BASELINE SUSPCETIBILITY TO BIFENTHRIN IN MEXICAN POPULATIONS OF WHITEFLIES Trialeurodes vaporariorum (WESTWOOD) AND Bemisia tabaci (GENNADIUS) BIOTYPE B (HEMIPTERA: ALEYRODIDAE)

Abstract

Susceptibility to the pyrethroid insecticide bifenthrin was determined for two populations of Trialeurodes vaporariorum (Westwood): one from the state of Jalisco (T-JAL) and other susceptible from Texcoco, Estado de México (T-SUS); and for four populations of Bemisia tabaci (Gennadius) from the states of Tamaulipas (B-TAM), San Luis Potosí (B-SLP), Colima (B-COL), and a susceptible from Texcoco, Estado de Mexico (B-SUS). In T. vaporariorum, relative resistance values were 1.0 and 0.9X at CL50 and CL95 levels, respectively. In B. tabaci, relative resistance at CL50 level (RR50) ranged from 0.5 to 1.9X, while at CL95 level the relative resistance (RR95) ranged from 0.7 to 2.7X. All the tested populations are considered susceptible to bifenthrin. These values may be used as reference values in the future, in case those populations significantly change their response to bifenthrin. In T. vaporariorum and B. tabaci, susceptibility to bifenthrin is probably explained by the dilution effect caused by the wide use of neonicotinoid insecticides since 1991, which has reduced the selection pressure for resistance to bifenthrin.