Mechanisms of deuteromycete fungal infections in grasshoppers and locusts: An overview

Several species of entomopathogenic deuteromycetous fungi can produce epizootics in populations of grasshoppers and locusts. Consequently there is considerable interest in development of these fungi as biocontrol agents. To this end we need information about the genetic and molecular basis of deuteromycete pathogenesis in acridids to develop a rational plan for strain improvement. Herein we present an overview of the infection processes of deuteromycetous fungi in acridids. These fungi penetrate through the cuticle which is composed primarily of proteins. Hydrophobic interactions, appressoria formation, and mucus production by the fungus are involved in fungal adhesion to the acridid cuticle. Extracellular proteases produced by Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metchnikoff) Sorokin solubilize cuticle proteins, which assists penetration and provides nutrients for further growth. Fungal infection through the locust gut is rare because indigenous gut microflora produce antifungal metabolites. Little is known of the events providing host specificity or those that lead to insect death once the cuticle is breached by the fungus; however, mechanical damage, nutrient deprivation, and toxic metabolites may be involved.