Location: Mosquito and Fly Research2012 Annual Report
1a. Objectives (from AD-416):
1. Provide better tools for surveillance and risk assessment by: studying house fly feeding behavior, resource location, and nutrition under field conditions; developing more efficient stable fly attractants; studying specific behaviors of adults; and determining the risk of introduction of Stomoxys species other than calcitrans and prioritize the risk of other potentially invasive fly species, including traps that sample across the entire population of adults and produce results with quantifiable error terms. 2. Develop more efficient integrated pest management by determining weaknesses within fly life cycles and matching these weaknesses to appropriate chemical control methods; and by developing biologically-based and bio-rational control methods. 3. Conceive and test applications of behavior-altering methods (e.g., behavior altering devices, attractants, repellents) for practical use, including repellents for livestock. 4. Determine the role of flies in dissemination of priority food safety pathogens including the role of some of the less-studied species of flies.
1b. Approach (from AD-416):
Nutritional attractants of house flies will be identified and new chemical lures for stable fly traps will be developed. Trapping data will be used to determine the risk of introduction of exotic Stomoxys spp. at ports in the southeastern U.S. Virus-based baits from candidate strains will be developed to control house flies. Systems for production of Diapriid parasitoids will be ready for transfer to commercial insectaries. These parasitoids can be effective for management of immature stable flies and house flies. New stable fly repellents for use on livestock will be evaluated in laboratory and field trials. Behavior-altering chemicals/surface combinations to repel and/or kill house flies will be evaluated in the laboratory with the aid of video monitoring and evaluation systems. An insecticide-based perimeter treatment method to provide protection against dispersing flies will be subjected to final field evaluations. The role of house fly in transmission of Salmonella enteriditis via contaminated poultry feed will be determined by exposing flies to contaminated feed and measuring their ability to transfer the pathogen to clean substrates.
3. Progress Report:
In large outdoor cages house flies were found to be more attracted to fresh calf manure than to any other feedstuff commonly found on dairy farms. Attractants that showed promise are not competing as well as expected when compared with optical attractants in field tests. Fly trapping is producing minimal results and trapping will continue for an additional year. Additional work with reducing agent drugs to improve the efficacy of salivary gland hypertrophy virus (SGHV) are encouraging but must be evaluated for safety and cost effectiveness. In large outdoor cages with natural foods present, releases of SGHV-infected flies into healthy populations did not lead to epizootics but instead stabilized at about 10% infection regardless of how many infected flies were released. A second year of sampling in the southeastern U.S. has been completed and selected parasitoid strains have been colonized in the insectary. An “improved sentinel” method was developed that allows highly efficient collection of large numbers of parasitoids from targeted sites. Additional collecting was done on beef cattle facilities in Nebraska in 2012; over 200,000 fly pupae were collected and are being held for parasitoid emergence. House flies fed the salivary gland hypertrophy virus (SGHV) were not becoming infected because the virus could not cross the peritrophic membrane that surrounded the virus in the gut lumen. However, by feeding the flies on chemical reducing agents, the gut became permeable and the flies became infected with the SGHV. A complete year of sampling in the southeastern U.S. has been completed and selected strains have been colonized in the insectary. Field evaluations of in-house and commercial attractant materials have been very positive. Studies are being conducted in 2 states in the U.S. and in 3 countries in Africa. Evaluation for attractive surfaces for house fly is more difficult than finding surfaces they do not prefer. However, evaluations with surfaces which are neither attractive nor repellent, but which are treated with a pesticide, have shown promise. Research with insecticide-impregnated targets has shifted to insect growth regulator-treated targets because house flies have become resistant to most of the pesticides registered for use. Flies pick up the growth regulator, pyriproxyfen, and pass it into the environment through their eggs, where it kills the immature stages of the fly. This controls flies in areas where pesticides cannot reach, and limits pesticide usage. This year, several new formulations were developed and tested, and three were tested in large cage studies. Results were very positive and further work is planned to improve the efficiency of transfer of the product to the flies in bait stations. Research on the role of house flies in transmitting Salmonella enteritidis has been delayed by the unexpected retirement of the poultry science collaborator; a new collaborator should be identified in the next few months.
1. Salivary gland hypertrophy virus of house flies. Flies prevent becoming infected from ingested pathogens by surrounding their gut contents with a protective, impermeable membrane. ARS researchers at Gainesville, Florida, improved the permeability of this membrane to salivary gland hypertrophy virus (SGHV) by giving the flies drugs that disrupt the membrane. This makes the flies more vulnerable to infection and the resulting knock-out of the fly’s reproduction. Results may lead to new methods for infecting flies with SGHV and other biocontrol agents that must be administered orally.
2. Parasitoids of stable flies and house flies. For many years there has been an ongoing debate over the best way to collect parasitic wasps that attack fly pupae on livestock farms. ARS researchers at Gainesville, Florida, developed a new method, the “improved sentinel station”, that allows collection of large numbers of wasps from closely targeted habitats. The new stations are highly sensitive and can be used to collect species that are rarely collected using traditional methods.
3. Color and contrast of insecticide-treated targets for stable fly management. When blue and black cloth targets were developed for use against tsetse flies, it was important to find blue cloth with pigments that would reflect sunlight in wavelengths most attractive to the fly. Using a target made of a blue cloth panel sewed to a black cloth panel was also considered important for maximum attraction. Recent work in Africa has shown that juxtaposition of blue and black cloth panels is not important and that black cloth worked fine by itself. ARS researchers in Gainesville, Florida, developing similar cloth panels to attract stable flies, needed to know if both cloth colors are necessary for maximum attraction. Capture rates for stable flies were not significantly different among blue/black, blue, or black cloth targets. Results will allow the use of targets of both colors or either color, depending on availability, cost, and desired use.
4. Insecticide-treated targets and flies as autodissemination vehicles for pyriproxyfen. ARS researchers at Gainesville, Florida, developing visual targets for a house fly attract and kill system, have switched from pesticides, to which most flies are resistant, to the growth regulator pyriproxyfen, an agent that blocks the development of immature fly stages so no adults are produced. When flies visit pyriproxyfen–treated surfaces, they carry the material with them and will deposit it when they lay their eggs, thus affecting the immature stages of other flies. Results could lead to development of self-treating stations and greatly reduce pesticide use.
Hogsette, Jr, J.A., Urech, R., Green, P.E., Skerman, A., Elson-Harris, M.M., Bright, R.L., Brown, G.W. 2012. Nuisance flies on Australian cattle feedlots: immature populations. Medical and Veterinary Entomology. 26:46-55.