Enterococcus mundtii (JBC60 isolate) in the control of the fall armyworm: A new biocontrol possibility

Abstract

Productivity losses caused by pests and diseases result in economic damage worldwide. Despite the effectiveness of chemical control, these methods pose risks to the environment and human health, and their continued use can lead to the development of resistance in pests and pathogens. As a result, biological alternatives have gained prominence in the market, although the number of bacterial-based biological agents remains limited. This study aimed to prospect new bacterial isolates with potential to control insect pests, obtained through the insect-trapping method. Bacteria were isolated from dead larvae, and their insecticidal activity was evaluated. The genus identification and species approximation were performed through 16S rRNA barcoding sequencing, along with the characterization of the bacterial growth curve and its insecticidal activity over seven days. A total of 70 isolates were obtained, of which 10 inhibited the growth of Spodoptera frugiperda. The sequencing analysis identified these isolates as Enterococcus mundtii, Enterococcus gallinarum, Enterococcus casseliflavus, and Serratia nematodiphila. Among the active isolates, five showed a growth inhibition rate higher than 90 %, including E. mundtii, E. gallinarum, and E. casseliflavus. For further studies, the JBC60 isolate of E. mundtii was selected due to its high activity and its non-pathogenic nature to humans. The growth curve showed maximum growth at 12 h of cultivation (3.17 × 108 CFU/mL) and a maximum OD of 0.7214 at 6 h. The insecticidal activity demonstrated a growth inhibition rate above 90 %. Our results indicate that E. mundtii (JBC60) has high potential to become a biological control agent against Spodoptera frugiperda.