Laboratory selection, resistance risk assessment, multi-resistance, and management of Tetranychus urticae Koch to bifenthrin, bifenazate and cyflumetofen on cowpea.

ABSTRACT

BACKGROUND: Tetranychus urticae (T. urticae) Koch is an important pest of vegetable crops worldwide. In this study, bioassays were carried out to analyze the resistance risk, multi-resistance and management of T. urticae Koch to bifenthrin, bifenazate and cyflumetofen on cowpea. RESULTS: The resistance ratios of the adult T. urticae population to bifenthrin (G16), bifenazate (G12) and cyflumetofen (G12) were 31.29, 9.38 and 5.81, respectively. Realized heritability (h 2 ) analysis showed that, under a selection pressure of 50-90% mortality, the generations needed to increase 10-fold LC50 values of bifenthrin, bifenazate and cyflumetofen were 3.64-8.05, 5.75-12.71, and 10.93-24.15, respectively. No obvious multi-resistance among these three acaricides was observed. Synergist bioassay results showed that microsomal multifunctional oxidase (MFO) was involved in bifenthrin resistance of T. urticae, with a synergistic ratio of 22.38. However, MFO and GSTs were not the main factors conferring the resistance to bifenazate. MFO, glutathione S-transferases(GSTs), together with esterase contributed to the development of the resistance to cyflumetofen. Additionally, the toxicity selection index test showed that bifenazate was safe to the natural enemy Neoseiulus barkeri (N. barkeri) with a toxicity selection index (TSI) >484.85, while bifenthrin was the least safe (TSI = 0.92). CONCLUSIONS: These results demonstrated the T. urticae developed higher resistance risk to bifenthrin compared to bifenazate and cyflumetofen and no obvious multi-resistance among these three acaricides, providing guidance for designing appropriate strategies for the effective application of bifenthrin, bifenazate and cyflumetofen in the field and delaying the development of insecticide resistance. © 2019 Society of Chemical Industry.