Location: Mosquito and Fly Research
2020 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
ARS researchers at Gainesville, Florida, purchased Knight Stick and Vavoua traps in anticipation of testing in large outdoor cages. These traps are needed for evaluation of commercially available stable fly traps from outside of the United States. Current outdoor temperatures are too hot for daytime cage studies and these will be scheduled for later in the fall. Most of the supplies needed for long-range surveillance studies have been purchased and potential study sites will be investigated before the end of the fiscal year. Study sites have been narrowed down to two nearby locations. Candidate house fly bait solutions have been formulated and are ready for evaluations in large outdoor cages. However, because of hot, rainy weather conditions these evaluations have been scheduled for later in the fall. Some traps and other equipment needed for the stable fly trapping project have been purchased and the remainder will be purchased before the end of the fiscal year. Contacts will be made to narrow down the selection of study sites. All traps and equipment needed for the stable fly attract and kill project have been purchased. Arrangements for moving to the 2nd year of work will be begun if time permits.
ARS researchers at Gainesville, Florida, wrote a comprehensive review of house fly that will be the definitive work on this pest for at least the next decade. Written by a team of USDA and university scientists, the 124-page paper will be submitted before the end of FY2020. One ARS scientist at Gainesville, Florida, also used the time afforded by the maximum telework schedule to submit 8 refereed journal articles through ARIS, with 6 accepted as of July 17, 2020. Hundreds of house fly cadavers with potential Beauveria bassiana cadavers were screened, and 5 were confirmed by molecular genetic methods and propagated for further study. The relative virulence of the strains was compared against two benchmark strains (L90 and GHA). An attempt was also made to select for higher virulence in the new strains for 10 generations, and their relative compatibility with fly parasitoids was assessed. Work with the new house fly attractant was begun, and encouraging results were obtained in large rooms using a blend of 7 constituents. New colonies of Hydrotaea aenescens, Sarcophaga bullata, and Tachinaephagus zealandicus were established, and a mass rearing method developed for H. aenescens. Early results using H. aenescens as a mass-rearing host for T. zealandicus are encouraging, with production costs ($1.70 per 10,000 wasps) that economically viable for commercial development.
Accomplishments
1. Improved sampling method for fly parasitoids. Current methods for monitoring and collecting parasitoids from the field have advantages as well as major liabilities. Researchers in Gainesville, Florida, developed a novel approach that combines the advantages of both current methods. Fly larvae, along the rearing media in which they grow, were placed in the field and allowed to pupae in place. The new method, tested on cattle farms in Florida and Nebraska, returned far more parasitoids than the other two methods and provided a species composition profile that closely matched collections of wild pupae. This will benefit researchers and biocontrol businesses that must make periodic collections of these important biological control agents.
2. Practical guide to producing and testing Beauveria bassiana against house flies. Researchers often need to get new strains of Beauveria bassiana into culture and compare them with known varieties. Current methods for fungal isolation, growth, harvest, storage, and use in bioassays with house flies are scattered in different places in the scientific literature. Researchers at in Gainesville, Florida, developed a streamlined protocol of "how to" instructions for each step of the process. Examples of different types of bioassays are discussed, and data are presented showing the kinds of results that can be expected. The resulting paper provides a useful resource for researchers who are beginning to work with this important pathogen.
3. Novel insecticide shows promise for fly pests of livestock. Heavy reliance on chemical control has resulted in widespread resistance to the limited number of insecticides available for filth fly control. A team of researchers at Northern Illinois University, researchers at Gainesville, Florida, USDA-ARS Kerrville, Texas, Penn State University and Cornell evaluated the effectiveness of the novel insecticide Floralaner against house flies and horn flies. When it was fed to flies in a sugar bait, fluralaner was 23-fold more toxic than imidacloprid to a susceptible house fly strain and over 117-fold more toxic in an imidacloprid-resistant house fly strain. It also out-performed permethrin when it was applied directly to the flies. At present, fluralaner is only registered for use on dogs and cats for flea control. Our results indicate that this material would be very useful against insecticide-resistant flies.
4. Practical guide to conducting dose-response insecticide tests with house flies. Veterinary and medical entomologists who are involved in research on pest control often need to perform dose response bioassays and analyze the results. Researchers at Northern Illinois University and USDA-ARS-CMAVE in Gainesville, Florida, developed a step-by-step guide for doing this and provided instructions for using the free statistics program "R" for the analysis. Example bioassays and analyses are described using previously unpublished data from tests with house flies. Two kinds of assays are described. In the first, an insecticide (beta-cyluthrin) was applied topically. In the second, the insecticides spinosad and spinetoram were incorporated into sugar cubes and fed to the flies. Spinetoram was about twice as toxic as spinosad, and both were as effective against pyrethroid-resistant flies as against insecticide-susceptible flies. The results will be useful for new investigators who plan to conduct laboratory tests of insecticides against house flies. The results also indicate that spinetoram may be useful for controlling populations of insecticide-resistant flies.
5. Toxicity of chitosan for house flies, horse flies, and blow flies. House flies, horse flies and blow flies are important pests of humans and their associated animals. Scientists at the University of Massachusetts and researchers at Gainesville, Florida, examined the insecticidal properties of chitosan, a polysaccharide derived from chitin. Chitosan was fed to adult house flies (Musca domestica), horse flies (Tabanus nigrovittatus), and blow flies (Phormia regina) and found to be toxic to all three. The mode of action appears to be due to a disruption of the microorganisms that live in the gut of the fly. Chitosan is easily made, commercially produced, non-toxic to mammals, biodegradable, and used in a range of agricultural applications.
6. Virus infection makes flies lose their appetite. Previous studies have shown that the Musca domestica salivary gland hypertrophy virus (MdSGHV) dramatically enlarges the salivary glands and prevents or delays ovarian development in its adult host, the common housefly. The effect that this virus has on the fly’s natural food consumption, however, remained unexplored prior to this study, conducted by scientists at the University of Massachusetts and researchers at Gainesville, Florida. Both virus-infected and control flies were provided a choice of an 8% sucrose solution and a 4% powdered milk solution to determine food preferences. Healthy females with developing ovaries continued to consume a sugar and protein diet while infected females fed predominantly on a sugar diet. Infected flies of both sexes consumed less food than healthy flies. Infected flies in the field may spend less time visiting food sources, which could reduce the risk of pathogen movement.
7. Selecting for insecticide-resistant natural enemies of filth flies. Spalangia spp. are beneficial parasitic wasps that often are utilized to manage filth flies. They search for fly pupae in areas that might have been treated with insecticides, but nothing is known about whether they can develop tolerance or resistance to insecticides. The potential of S. cameroni to develop resistance to the commonly-used insecticide permethrin was determined and permethrin susceptibility was compared among several S. cameroni strains by ARS researchers at Gainesville, Florida. After 10 selected generations, susceptibility was significantly lower for the selected strain when compared to that of its unselected parent strain. Wasps from a commercial insectary colony were more susceptible to permethrin than strains collected more recently from the field. The results suggest that parasitoids can be selected for improved effectiveness in situations where insecticides are commonly used.
8. Beauveria bassiana is only effective against house fly larvae during a brief time window. The use of entomopathogenic fungi such as Beauveria bassiana to manage adult house fly populations has shown promising results, but little is known about whether it can be used against larvae. ARS researchers at Gainesville, Florida, demonstrated that temperature (22 versus 32°C) and media composition (diets with and without propionic acid) did not affect the effectiveness of B. bassiana treatments against fly larvae. Additional testing revealed that fly larvae are only susceptible to the pathogen when they are very young, and that very high fungal doses are required to kill them. The results show that B. bassiana should be used for adult fly control but that larval control with this biocontrol agent is prohibitively expensive.
Review Publications
Khater, H., Geden, C.J. 2019. Efficacy and repellency of some essential oils and their blends against larval and adult house flies, Musca domestica L. (Diptera: Muscidae). Journal of Vector Ecology. 44(2):256-263. https://doi.org/10.1111/jvec.12357.
Biale, H., Geden, C.J., Chiel, E. 2019. Heat adaptation of the house fly (Diptera: Muscidae) and its associated parasitoids in Israel. Journal of Medical Entomology. 57(1):113-121. https://doi.org/10.1093/jme/tjz152.
Burgess, E.R., Geden, C.J., Lohmeyer, K.H., King, B., Machtinger, E.T., Gaillard, E.R., Scott, J.G. 2020. The companion animal insecticide fluralaner outperforms industry-leading agricultural insecticides in resistant and susceptible strains of filth flies. Scientific Reports. 10(1):1-8. https://doi.org/10.1038/s41598-020-68121-z.
Stoffolano, J.G., Wong, R., Lo, T., Ford, B., Geden, C.J. 2020. Effect of chitosan on adult longevity when fed to Musca domestica L., Tabanus nigrovittaus Macquart, and Phormia regina (Meigen) adults and its consumption in adult Musca domestica L.. Pest Management Science. https://doi.org/10.1002/ps.5996.
Hogsette, Jr, J.A., Cilek, J.E. 2019. Evaluation of the DynaTrap FlyLight (DT-3009) against house flies, Musca domestica L., and stable flies (Diptera: Muscidae) under indoor conditions. Journal of Insect Science. https://doi.org/10.1093/jisesa/iez114.
Burgess, E.R., Geden, C.J. 2019. Larvicidal potential of the polyol sweeteners erythritol and xylitol in two filth fly species. Journal of Vector Ecology. https://doi.org/10.1111/jvec.12324.
