Resumen

BASTIDAS B, Danny M; CASANOVA L, Yngrid M  y  MOLINA DE FERNANDEZ, Darjaniva. Baseline susceptibility and synergistic effect to the insecticides malathion and pirmiphos-methyl in adults of Culex spp. Say, 1823 (Diptera: Culicidae) Mario Briceño Iragorry municipality, Aragua state, Venezuela. Bol Mal Salud Amb [online]. 2011, vol.51, n.2, pp.199-206. ISSN 1690-4648.

We evaluated the response to the organophosphorus insecticides malathion and pirimiphos-methyl in field populations of adult Culex spp. Mario Briceño Iragorry Municipality Aragua state. Bioassays were carried out using the bottles treated with insecticides. The time-mortality determination allowed us to obtain the baseline susceptibility of the insecticides evaluated. Diagnostic dose was defined as the lowest dose that kills the highest percentage of exposed insects. Survivors after 60 minutes of exposure to these doses was considered as resistance criterion defining this time, as the threshold of resistance. The mosquitoes were resistant to malathion at concentrations 0.1; 1 and 5 μg/mL with values of TL₁₀₀= 90; 90 and 75 minutes respectively and susceptible to pirimiphos-methyl at concentrations 1 and 5 μg/mL with values of TL₁₀₀= 30 and 15 minutes respectively, was obtained at the concentration 0.1 μg /mL TL₁₀₀= 75 which was not considered to be a low dose. The concentrations 5 μg /mL of malathion, 0.1 μg / ml of pirimiphos-methyl are suggested as a reference dose. Resistance mechanisms were identified with the synergist piperonyl butoxide (PB) at concentrations of malathion 1 and 5 μg/mL with FS = 2 and 2.5 respectively. Multifunction oxidase enzymes (MFO) play an important role in resistance to the insecticide malathion. The obtained results provide basic information for future monitoring programs of Culex spp, if necessary, due to its importance as a pest of tourist environments and as a vector of Filariasis (bacroftiosis) and West Nile Fever.

Palabras clave : Culex spp; organophosphorus; esterases; synergists; oxidases.