|Rinkevich, Frank - CORNELL UNIVERSITY|
|Hamm, Ronda - CORNELL UNIVERSITY|
|Scott, Jeffrey - CORNELL UNIVERSITY|
Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 23, 2006
Publication Date: June 1, 2006
Citation: Rinkevich, F.D., Hamm, R.L., Geden, C.J., Scott, J.G. 2006. Dynamics of insecticide resistance alleles in house fly populations from New York and Florida. Insect Biochemistry and Molecular Biology. 37:550-558. 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. The present study, conducted by scientists at Cornell University and USDA’s Center for Medical, Agricultural and Veterinary Entomology (Gainesville, Florida) was conducted to determine whether levels of permethrin resistance increase over the fly season and whether resistance declines in cooler months when pesticide pressure is relaxed. The work was done with flies collected from dairy farms in New York and Florida to see whether there were geographic differences in resistance patterns. Resistance in New York flies increased during the fly season when pesticide pressure was high, and then declined over the fall, winter and spring months, indicating that resistant flies have lower overwintering fitness. In contrast, resistance in Florida flies showed no such seasonality. In addition, the genetic makeup of resistant flies (resistance allele frequencies) differed widely between New York and Florida populations of flies. The results indicate that strategies for managing insecticide resistance may need to be adjusted for different regions of the US.
Technical Abstract: The frequency of insecticide resistance alleles for two genes (Vssc1 and CYP6D1) was studied in field collected populations of house flies from two different climates. While the frequency of these resistance alleles in flies at dairies from four states has recently been reported, there is no information on the relative change of these allele frequencies over time. House flies were collected during the 2003-04 season from New York and Florida before the first application of permethrin, during the middle of the field season, after the final application, and again the following spring (following months without permethrin use). Bioassay results indicated that homozygous susceptible and extremely resistant flies were rare, while moderately and highly resistant individuals were relatively common at all times in both states. The frequency of resistance alleles at the New York dairy rose during the season and declined over the winter, suggesting an overwintering fitness cost associated with these alleles. The super-kdr allele was detected for the first time in North America at the end of 2003. In Florida the frequency of the resistance alleles did not increase during the spray season or decrease during the winter, suggesting there is substantial immigration of susceptible alleles to the Florida dairy and no overwintering fitness cost associated with resistance alleles in this climate. The bioassay correlated well with the frequency of the Vssc1 and CYP6D1 resistance alleles in New York, but not as well in Florida. This suggests there may be a new resistance mechanism or allele evolving in Florida.