[Aim]  To clarify the antimicrobial properties of the feeding secretions of red palm weevil, Rhynchophorus ferrugineus, larvae, and assess the effect of these secretions on various bacteria and fungi. [Methods]  The effects of aqueous extracts of sugarcane that had been consumed by R. ferrugineus larvae on four bacteria, and two fungi, species, and on the germination of fungal spores, were compared to those of freshly squeezed sugarcane juice. In addition, the effects of proteinase K and heat treatment on the antimicrobial activity of larval feeding secretions were determined. Finally, the antimicrobial activity of larval body surface secretions and excretions was tested to clarify the source of antimicrobial activity. [Results]  Compared to the control, sugarcane extract that had been consumed by larvae strongly inhibited the growth of Escherichia coli, Staphylococcus aureus, and Bacillus thuringiensis (P<0.000 1), and suppressed the germination of > 95% of Beauveria bassiana and Metarsiana anisopliae spores (P<0.000 1). However, it had no significant inhibitory effect on Serratia marcescens (P>0.05). Treatment with proteinase K and high temperature (100 ℃) did not affect the antimicrobial activity of larval feeding secretions, indicating that the active antimicrobial substances are not proteins or peptides. Larval body surface secretions and excretions not only did not inhibit the growth of E. coli and S. aureus, but promoted the growth of these two bacteria, indicating that the active antibacterial substances are probably secreted into the food during feeding. [Conclusion]  R. ferrugineus larvae secrete antimicrobial substances into food during ingestion that can effectively inhibit the growth of microorganisms. The antimicrobial compounds responsible have strong thermal stability. These results improve understanding of the strategies insects use to defend themselves against environmental pathogens, and lay a foundation for the development of insect-derived antimicrobial drugs.