Resistência de Tetranychus urticae (Kock, 1836) a acaricidas, em pessegueiro (Prunus persica (L.) Batsch) em Paranapanema e Jundiaí, SP

The study was carried out in order to evaluate the susceptibility to some acaricides in Tetranychus urticae (Koch, 1836) strains collected from peach orchards in Paranapanema and Jundiai counties, state of Sao Paulo, Brazil. The susceptible strain was collected from a native forest in Jundiai county, state of Sao Paulo. The slide dip method was used in this study. Mortality was assessed 48 h after treatment. Concentration-response lines and LC 50 s for the acaricides dimethoate, naled, mevinphos, cyhexatin, and propargite were estimated. The strain from Paranapanema orchard were 12.1-, 8.39-, and 6.08-fold more resistant to the organophosphates dimethoate, naled, and mevinphos, respectively, than the susceptible strain. In the case of the strain from Jundiai peach orchard, the highest resistance level was of 3.76-fold, observed for cyhexatin. In all other bioassays considering both strains, the resistance levels varied from 1.02- to 2.94-fold.