Identification of native entomopathogenic fungi associated with Mahanarva fimbriolata Stahl in silvopastoral systems (Urochloa brizantha cv. MG-5 and Eucalyptus spp.)

Abstract

Abstract Background Pastures are susceptible to attacks from various species of insects, with Cercopidae being one of the main responsible pests. The species Mahanarva fimbriolata has a wide distribution in the Eastern region of Paraguay, leading to pasture damage. The most promising alternatives to chemical use are bioinsecticides, which could offer effective control while minimizing negative environmental impacts. Beauveria and Metarhizium have been documented as biocontrol fungi for Cercopidae insects. Therefore, identifying and isolating virulent native strains presents potential alternatives for controlling the spittlebug M. fimbriolata. Results Based on morphological and molecular characteristics, native strains of Metarhizium anisopliae and Beauveria bassiana were identified in the collected insects. Phylogenetic trees confirmed that the Beauveria sequence (Beauveria seq) obtained in this study aligned with the ARSEF 842 isolate of B. bassiana. The Metarhizium sequence (Metarhizium seq) was in the same clade as ARSEF 7450 and ARSEF 7487, which belong to the Metarhizium anisopliae. Beauveria bassiana displayed conidiophores that were broad at the basal part, forming synnemata or groups of conidiophores closely packed together, with a typical "zig-zag"-shaped rachis. The conidia were hyaline and smooth, ellipsoidal, and globose. On the other hand, M. anisopliae exhibited simple, straight conidiophores with bottle-shaped phialides. The conidia were elongated, ovoid to cylindrical, arranged in chains, and had an olive green color. Conclusions This is the first report of Metarhizium anisopliae and Beauveria bassiana obtained from nymphs and adults of Mahanarva fimbriolata in Paraguay.