Abstract
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.
Highlights
The diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), is one of the most destructive cosmopolitan pests of cruciferous crops
These results suggested that the effect of metaflumizone on the metaflu-SEL strain and the susceptible strain (SS)
The results showed that metaflumizone resistance in the UNSEL strain was unstable after 12 generations without exposure to metaflumizone (Table 3)
Summary
The diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), is one of the most destructive cosmopolitan pests of cruciferous crops. Because of the irrational use of chemical insecticides, P. xylostella has developed different levels of Insects 2020, 11, 311; doi:10.3390/insects11050311 www.mdpi.com/journal/insects. As a member of the new chemical class of semicarbazone insecticides, Metaflumizone blocks the sodium channels of insects by binding selectively to the slow-inactivated state of the channels, causing flaccid paralysis and the eventual death of the target insects [6,7,8]. Metaflumizone has been used to effectively control a wide range of pests [9]. As an Environmental Protection Agency (EPA) reduced-risk candidate, metaflumizone was registered by BASF Chemical Co. in China in 2009 to control P. xylostella and Spodoptera exigua (Lepidoptera: Noctuidae) on Brassica vegetables [10].
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