Gut Endosymbiont Disruption through Antibiotics Influences the Metabolic Homeostasis in Spodoptera frugiperda (Lepidoptera: Noctuidae) Larvae

Fall armyworm as a polyphagous voracious feeder reported causing yield losses in most agriculturally important crops. As this insect had developed resistance against most of the insecticides, there is a need for an alternate approach to management. Gut endosymbiotic bacteria play a significant role in host feeding, digestion, and defense response throughout the life stages of insects. In the present study, we have isolated and identified the gut endosymbiotic bacteria of fall armyworm and the larvae were treated with antibiotics. The results showed that the maximum bacterial population was observed in the fourth instar of field-caught larvae and the least population was observed in the fourth instar artificially reared population. Based on the biochemical results the isolated gut endosymbiotic bacteria mainly comprised of Bacillus sp, Enterococcus sp., and Enterobacter sp. Based on the susceptibility of gut bacteria to different antibiotics, 6 antibiotic treatments with one insecticide treatment were administered to an artificial diet reared with third instar larvae and their dietary indices were evaluated. Among the antibiotic treatment, there was a reduction in the dietary indices in the larvae treated with Ciprofloxacin CIP5 (45.33%) and Cefotaxime CTX30 (41.73%) and an increase in dietary indices in the larvae treated with Nalidixin NA30 (31.58%), Doxycycline DO30 (8.82%), Vancomycin VA30 (22.05). Elimination of gut bacteria with a suitable antibiotic will affect the insect’s feeding and dietary indices subsequently decreasing the relative growth rate and insect’s physiology. Hence, gut bacteria-based green control measures might be used as an alternative approach for insecticides for the effective management of fall armyworm.