Long-term field insecticide susceptibility data and laboratory experiments reveal evidence for cross resistance to other neonicotinoids in the imidacloprid-resistant brown planthopper Nilaparvata lugens.

Background: Long-term monitoring data is helpful to understand the fluctuation of susceptibility and pattern of cross resistance in insecticide resistance management. After the occurrence of imidacloprid resistance, the brown planthopper (BPH) has gradually developed resistance to thiamethoxam and clothianidin since 2010, but not to dinotefuran and nitenpyram. Here, we analyzed susceptibilities data of five neonicotinoids during 2005-2017 in East Asia and Vietnam to conduct cross-resistance patterns among neonicotinoids. To determine the factors of development of cross resistance in laboratory bioassays, we used the imidacloprid resistant and control strains that were selected from filed populations in the Philippines and Vietnam.
Results: The Linear Mixed Models (LMM) analyses of insecticide susceptibility data showed that the slope values of imidacloprid resistance effects were 0.68 and 1.09 for resistance to thiamethoxam and clothianidin, respectively. Laboratory bioassay results showed that the LD ₅₀ values for thiamethoxam and clothianidin in resistant strains (1.4-5.5 μg g ^-1 ) were 3.2-16.4 times higher than those in the control strains (0.28-1.5 μg g ^-1 ). However, the increase in the LD ₅₀ values for imidacloprid was not related to that for dinotefuran and nitenpyram based on the results of the LMM analysis and laboratory bioassay.
Conclusion: Our results demonstrate that the development of imidacloprid resistance result in strong-cross resistance to some neonicotinoids, thiamethoxam and clothianidin, but not to others, dinotefuran and nitenpyram. We anticipate that our findings will be a starting point for understanding mechanism of the different trend of cross resistance by analyzing long-term susceptibility data and laboratory bioassays in insect pests. © 2019 Society of Chemical Industry.
(© 2019 Society of Chemical Industry.)