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Title: Susceptibility of field-collected houseflies to spinosad before and after a season of use

Author
item DEACUTIS, J - CORNELL UNIVERSITY
item LEICHTER, C - CORNELL UNIVERSITY
item GERRY, A - UNIV. OF CALIFORNIA
item RUTZ, D - CORNELL UNIVERSITY
item WATSON, W - N. CAROLINA STATE UNIV.
item Geden, Christopher - Chris
item SCOTT, J - CORNELL UNIVERSITY

Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2007
Publication Date: 6/1/2007
Citation: Deacutis, J.M., Leichter, C.A., Gerry, A.C., Rutz, D.A., Watson, W.D., Geden, C.J., Scott, J.G. 2007. Susceptibility of field-collected houseflies to spinosad before and after a season of use. Journal of Agricultural and Urban Entomology. 23:105-110.

Interpretive Summary: House flies are important pests associated primarily with animal agriculture and are known to harbor numerous pathogens of animals and humans. Insecticides have been the mainstay of fly control programs for decades, and this has resulted in high levels of resistance to the commonly used products, especially permethrin and related pyrethoids. Spinosad is recently introduced insecticide for fly control that is thought to have a novel mode of action. The present study, led by scientists at Cornell University with University cooperators in several states and a scientist at USDA’s Center for Medical, Agricultural and Veterinary Entomology,Gainesville, Florida, was conducted to establish baseline susceptibility of fly populations to spinosad in various locations and to determine whether there was any evidence for resistance to this pesticide after a single season of use. There was inherent variation in fly susceptibility to spinosad among fly populations prior to the introduction of the pesticide as a product, however, there was no evident decrease in susceptibility after the first season of its use. The results demonstrate that spinosad can be a useful tool for managing populations of flies that are already resistant to other classes of insecticides.

Technical Abstract: Spinosad is a new and highly promising insecticide with a novel mode of action, and it was first available for house fly control in the United States in 2005. To maintain the effectiveness of this new insecticide, it will be important to monitor populations for the evolution of resistance. We compared three bioassay methods (topical application, residual exposure, and feeding) using laboratory strains of spinosad susceptible and resistant adult house flies. Topical application was the most reliable and efficient method for detection of spinosad-resistant individuals. Using this bioassay we evaluated house flies that were collected before spinosad use (in 2004 and 2005). We found significant differences in survival between dairies, suggesting there was inherent variability between house fly populations prior to spinosad use. We also evaluated field chouse flies from before and after one season of spinosad use (2005). There was no evidence spinosad resistance was evolving after one season of spraying.