Comparative analyses of the effects of sublethal doses of emamectin benzoate and tetrachlorantraniliprole on the gut microbiota of<i>Spodoptera frugiperda</i>(Lepidoptera: Noctuidae)

Laboratory assessments were conducted to evaluate the efficacy of seven ad-hoc approved insecticides, namely Chlorantraniliprole, Emamectin benzoate, Spinetoram, Thiodicarb, Chlorantraniliprole + Lambda-cyhalothrin, Emamectin benzoate + Lufenuron, and Novaluron + Emamectin benzoate, against Spodoptera frugiperda. These evaluations were carried out using a diet incorporation assay in a controlled laboratory environment with a temperature of 27 ± 1°C, relative humidity of 65 ± 5%, and a 12:12 (L:D) photoperiod. During the bioassay procedure, it is noteworthy that the doses of all tested insecticides were carefully administered within the minimum range of their recommended field rates. In acute toxicity trials, spinetoram had the greatest impact on reducing the survival of S. frugiperda. Similarly, corrected mortality was highest with spinetoram and lowest with thiodicarb. Additionally, chronic toxicity trials were conducted using life table response experiments (LTREs) in the F1 progeny of the group that had experienced acute toxicity. Extended development with the highest mortality was observed in spinetoram compared to other tested insecticides. Furthermore, life indices parameters like potential fecundity (Pf), natality rate (mx), intrinsic rate of increase (rm), net reproductive rate (mx) and finite rate of increase (λ) was greatly reduced in S. frugiperda treated with spinetoram compared with other insecticides specially thiodicarb. However, mean generation time (Tc), corrected generation time (τ) and the doubling time (DT) was prolonged in spinetoram compared with other tested insecticides. Furthermore, in sex ratio analysis, all tested insecticides, except for thiodicarb, led to a significant decrease in the proportion of females in the population of S. frugiperda. These findings strongly suggest the possible emergence of resistance in S. frugiperda against thiodicarb. Moreover, considering the endorsement of this insecticide by the Government of India through ad-hoc approval, farmers are likely to persist in its application. Hence, it is imperative to conduct further validation of these results, necessitating field evaluations for confirmation.

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The impact of carvacrol on the larval gut bacterial structure and function of Lymantria dispar

Yang,

Chen,

Zhang

2024

Front. Microbiol.

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IntroductionThe gut bacteria of insects play an important role in regulating their metabolism, immune system and metabolizing pesticides. Our previous results indicate that carvacrol has certain gastric toxic activity on Lymantria dispar larvae and affects their detoxification metabolism at the mRNA level. However, the impact of carvacrol on the gut bacteria of L. dispar larvae has been unclear.MethodsIn this study, the 16S rRNA sequencing technology was used to sequence and analyze the gut bacteria of the larvae which were exposed with sublethal concentration (0.297 mg/mL) and median lethal concentration (1.120 mg/mL), respectively.ResultsA total of 10 phyla, 16 classes, 47 orders, 72 families, 103 genera, and 135 species were obtained by using a 97% similarity cutoff level. The dominant bacterial phyla in the gut of the L. dispar larvae are Firmicutes and Proteobacteria. The treatment with carvacrol can significantly affect the structure of gut bacteria in the larvae of the L. dispar. At both doses, carvacrol can shift the dominant gut bacteria of the larvae from Proteobacteria to Firmicutes. At the genus level, two doses of carvacrol can significantly enhance the relative abundance of probiotic Lactobacillus in the gut of L. dispar larvae (p ≤ 0.01). Additionally, significant differences were observed among the five bacterial genera Burkholderia-Caballeronia-Paraburkholderia, Anoxybacillus, Pelomonas, Mesorhizobium (p ≤ 0.05). The analysis of α-diversity and β-diversity indicates that the treatment with carvacrol at two doses significantly affect the bacterial richness and diversity in the larvae. However, the results of functional classification prediction (PICRUSt) indicate that carvacrol significantly down-regulate 7 functions, including Energy metabolism, Cell growth and death, and up-regulate 2 functions, including Carbohydrate metabolism and Membrane transport. The network analysis indicates that the correlation between gut bacteria also has been changed. In addition, the insecticidal activity results of carvacrol against L. dispar larvae with gut bacteria elimination showed that gut bacteria can reduce the insecticidal activity of carvacrol against L. dispar larvae.DiscussionThis study provides a theoretical foundation for understanding the role of gut bacteria in detoxifying plant toxins and conferring pesticide resistance.

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Comparative analyses of the effects of sublethal doses of emamectin benzoate and tetrachlorantraniliprole on the gut microbiota ofSpodoptera frugiperda(Lepidoptera: Noctuidae)

Cited by 4 publications

References 63 publications

Gut bacterium Burkholderia cepacia (BsNLG8) and immune gene Defensin A contribute to the resistance against Nicotine-induced stress in Nilaparvata lugens (Stål)

Gut bacterium Burkholderia cepacia (BsNLG8) and immune gene Defensin A contribute to the resistance against Nicotine-induced stress in Nilaparvata lugens (Stål)

Ecotoxicological Impact of Ad-Hoc Approved Synthetic Insecticides on the Biological Performance of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

The impact of carvacrol on the larval gut bacterial structure and function of Lymantria dispar

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