Molting Patterns and Mortality of Sphenarium purpurascens purpurascens (Orthoptera: Pyrgomorphidae) Inoculated with Metarhizium anisopliae

Abstract

The cuticle of insects that is periodically renewed through the process of ecdysis is a protective barrier against the external environment. It can confer resistance against entomopathogenic fungi, but few studies document how molting affects infection by entomopathogenic fungi. The research aimed to evaluate effects of molting on resistance by the Sphenarium purpurascens purpurascens Charpentier grasshopper, an important crop pest in México, to infection by entomopathogenic fungi. Two strains (6 MaEM and 9 MaEM) at four concentrations (1 × 10 5 , 1 × 10 6 , 1 × 10 7 , and 1 × 10 8 conidia per milliliter) of Metarhizium anisopliae Metchn. were used. Molts decreased as concentration of entomopathogenic fungi increased. Infection by entomopathogenic fungi at greater concentrations was faster, resulting in less time to kill after exposure to inoculum. More insects molted and survived at lesser doses of inoculum. Application of M. anisopliae at 1-week intervals is recommended against grasshopper early and late nymphal instars.