Histopathological changes induced in <i>Hypothenemus hampei</i> (Coleoptera: Curculionidae: Scolytinae) by infection with the entomopathological fungus <i>Metarhizium guizhouense</i> PSUM04 (Clavicipitaceae)

Abstract Metarhizium guizhouense (Clavicipitaceae) is an insect pathogen employed as a mycoinsecticide against many insect pests worldwide. In this study, for the first time in a laboratory setting, the pathogenicity of the M. guizhouense isolate PSUM04 was evaluated against the coffee berry borer, Hypothenemus hampei (Coleoptera: Curculionidae: Scolytinae). Following the exposure (1 × 10 9 spores/mL) of H. hampei to M. guizhouense PSUM04, morpho-histopathological changes and numbers of apoptotic cells via the TUNEL (terminal deoxynucleotidyl transferase (TdT), dUTP (deoxyuridine triphosphate) nick-end labelling) assay in H. hampei were evaluated at 12-hour intervals until 144 hours after exposure. The external morphology of H. hampei underwent drastic changes from 24 to 144 hours post-exposure accompanied by the degeneration of integument and adipose tissues. The semi-quantitative analytical score of TUNEL-positive cells showed a slight increase at 12 hours after exposure and a significant increase in TUNEL-positive apoptotic cells at 48 hours after exposure. These results suggest a series of tissue alterations of H. hampei during its process of infection with a strain of M. guizhouense , highlighting the pathogen’s potential as a biological control agent in natural settings.