of live bacteria). It will also re-visit Beauveria bassiana as a biological method adult fly management (Hypothesis 4.B. Screening wild isolates and subjecting candidate isolates to selection will result in faster-killing B. bassiana that is compatible with natural enemies). And finally, it will develop Tachinaephagus zealandicus, a parasitic wasp that attacks fly larvae, as a biological larvicide (Hypothesis 4.C. Hydrotaea aenescens can be used as production host for the gregarious larval endoparasitoid Tachinaephagus zealandicus).

Progress Report
In regard to Subobjective 1A trap aging and field studies are underway but have been delayed because of the absence of local field populations of stable flies. If the aging of traps changes their attraction to flies this cannot be determined without exposing them to field populations of flies. An aging study is underway at the Smithsonian National Zoo in Washington, DC, where flies are prevalent. Under Subobjective 1B research with counter development has progressed slower than expected mainly because of the schedules of the engineering cooperators. One cooperator has been looking at mosquito shapes to identify features which might be useful of for digitalized counting. The other is doing an assay of wing beat frequencies to determine if these can be detected digitally in a counter placed on a trap. Under Subobjective 2 after 4 years of adjusting the ratios of the 7 components in the attractant, a final composition was defined. Addition of the fly pheromone Z-9-tricosene at 0.1% increased fly collections by about 20%. A 10-X concentrate is shelf-stable and dilutes easily in water. Addition of surfactants (needed to capture and drown the attracted flies) such as Tween or Capsil had no negative effect on attraction. Tests with commercial traps showed the attractant performs well in common top-entry jar-style traps (e.g. Captivator). A more concentrated version of the attractant is needed for bottom-entry traps with mesh tops. Under Subobjective 3A animal defensive behaviors do indicate whether the numbers of traps needed to manage the flies are sufficient or additional traps are needed. This type of management system is fluid because it is necessary to add or remove traps at predetermined intervals depending on the host animals’ behavior. Easy to move traps are the best choice whether made of cloth or other materials. Under Subobjective 3B optimum size of openings in fabric was determined by cutting a series of openings in untreated screens and watching flies as they attempted to pass through. Opening size should allow the flies to pass through but not fly through. The idea is to allow the fly time to pick up a lethal dose of the pesticide on a treated screen before it passes through the opening. The optimum shape was a vertically oriented rectangle. Arrays of rectangular openings were cut in screen so that about 50% of the fabric was removed. Under Subobjective 4A methods to produce monoxenic fly pupae were improved by inoculating sterile media with E. coli. Surface sterilization of monoxenic pupae has proved to be challenging because of carry-over of E. coli within the puparium. In the final year of the project, we will emphasize treatment of monoxenic flies with antibiotics to eliminate bacteria carried over from the pupal stage. Under Subobjective 4B the experiments to improve virulence by selection for fast-killing strains of Beauveria bassiana have been completed. The relative susceptibility of house fly adults and the fly’s most important predator, Carcinops pumilio, was determined to be about 100-fold less for Carcinops than for flies when the insects walked on treated surfaces. Full immersion tests with both hosts narrowed the difference in susceptibility to 10X. Beauveria is now known to be compatible with both the parasitoids and predators of house flies. In another Beauveria study, infected flies were surprisingly effective at mitigating the effects of infection by resting on naturally warm surfaces. Under Subobjective 4C economical mass-rearing methods were developed for Hydrotaea aenescens. However, production yields were much lower for the parasitoid, Tachinaephagus zealandicus, when it was grown in H. aenescens rather than in Sarcophaga bullata. Sarcophaga bullata is therefore more economical for parasitoid production despite the higher cost of the liver required for their diet. Two T. zealandicus lines have been maintained for 60 generations on either H. aenescens or S. bullata. Work has begun to determine whether production metrics on H. aenescens have improved over this time.

Accomplishments
1. Compatibility of Beauveria bassiana with fly parasitoids. House fly (Musca domestica) populations have a negative impact on livestock and poultry and pose a risk to human and animal health. Biological control methods currently used include augmentative releases of pteromalid pupal parasitoids plus the application of Beauveria bassiana, a fungal entomopathogen. Scientists at Center for Medical, Agricultural, and Veterinary Entomology (CMAVE) in Gainesville, Florida, and Pennsylvania State University compared the efficacy of B. bassiana strains from field-collected muscid flies when applied to house flies and three species of filth fly parasitoids. The GHA strain of B. bassiana was also tested for comparative purposes. All strains isolated from muscid flies were more effective against house flies than GHA. Parasitoids were less sensitive to B. bassiana than the target flies. This research demonstrated that these two important biological agents (parasitoids and B. bassiana) are compatible as part of an IPM plan for fly management.

2. Mechanism of virus effects on house flies. House flies are a global pest of humans and their associated animals, transmitting pathogens and interfering with everyday activities because of annoyance. Pathogens that infect the flies themselves provide an attractive approach to managing these pests with fewer insecticide treatments. One of these pathogens is Salivary Gland Hypertrophy Virus (SGHV), which prevents female flies from mating successfully or developing their ovaries to produce eggs. At present, the mechanism that the virus uses to shut down mating behavior is unknown. This study, conducted by scientists at Center for Medical, Agricultural, and Veterinary Entomology (CMAVE) in Gainesville, Florida, and the University of Massachusetts, examined potential hormone therapies for reversing the effects of the virus on the flies to understand how the virus affects flies. None of the therapies was able to restore egg development in infected flies. However, virus-infected flies that were treated with the juvenile hormone methoprene became receptive to mating in spite of the infection. The results narrow down the mechanisms that the virus uses to sterilize flies and could lead to new approaches to fly management.

3. Blow fly development time is affected by larval diet. Lucilia cuprina, the Australian sheep strike blow fly, is responsible for enormous losses in the sheep industry because of the flies’ habit of laying eggs on the fleece of the animals’ hind area. Larvae then feed on dead and healthy tissue, causing skin and fleece to slough which often results in infection of the tissue by microbes. Larvae are also used medically for wound treatment in people, and their presence and age are important for determining the time of death at crime scenes. In this study, researchers in Egypt and at Center for Medical, Agricultural, and Veterinary Entomology (CMAVE) in Gainesville, Florida, compared fly development on three different larval diets: chicken meat, beef meat, and beef liver. Flies that developed on liver were less successful than those developing on beef or chicken, and development on liver took about 12% longer to complete. The results are useful for obtaining more accurate estimates for post-mortem intervals at crime scenes.

4. Genome of Nosema muscidifuracis. Nosema is a genus of intracellular microsporidian parasites of both pest and beneficial insects. Beneficial insects affected include honeybees, silkworms, and parasitic wasps of filth flies such as house flies and stable flies. Nosema disease results in an overall weakening of its host, shorter lifespans, and reduced fecundity. In this study, scientists at Auburn University (AL), the University of Rochester (NY), St Louis University (MO), and Center for Medical, Agricultural, and Veterinary Entomology (CMAVE) in Gainesville, Florida, examined the relatedness of several important species in this genus. In particular, the genome of N. muscidifuracis, a pathogen of filth fly parasitoids, was compared with other known Nosema species. N. muscidifuracis was found to be most closely related to Nosema species that infect honeybees. The phylogenetic and comparative analysis of Nosema will reveal novel insights into host-parasite interactions, enhance the understanding of parasite evolution, and enable genetic manipulation to improve disease management.

Review Publications
Xiong, X., Geden, C.J., Bergstralh, D.T., Werren, J.H., Wang, X., White, R.L. 2023. New insights into the genome and transmission of the microsporidian pathogen Nosema muscidifuracis. Frontiers in Microbiology. 14. https://doi.org/10.3389/fmicb.2023.1152586.
Dilling, S.C., Tenbroeck, S.H., Hogsette, Jr, J.A., Kline, D.L. 2023. Comparison of trap and equine attraction to mosquitoes. Insects. 14(4):374. https://doi.org/10.3390/insects14040374.
Ramirez, A., Gallagher, M., Geden, C.J., Stoffolano, Jr, J.G. 2023. Rescuing the inhibitory effect of the Salivary Gland Hyptertrophy Virus of Musca domestica on mating behavior. Insects. 14(416). https://doi.org/10.3390/insects14050416.
Pagac, A.A., Geden, C.J., Burgess, E.R., Riggs, M.R., Machtinger, E.T. 2022. Filth fly parasitoid (hymenoptera: pteromalidae) monitoring techniques and species composition in poultry layer facilities. Journal of Medical Entomology. 59(6):2006-2012. https://doi.org/10.1093/jme/tjac124.
Allan, S.A., Geden, C.J., Lanette, S.J. 2022. Laboratory evaluation of pupal parasitoids for control of the cornsilk fly species, Chaetopsis massyla and Euxesta eluta. Insects. 13(11). Article number 990. https://doi.org/10.3390/insects13110990.
Rajagopl, N.R., Bowman, A.R., Aldana, F.J., Batich, C.D., Hogsette, Jr, J.A., Kline, D.L. 2023. Semi-field evaluation of a novel controlled release device using transfluthrin as spatial repellent to prevent entry of mosquitoes into military tents. Current Research in Parasitology and Vector Borne Diseases. 3(100113). https://doi.org/10.1016/j.crpvbd.2023.100113.
Morales Ramos, J.A., Goolsby, J., Geden, C.J., Rojas, M.G., Garcia-Cancino, M.D., Rodriguez-Velez, B., Arredondo-Bernal, H., Ciomperlik, M.A., Simmons, G.S., Gould, J.R., Hoelmer, K.A. 2022. Production of hymenopteran parasitoids. In: Morales-Ramos, J.A., Rojas, M.G., Shapiro-Ilan, D.I., editors. Mass Production of Beneficial Organisms: Invertebrates and Entomopathogens. 2nd edition. San Diego, CA: Academic Press. p. 101-155.
Duvallet, G., Hogsette, Jr, J.A. 2023. Diversity, distribution, and phylogeny of stable flies (Stomoxys sp.). Diversity. 15:600. https://doi.org/10.3390/d15050600.
Lehmann, A., Brewer, G., Boxler, D.J., Zhu, J.J., Hanford, K., Taylor, D.B., Kenar, J.A., Cermak, S.C., Hogsette, Jr, J.A. 2023. A push-pull strategy to suppress stable fly (Diptera: Muscidae) attacks on pasture cattle using a coconut oil fatty acid repellent and attractant lures. Pest Management Science. 79(9):3050-3057. https://doi.org/10.1002/ps.7480.