Susceptibility of Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) to Heterorhabditis sp. (Poinar), Steinernema feltiae (Filipjev) and isolates of entomopathogenic fungi

Abstract Background The weevils Cosmopolites sordidus (Germar), Metamasius hemipterus (Linnaeus) , and M. hebetatus (Gyllenhal) (Coleoptera: Curculionidae) form a complex of important pests of plantain crops, causing crop losses of over 60%. Using synthetic insecticides to control these insects has not been efficient; for this reason, the present study searched for using entomopathogenic fungi (EPF) and nematodes (EPN) as alternative control tools. Results Compatibility of 74 combinations among 30 native fungal isolates and two EPNs ( Steinernema feltiae and Heterorhabditis sp.) through inhibition tests was evaluated. It was found that the bacteria carried by Heterorhabditis sp. inhibited the growth of all fungi. In the biological test with EPF and EPN simultaneously against adults of C. sordidus, antagonistic interactions were observed when Heterorhabditis sp. was applied. Only the combination of the fungus strain B14 ( Beauveria bassiana) + the EPN, S. feltiae had synergistic effects with a mortality rate of (93.3%). Conclusions This study revealed that S. feltiae and B. bassiana (strain B14) showed a synergistic effect against adults of C. sordidus. This combination could be an excellent candidate for developing a highly efficient biopesticide prototype in further trials and, together with other strategies of integrated pest management has the potential to improve control of the banana weevil complex.