Thermal response and horizontal transmission of cameroonian isolates of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae - Candidates for microbial controls of the banana root borer Cosmopolites sordidus

Beauveria bassiana and Metarhizium anisopliae are two promising microbial agents for biopesticides development against the banana root borer Cosmopolites sordidus. In this study, germination, mycelial growth, and sporulation of six local Cameroonian isolates of those two species were assessed under seven different thermal conditions (13, 15, 20, 25, 29 33, and 37 degrees C) to select thermo-tolerant isolates. The Transmission potential of the thermo-tolerant isolates was determined at 25 +/- 1 degrees C by dipping adult weevils in conidial suspensions (3.2 x 10(8)) conidia/ml and mixing these with uninoculated weevils in different proportions (0, 10, 30 and 50%), in groups of 30, and assessing the spread of the mycosis within the group over 35 d of co-incubation. Incubation temperature and isolates significantly affected germination, mycelial growth and conidial production. All isolates had large thermal tolerance ranges (13-33 degrees C) except MIITAC6.4.2 (20-29 degrees C). Horizontal transmission resulted in mortality of non-inoculated weevils from 4.63 +/- 1.77 to 53.3 +/- 11.9%. The isolate BIITAC6.2.2 exhibited high auto-dissemination potential and high conidia yield in cadavers. These results demonstrate the potential use of these isolates for biopesticides development against C. sordidus in Central Africa. (C) 2021 Elsevier Ltd and British Mycological Society. All rights reserved.