HIGHER DIPTERA PESTS OF LIVESTOCK, POULTRY, AND HUMAN HEALTH: INTEGRATED PEST MANAGEMENT AND ADULT BIOLOGY
Location: Mosquito and Fly Research Unit
Title: Pyriproxyfen and house flies (Diptera: Muscidae): effects of direct exposure and autodissemination to larval habitats
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2012
Publication Date: May 11, 2012
Citation: Geden, C.J., Devine, G.J. 2012. Pyriproxyfen and house flies (Diptera: Muscidae): effects of direct exposure and autodissemination to larval habitats. Journal of Economic Entomology. 49(3):606-613.
Interpretive Summary: House flies continue to be major pests of livestock, poultry and humans throughout the world. Fly control is a difficult matter in part because of the rapidity with which house flies have developed resistance to insecticides that are used to control them. Another challenge is the wide range of larval breeding sites that the flies can use, making it difficult to control them before the adult fly emerges. In the past few years there have been some successful uses of the insect growth regulator (IGR) pyriproxyfen for the control of other flies, including mosquitoes. Pyriproxyfen is a mimic of insect “juvenile hormone”, and when it is applied to larval breeding sites the insects become stuck in the immature stages and never become adults. In this paper, scientists with USDA’s Center for Medical, Agricultural and Veterinary Entomology (Gainesville, FL) and an Australian public health agency examined the potential of pyriproxyfen for house fly control. House fly larvae were highly sensitive to this IGR when it was applied to larval rearing medium. Wild flies from the field were as sensitive as flies from an insecticide-susceptible colony. The greatest promise for this material may be via the autodissemination approach, in which adult flies are treated in a way that allows them to transport pyriproxyfen to egg-laying sites. When gravid females were treated with a dust containing the IGR and then allowed to lay their eggs on larval medium, all of the resulting fly immatures died in the pupal stage. This approach would eliminate broadcast application of the insecticide and instead take advantage of fly behavior to deliver small amounts of the IGR to target sites where larval breeding is occurring.
Adult house flies (Musca domestica L.) that were exposed as young flies to filter paper (3.75 % a.i.) or sugar (0.01-0.1 %) treated with pyriproxyfen produced significantly fewer F1 pupae than untreated flies but adult emergence success from pupae was unaffected. In contrast, treatment of larval rearing medium (volume = 400 cm3, surface area = 85cm2) containing fly eggs with 3 ml of liquid pyriproxyfen solutions had no effect on pupal production but resulted in almost complete inhibition of adult emergence at the lowest concentration tested (0.0012%, or 12 ppm). There was little difference in susceptibility between an insecticide-susceptible and a wild strain of house fly. Dust formulations in diatomaceous earth were prepared from three commercial pyriproxyfen products and applied to the rearing medium, using 0.5 g of dust per assay container. The concentration that resulted in 50% inhibition (LC50) of adult fly emergence was 8-26 ppm, with little difference among the three products. Gravid females that were force-dusted with a pyriproxyfen formulation and allowed to oviposit produced significantly fewer pupae than untreated control flies at all concentrations greater than 0.5% and no adults at concentrations greater than 0.05%. When gravid females had a single 1-hour exposure (mainly tarsal contact) to 5% pyriproxyfen dust-treated cotton muslin fabric (6 mg/cm2) and were then allowed to oviposit, sufficient pyriproxyfen was transferred to reduce adult emergence success. When gravid females were allowed to make intermittent contact with treated fabric over 2 days and then allowed to oviposit, adult production was reduced by 63-76%. Results demonstrated that house flies can be used as autodissemination vehicles for pyriproxyfen if improvements can be made in formulation and treatment station design.