Survey on bromopropylate acaricide resistance in the citrus red spider mite, Panonychus citri and the effect of three synergists on its resistance

Biological characteristics of Panonychus citri such as life cycle, abundant progeny and arrhenotoky, have provided the pest a high potential to develop acaricidal resistance. Bromopropylate is recommended by Iranian Plant Protection Organization to control P. citri. In this study, resistance of p. citri to bromopropylate was investigated. Bioassay and synergists tests were performed with a Potter spray tower method. Results showed a resistance of 10.63 fold to bromopropylate in resistant population (RP). Pre-treatment of susceptible population (SP) of P. citri adult with the cytochrome P450 monooxygenase inhibitor, PBO, the esterase inhibitor, TPP, and glutathione-S-transferases inhibitor, DEM, increased bromopropylate toxicity by 5.58, 5.89 and 4.59-fold, respectively, while, these ratios were as 2.44, 2.51 and 2.38-fold, respectively, for RP. The overall lower synergism in RP compared with susceptible population by DEM, PBO and TPP suggests that glutathione-S-transferases, esterases and monooxygenase are not an important factor in resistance. The results of biochemical tests revealed that the activities of monoxygenase, α-naphthyl, β-naphthyl esterases and glutathione-S-transferase in the resistant population was 1.39, 1.70, 1.83, and 1.34- fold higher than that of susceptible population, respectively. Estimation of kinetic parameters showed qualitative changes in esterase and GST. The increased activities of detoxification enzymes may be caused by application of different acaricides which are used for control of this pest in citrus gardens. Therefore, other resistance mechanisms such as reduced penetration and target site insensitivity likely is involved in the resistance. Reduced bromopropylate application as well as application of acaricides with different mode of actions are necessary for avoiding resistance development.