Resistance to lambda-cyhalothrin in Spanish field populations of Ceratitis capitata and metabolic resistance mediated by P450 in a resistant strain.

BACKGROUND: The withdrawal of malathion in the European Union in 2009 resulted in a large increase in lambda-cyhalothrin applications for the control of the Mediterranean fruit fly, Ceratitis capitata, in Spanish citrus crops. RESULTS: Spanish field populations of C. capitata have developed resistance to lambda-cyhalothrin (6-14-fold), achieving LC50 values (129-287 ppm) higher than the recommended concentration for field treatments (125 ppm). These results contrast with the high susceptibility to lambda-cyhalothrin found in three Tunisian field populations. We have studied the mechanism of resistance in the laboratory-selected resistant strain W-1Kλ (205-fold resistance). Bioassays with synergists showed that resistance was almost completely suppressed by the P450 inhibitor PBO. The study of the expression of 53 P450 genes belonging to the CYP4, CYP6, CYP9 and CYP12 families in C. capitata revealed that CYP6A51 was overexpressed (13-18-fold) in the resistant strain. The W-1Kλ strain also showed high levels of cross-resistance to etofenprox (240-fold) and deltamethrin (150-fold). CONCLUSION: Field-evolved resistance to lambda-cyhalothrin has been found in C. capitata. Metabolic resistance mediated by P450 appears to be the main resistance mechanism in the resistant strain W-1Kλ. The levels of cross-resistance found may compromise the effectiveness of other pyrethroids for the control of this species. © 2014 Society of Chemical Industry.

Cross-resistance to insecticides in a malathion-resistant strain of Ceratitis capitata (Diptera: Tephritidae).

Resistance to malathion has been reported in field populations of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), in areas of Spain where an intensive use of this insecticide was maintained for several years. The main goal of this study was to determine whether resistance to malathion confers cross-resistance to different types of insecticides. Susceptibility bioassays showed that the malathion-resistant W-4Km strain (176-fold more resistant to malathion than the susceptible C strain) has moderate levels of cross-resistance (three- to 16-fold) to other organophosphates (trichlorphon, diazinon, phosmet and methyl-chlorpyrifos), the carbamate carbaryl, the pyrethroid lambda-cyhalothrin, and the benzoylphenylurea derivative lufenuron, whereas cross-resistance to spinosad was below two-fold. The W-4Km strain was selected with lambda-cyhalothrin to establish the lambda-cyhalothrin-resistant W-1Klamda strain (35-fold resistant to lambda-cyhalothrin). The synergistic activity of the esterase inhibitor DEF with lambda-cyhalothrin and the increase in esterase activity in the W-1Klamda strain suggests that esterases may be involved in the development of resistance to this insecticide. Our results showed that resistance to malathion may confer some degree of cross-resistance to insecticides currently approved for the control of Mediterranean fruit fly in citrus crops (lambda-cyhalothrin, lufenuron, and methyl-chlorpyrifos). Especially relevant is the case of lambda-cyhalothrin, because we have shown that resistance to this insecticide can rapidly evolve to levels that may compromise its effectiveness in the field.