The reproductive capacity of S. exigua is significantly reduced in Delta-SEL and Gos-SEL populations compared with the control group (SS-Strain). Elevation of the major detoxification enzyme cytochrome P450 monooxygenase and esterase might have an important role in inducing tolerance to deltamethrin in gossypol-fed S. exigua populations. This study enhances our understanding of detoxification enzyme pathways for S. exigua gene expression and their role in responses to insecticides and plant secondary metabolites. © 2018 Society of Chemical Industry.

Plants employ an intricate and dynamic defense system that includes physiological, biochemical, and molecular mechanisms to counteract the effects of herbivorous attacks. In addition to their tolerance to phytotoxins, beet armyworm has quickly developed resistance to deltamethrin; a widely used pyrethroid insecticide in cotton fields. The lethal concentration (LC50) required to kill 50% of the population of deltamethrin to gossypol-fed Spodoptera exigua larvae was 2.34-fold higher than the control group, suggesting a reduced sensitivity as a consequence of the gossypol diet. Piperonyl butoxide (PBO) treatment was found to synergize with deltamethrin in gossypol-fed S. exigua larvae. To counteract these defensive plant secondary metabolites, beet armyworm elevates their production of detoxification enzymes, including cytochrome P450 monooxygenases (P450s). Gossypol-fed beet armyworm larvae showed higher 7-ethoxycoumarin-O-deethylase (ECOD) activities and exhibited enhanced tolerance to deltamethrin after 48 and 72 h when compared to the control. Moreover, gossypol pretreated S. exigua larvae showed faster weight gain than the control group after transferring to a deltamethrin-supplemented diet. Meanwhile, gossypol-induced P450s exhibited high divergence in the expression level of two P450 genes: CYP6AB14 and CYP9A98 in the midgut and fat bodies contributed to beet armyworm tolerance to deltamethrin. Knocking down of CYP6AB14 and CYP9A98, via double-stranded RNAs (dsRNA) in a controlled diet, rendered the larvae more sensitive to the insecticide. These data demonstrate that generalist insects can exploit secondary metabolites from host plants to enhance their defense systems against other toxic chemicals. Impairing this defense pathway by RNA interference (RNAi) holds a potential to eliminate the pest’s tolerance to insecticides and, therefore, reduce the required dosages of agrochemicals in pest control.

, et al., RNA interferencemediated knockdown of a cytochrome P450 gene enhanced the toxicity of α-cypermethrin in xanthotoxin-fed larvae of Spodoptera exigua (Hübner), Pesticide Biochemistry and Physiology,

Spotted bollworm, Earias vittella, is one of the most serious and devastating insect pests of vegetables and cotton. Currently insecticides are necessary for its control in nearly all crop systems. In this paper we evalute the sub-lethal effects of lufenuron on biological traits and activity of detoxification enzymes; cytochrome P450 monooxygenases, esterase and glutathione S-transeferase (GST) in second instar larvae of E. vittella. Results showed that sub-lethal concentrations (LC15 and LC40 of lufenuron, prolonged larval period (at LC40 = 13.86±1.22 d, LC15 = 13.14±1.15 d, control = 12.28±0.7), pupal duration (LC40 = 11.1± d, LC15 = 11.8±0.28 d, control = 9.40±0.52) and extended mean generation time (LC40 = 27.3±0.43 LC15 = 29.0±1.19 d, control = 26.0±0.65). Sub-lethal exposure significantly prolonged the pre-adult stage, decreased pupal weight and reduced adult longevity in the parent (F0) and F1 generation. Moreover, the fecundity and egg viability were significantly lowered in parental and F1 generations at both sublethal concentrations compared to the control. While no significant effects were noted on reproductive parameters such as the intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R0) of F1 generation when compared to the control. Only mean generation time (T) in F1 at LC15 was significantly longer compared to the LC40 and control (LC40= 3.79±0.37, LC15 = 32.28±1.55d, control= 29.79±0.55). Comparatively, the activities of cytochrome P450 monooxygenases and esterase were higher than GST in treated populations.The increase in resistance development against insecticides may possibly because of elevated activity of detoxification enzymes. These results provide useful information for monitoring resistance in integrated pest management (IPM) programs for E. vittella.

, et al., Enhanced effects of dietary tannic acid with chlorantraniliprole on life table parameters and nutritional physiology of Spodoptera exigua (Hübner), Pesticide Biochemistry and Physiology,