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1 April 2013 Wide Spread Cross Resistance to Pyrethroids in Aedes aegypti (Diptera: Culicidae) from Veracruz State Mexico
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Seven F1 strains of Aedes aegypti (L.) were evaluated by bottle bioassay for resistance to the pyrethroids d-phenothrin, permethrin, deltamethrin, λ-cyalothrin, bifenthrin, cypermethrin, á-cypermethrin, and z-cypermethrin. The New Orleans strain was used as a susceptible control. Mortality rates after a 1 h exposure and after a 24 h recovery period were determined. The resistance ratio between the 50% knockdown values (RRKC50) of the F1 and New Orleans strains indicated high levels of knockdown resistance. The RRKC50 with α-cypermethrin varied from 10 to 100 among strains indicating high levels of knockdown resistance. Most of the strains had moderate resistance to (d-phenothrin. Significant but much lower levels of resistance were detected for λ-cyalothrin, permethrin, and cypermethrin. For z-cypermethrin and bifenthrin, only one strain exhibited resistance with RRKC50 values of 10- and 21-fold, respectively. None of the strains showed RRKC50 >10 with deltamethrin, and moderate resistance was seen in three strains, while the rest were susceptible. Mosquitoes from all strains exhibited some recovery from all pyrethroids except d-phenothrin. Regression analysis was used to analyze the relationship between RRKC50 and RRKC50. Both were highly correlated (R2 = 0.84-0.97) so that the slope could be used to determine how much additional pyrethroid was needed to ensure lethality. Slopes ranged from 0.875 for d-phenothrin (RRLC50fi01_959.gif RRKC50) to 8.67 for ë-cyalothrin (∼8.5-fold more insecticide needed to kill). Both RRLC50 and RRKC50 values were highly correlated for all pyrethroids except bifenthrin indicating strong cross-resistance. Bifenthrin appears to be an alternative pyrethroid without strong cross-resistance that could be used as an alternative to the current widespread use of permethrin in Mexico.

© 2013 Entomological Society of America
Adriana E. Flores, Gustavo Ponce, Brenda G. Silva, Selene M. Gutierrez, Cristina Bobadilla, Beatriz Lopez, Roberto Mercado, and William C. Black "Wide Spread Cross Resistance to Pyrethroids in Aedes aegypti (Diptera: Culicidae) from Veracruz State Mexico," Journal of Economic Entomology 106(2), 959-969, (1 April 2013).
Received: 20 July 2012; Accepted: 1 January 2013; Published: 1 April 2013

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