Studies on genetics, stability and possible mechanism of deltamethrin resistance in Phenacoccus solenopsis Tinsley (Homoptera: Pseudococcidae) from Pakistan

Sulfoxaflor resistance in Oxycarenus hyalinipennis (Costa) induces negligible cross-resistance to other tested insecticides: stability, risk assessment, and fitness cost

BACKGROUND

Oxycarenus hyalinipennis (Costa) (Hemiptera: Lygaeidae) is a polyphagous insect pest. In Pakistan, O. hyalinipennis is managed by using different insecticides, a major concern for cotton producers, and has developed resistance to many of these. Sulfoxaflor belongs to a newly released sulfoximine family that has high efficacy for controlling sap-feeding insect pests.

RESULTS

A sulfoxaflor selected-population (Sulfo-Sel-Pop) of O. hyalinipennis showed a 3064.92-fold level of resistance after continuous selection for 18 generations with sulfoxaflor compared to unselected population (UNSel-Pop). The Sulfo-Sel-Pop showed a reduction in resistance (from 3064.92 to 635-fold) without exposure for five generations, indicating unstable resistance to sulfoxaflor. Cross-resistance studies of the Sulfo-Sel-Pop revealed no or very low cross-resistance to triazophos (0.42 to 0.30-fold), deltamethrin (0.85 to 0.18-fold) and acetamiprid (1.16 to 4.86-fold) from G₄ to G₁₉ compared to the field population (Field-Pop). The mean value of realized heritability was 0.15 in the Sulfo-Sel-Pop (G₁₉ ). Significantly reduced relative fitness was determined in the Sulfo-Sel-Pop (Rf = 0.21) followed by Cross₁ [(Sulfo-Sel-Pop ♂ × UNSel-Pop ♀) (Rf = 0.58)]_, and Cross₂ [(Sulfo-Sel-Pop ♀ × UNSel-Pop ♂) (Rf = 0.70)] compared with the UNSel-Pop. The values of intrinsic rate of natural increase (r_m ), biotic potential (Bp) fecundity, egg hatching, and net reproductive rate (R0) were also significantly less in the Sulfo-Sel-Pop compared to UNSel-Pop.

CONCLUSION

A very high fitness cost, unstable resistance and no or very low cross-resistance in the Sulfo-Sel-Pop have great implications in designing effective strategies for managing insecticide resistance to O. hyalinipennis. © 2021 Society of Chemical Industry.

Inheritance mode and metabolic mechanism of the sulfoximine insecticide sulfoxaflor resistance in Oxycarenus hyalinipennis (Costa)

BACKGROUND

Dusky cotton bug (DCB), Oxycarenus hyalinipennis (Costa) (Hemiptera: Lygaeidae), is a key insect pest of cotton. It causes huge losses to cotton and many other economically important crops. Sulfoxaflor is a newly introduced systemic insecticide that is effective against many sap-feeding insect pests such as aphids, whiteflies and true bugs. The present study was designed to characterize the inheritance of sulfoxaflor resistance in DCB. Moreover, the role of synergists in reducing sulfoxaflor resistance in DCB was also assessed.

RESULTS

A field population of DCB has developed 1132.0-fold resistance to sulfoxaflor after 11 selected generations in the laboratory. Nonsignificant difference of reciprocal crosses was observed depending on the LC₅₀ (median lethal concentration) values (95% confidence intervals overlapped), suggesting an autosomal mode of sulfoxaflor resistance inheritance. The degree of dominance of 0.7 for F₁ (Sulfo-Sel Pop ♀ × Lab-Pop♂) and 0.6 for F₁ '(Sulfo-Sel Pop ♂ × Lab-Pop♀), respectively, suggested that sulfoxaflor resistance was incompletely dominant. According to the monogenic model, the number of genes involved to induce sulfoxaflor resistance revealed that sulfoxaflor resistance was polygenic in nature. The realized heritability (h² ) value for sulfoxaflor resistance was 0.2. The synergists experiment indicated that esterases were involved in the sulfoxaflor resistance mechanism in DCB.

CONCLUSIONS

The current results indicate that there is autosomal, incompletely dominant and polygenic inheritance of sulfoxaflor resistance in DCB. Our results would be helpful in delaying sulfoxaflor resistance against DCB in the field. © 2021 Society of Chemical Industry.

Biochemical Mechanisms, Cross-resistance and Stability of Resistance to Metaflumizone in Plutella xylostella

The diamondback moth, Plutella xylostella (L.) is an important pest of cruciferous crops worldwide. It has developed resistance to many conventional and novel insecticide classes. Metaflumizone belongs to the new chemical class of semicarbazone insecticides. To delay the development of metaflumizone resistance in P. xylostella and to guide insecticide use in the field, the biochemical mechanisms, cross-resistance spectrum, and stability of resistance to metaflumizone were studied in a laboratory-selected resistant strain (metaflu-SEL). Synergism tests with the carboxylesterase inhibitor triphenyl phosphate (TPP), the glutathione S-transferase depletor diethyl maleate (DEM), and the P450 inhibitor piperonyl butoxide(PBO) had no obvious effect on metaflumizone in the metaflu-SEL strain and the susceptible strain (SS) of P. xylostella, with synergism ratios that ranged from 1.02 to 1.86. Biochemical studies revealed that the cytochrome P450-dependent monooxygenase increased only 1.13-fold in the metaflu-SEL strain compared with the UNSEL stain; meanwhile, carboxylesterase and glutathione S-transferase activity showed no difference. These results suggest that these detoxification enzymes may be not actively involved in metaflumizone resistance. Furthermore, the metaflu-SEL population showed a moderate level of cross-resistance to indoxacarb (11.63-fold), but only very low cross-resistance to spinosad (1.75-fold), spinetoram (3.52-fold), abamectin (2.81-fold), beta-cypermethrin (0.71-fold), diafenthiuron (0.79-fold), chlorantraniliprole (2.16-fold), BT (WG-001) (3.34-fold), chlorfenapyr (0.49-fold), and chlorfluazuron (0.97-fold). Moreover, metaflumizone resistance decreased from 1087.85- to 1.23-fold in the metaflu-SEL strain after 12 generations without exposure to metaflumizone. These results are useful for formulating insecticide resistance management strategies to control P. xylostella and to delay the development of metaflumizone resistance in the field.