Entomopathogenic fungi as endophytes for biological control of subterranean termite pests attacking cocoa seedlings.

Abstract:This study was conducted in the scope of developing a sustainable effective approach againstsubterranean termite pests using entomopathogenic and endophytic fungus-based biopesticides.Termites,Odontotermesspp. workers, were tested for their susceptibility to 15 entomopathogenicfungal isolates through the direct spraying of conidia suspensions at 1×108conidia/mL. In general,all the isolates screened were pathogenic, with 100% mortality 4–7 days post-inoculation. However,the most virulent isolates wereMetarhizium brunneumCb15-III; theM. anisopliaeisolates ICIPE 30and ICIPE 60;Hypocrea lixiiF3ST1; and theBeauveria bassianaisolates ICIPE 279, ICIPE 706 and ICIPE662. These isolates were further tested for their endophytic colonization of cocoa seedlings usingseed soaking, soil drench and foliar spray at 1×108conidia/mL. The colonization of the plant tissuesby the fungi was determined using a culture-based technique. Only theB. bassianaisolates ICIPE 706and ICIPE 279, andH. lixiiF3ST1 colonized the cocoa seedlings, with varied colonization rates amongisolates and inoculation methods. Three naturally occurring endophytes—Trichoderma asperellum,Fusarium solaniandF. redolens—were also isolated from the cocoa seedling tissues. These findingssuggest that cocoa seedlings are conducive to endophytic fungal growth either occurring naturallyor from artificial inoculation Our findings could possibly lead to an innovative approach tothe management of herbivory and subterranean termite pests in cocoa agroforests.