Location: Mosquito and Fly Research
2022 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 Objective 1, aging studies with modified Vavoua traps are underway in the large outdoor fly cage. Testing with laboratory-reared stable flies will commence later in the summer when temperatures are a bit cooler. Cooperators have been identified at two universities and studies will be underway later in the summer to determine if digital insect counters can be developed. Cooperators will be provided with insects so they can be digitally characterized.
In regard to Objective 2, work with the new house fly attractant continued slowly, with plans to add z-9-tricocene to the blend in the summer of 2022.
In regard to Objective 3, studies are underway to further select the best locations for primary and secondary trap placement sites. The study site is the University of Florida Horse Teaching Unit, which is close to our lab and will be well-stocked with horses on a routine basis. Fly populations are essentially nonexistent and will remain so until temperatures cool later in the summer.
Untreated fabric was suspended on wire cylinders of 2 sizes so that the fabric was either 1 or 2 inches from the surface of the cylindrical trap when the traps were placed inside of the cylinders. This was to determine how the fabric affected the attractiveness of the trap surface. The trap inside of the larger cylinder captured enough flies to indicate that the 2-inch space between the trap surface and the fabric was too large. Flies were apparently landing on the fabric and eventually finding their way to the top of the cylinder from which they then landed on and were captured by the sticky surface of the trap. The trap inside of the smaller cylinder rarely captured any flies. Apparently flies attracted to the device were reluctant to enter the inside of the cylinder to reach the trap. The next step is to try treated fabrics with arrays of openings so flies attracted to the traps will be killed before they can pass through the openings.
A novel electrophysiological assay was recently developed that can characterize the effects of current and candidate insecticides on the insect nervous system. While the system was developed to assess larval mosquito nervous systems, it has been recently optimized to assess the effects of novel insecticidal and repellent formulations on the house fly nervous system. We are currently investigating the potential use of this assay to evaluate the type and degree of insecticide resistance in house flies by using house fly strains with known pyrethroid-resistance mechanisms.
Selected repellent amides, which have been discovered and characterized as spatial repellents against Aedes aegypti mosquitoes, are currently being tested as repellents/insecticides against house flies. We are also evaluating the effects of selected terpenoids on house flies as potential insecticides and insecticide synergists.
Under Objective 4A, a method was developed to grow large numbers of house flies on a diet composed of sterilized wheat bran and pelleted calf feed (70% water) inoculated with 3E+06 live E. coli (strain K12) per gram of media. Eggs were chemically sterilized and sterile culture medium was obtained by two 95-min autoclave cycles spaced two days apart. Sterile eggs placed on sterile media produced no pupae but could be “rescued” by adding live E. coli at 0, 2 or 4 days after egg placement. Sterile eggs on media inoculated with the same quantity of dead (autoclaved) E. coli produced no pupae. Monoxenic pupal production was ~200 pupae/100 g of medium, which was about 70% of production with non-sterile controls. Research is in progress to kill the E. coli in late-stage larvae or young adults so the fitness of bacteria-free house fly adults can be assessed.
Under Objective 4B, three strains of Beauveria bassiana were passed through house fly hosts for 10 generations in an attempt to increase their virulence for flies. Ironically, bioassay results indicate that the selections resulted in lower virulence for flies, perhaps because they were not allowed to alternate between vegetative and pathogenic states. Bioassay methods on filter paper were improved by evaluating the effects of moisture and the porosity of the paper. Mortality was highest on wet papers with a pore size of <2.5 microns.
Under Objective 4C, selection for strains of Tachinaephagus zealandicus that perform well on Hydrotaea aenescens continued, with >40 generations of selection now complete; work in 2023 will concentrate on evaluating the fitness of T. zealandicus reared on either H. aenescens or Sarcophaga bullata hosts.
Accomplishments
1. A novel method for evaluating the effects of insecticides or repellent on house flies. ARS researchers in Gainesville, Florida, have developed a novel method for evaluating the effects of candidate insecticides or repellents directly on the fly house central nervous system. The neurophysiological output of this new method can be used to characterize the mechanism(s) of action of house fly control compounds, assess the dose-response of insecticides/repellents, and/or evaluate the level of insecticide resistance to currently utilized insecticides or repellents. The effects of select known house fly control compounds are currently being characterized to demonstrate the potential of this new assay. Hopefully, the new method will provide useful information about the mechanism of action and potency of various candidate insecticides and repellents directly on the house fly nervous system while simultaneously winnowing large candidate libraries of potential new insect control compounds.
2. Development of rapid and cheap assays to define the presence of genetic insecticide resistance (IR) in Musca domestica, a major pest and vector of disease in dairy and poultry operations. The common house fly is a nuisance pest and mechanical vector of disease in both dairy and poultry operations. It also has a long history of substantial resistance to commonly used insecticides. Genetic resistance markers that are associated with reduced pesticide efficacy in flies have been studied in the laboratory for almost 30 years, but this information has never been implemented to benefit agricultural producers due to the difficulty of the methods used for assessment and the costs of assessment. IR assessment in flies has thus remained an academic research pursuit and has been applied to positively impacted producers. ARS scientists in Gainesville, Florida, applied recent technological advances to develop tools and assays that allow rapid and cheap assessment of IR in flies. These assays reduce time and cost by about 80% when compared to existing methods and use equipment that is commonly available to local extension personnel. Taken together, these assays should allow more effective use of available control sprays or implementation of other methods when IR is strong.
3. New records of fly parasitoids in Pennsylvania. Insecticide resistance in nuisance flies has made it difficult to control these pests with pesticides. The most effective alternative is the release of naturally occurring parasitic wasps that attack the fly pupal stage. ARS researchers in Gainesville, Florida, working with scientists at Pennsylvania State University and the University of Florida conducted a survey and found that the most common species of parasitic wasps on Pennsylvania poultry farms are in the genera Spalangia and Trichomalopsis. These environmentally friendly wasps can now be raised commercially and sold to poultry producers to help them control flies without chemical pesticides.
Review Publications
Hinkle, N.C., Hogsette, Jr, J.A. 2021. A review of alternative controls for house flies. Insects. 12(11), 1042:1-18. https://doi.org/10.3390/insects12111042.
Burgess, E.T., Taylor, E.E., Acevedo, A., Tworek, M., Nayduch, D., Khurana, N., Miller, J.S., Geden, C.J. 2021. Diets of Erythritol, Xylitol and Sucrose affect the digestive activity and gut bacterial community in adult house flies. Entomologia Experimentalis et Applicata. https://doi.org/10.1111/eea.13088.
Campbell, C.B., Kline, D.L., Hogsette, Jr, J.A., Tenbroeck, S.H. 2021. Species complex of mosquitos captured by mechanical traps and an equine host. International Journal of Veterinary Science and Research. 7(2):169-177. https://doi.org/10.17352/ijvsr.000097.
Smythe, B., Zepeda, R., Hogsette, Jr, J.A. 2020. Establishing a method to evaluate the efficacy of compounds aimed at repelling horn fly (Diptera: Muscidae) infestations on cattle in a laboratory setting. Journal of Economic Entomology. 113:3011-3016. https://doi.org/10.1093/jee/toaa208.
Geden, C.J., Nayduch, D., Scott, J.G., Burgess, E.R., Gerry, A.C., Kaufman, P.E., Thomson, J., Pickens, V., Machtinger, E.T. 2021. House fly (Diptera: Muscidae): biology, pest status, current management prospects, and research needs. Journal of Integrated Pest Management. 12(1):39, 1-38. https://doi.org/10.1093/jipm/pmaa021.
Machtinger, E.T., Weeks, E.N., Geden, C.J., Lacher, E. 2022. Pests and parasites of horses. Complete Book, Wageningen Academic Publishers. 396 pgs. https://doi.org/10.3920/978-90-8686-923-7.
Xiong, X., Kelkar, Y.D., Geden, C.J., Zhang, C., Wang, Y., Jongepier, E., Verhulst, E.C., Gadau, J., Werren, J.H., Wang, X. 2021. Long-read assembly and annotation of the parasitoid wasp Muscidifurax raptorellus, a biological control agent for filth flies. Frontiers in Genetics. 12:748135. https://doi.org/10.3389/fgene.2021.748135.
