Entomopathogenic fungi as the microbial frontline against the alien Eucalyptus pest Gonipterus platensis in Brazil

Carolina Jordan,Mauricio Magalhães Domingues,Bianca Cristina Costa Gêa,Murilo Fonseca Ribeiro,Gabriel Moura Mascarin,Carlos Frederico Wilcken,Paula Leite Dos Santos,Leiliane Rodrigues Dos Santos Oliveira

doi:10.1038/s41598-021-86638-9

Carolina Jordan, Mauricio Magalhães Domingues + Show 6 more

Open Access

https://doi.org/10.1038/s41598-021-86638-9

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Abstract

The eucalyptus snout beetle (ESB), Gonipterus platensis, is endemic to Australia but has become a major invasive, destructive pest of Brazilian eucalyptus plantations. Efforts to develop insecticides based on entomopathogenic fungi against ESB are limited by the lack of known virulent strains. We therefore explored the virulence of indigenous Brazilian strains of major entomopathogenic fungi—Beauveria spp. and Metarhizium anisopliae—against ESB adults. We found widely varying virulence and later capacities for conidial production on infected adult cadavers. Two strains stood out, B. bassiana IBCB-240 and M. anisopliae IBCB-364, as especially lethal for ESB adults under laboratory conditions, sporulated abundantly on infected insects, and also outperformed comparable strains used in commercial mycoinsecticides. Notably, B. bassiana IBCB-240 exhibited lower LT50 values at low inoculum levels (≤ 107 conidia mL−1) and smaller LC50 values than M. anisopliae IBCB-364. Taken together, this study emphasizes natural variation in virulence among indigenous Beauveria and Metarhizium strains against ESB adults and identifies fungal strains with superior lethality to existing commercialized strains for managing this eucalyptus pest in Brazil.

Highlights

IntroductionIn Brazil, Eucalyptus plantations provide wood production to many kinds of industries (pulp and paper, siderurgy, fiberboard panels, biomass, etc.), and are cultivated on 5.7 million hectares (ha) with an average productivity of 36 m3 ha−1 annually[1]
In Brazil, Eucalyptus plantations provide wood production to many kinds of industries, and are cultivated on 5.7 million hectares with an average productivity of 36 m3 ha−1 annually[1]
Commercial mycoinsecticides based on Boveril and Metarril killed 60% and 52.1% of eucalyptus snout beetle (ESB) adults, while their unformulated strains, ESALQ-PL63 and ESALQ-E9, promoted mortality rates of 65.9% and 32.5%, respectively

Summary

Introduction

In Brazil, Eucalyptus plantations provide wood production to many kinds of industries (pulp and paper, siderurgy, fiberboard panels, biomass, etc.), and are cultivated on 5.7 million hectares (ha) with an average productivity of 36 m3 ha−1 annually[1]. Biological control is the key management strategy adopted for G. platensis control, using natural enemies such as the egg parasitoid Anaphes nitens (Hymenoptera: Mymaridae)[10], the predator Podisus nigrispinus (Hemiptera: Pentatomidae)[11] and entomopathogenic nematodes[12] In addition to these diverse biocontrol agents, entomopathogenic fungi are the largest commercially utilized microbial biocontrol agents in Brazil, but few effective fungal strains have been studied for use against ESB9. Based on their safety for humans and other non-target organisms[13], and their low risk to elicit insect resistance[14], entomopathogenic fungi are uniquely able to invade the host insects directly through the integument and can be used as an additional component in the integrated management toolbox against ESB in eucalyptus plantations. These commercial fungal strains may not be suitable or virulent enough to control ESB effectively and are not so used

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