Isolation, identification and virulence of indigenous entomopathogenic fungal strains against the peach-potato aphid, Myzus persicae Sulzer (Hemiptera: Aphididae), and the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

Muhammad Imran Hamid,Samy Sayed,Mohamed Alkafafy,Sami Ullah,Abu Bakar Muhammad Raza,Nevien M Gaber,Muhammad Asam Riaz,Muhammad Asim,Muhammad Zeeshan Majeed

doi:10.1186/s41938-021-00500-8

Abstract

BackgroundAs different biogeographic strains and isolates of entomopathogenic fungi vary in their genetic, enzymatic and pathogenic characteristics, this study assessed the virulence of 2 indigenous strains of Beauveria bassiana (Balsam) Vuillemin and Metarhizium anisopliae (Metschn.) Sorokin (Ascomycota, Hypocreales: Clavicipitaceae), isolated from naturally infected insect cadavers, against the 3rd instar nymphs of Myzus persicae (Sulzer) (Hemiptera: Aphididae) and 3rd instar larvae of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) using leaf-dip and larval-dip methods, respectively.ResultsBoth fungal isolates exhibited considerable pathogenicity against M. persicae and S. frugiperda. Mortality in all bioassays was conidial concentration and exposure time dependent and increased significantly along with both factors (R2 = 0.86–0.99 for B. bassiana and 0.82–0.94 for M. anisopliae). Moreover, M. anisopliae isolate appeared more virulent to S. frugiperda larvae than B. bassiana isolate, while the later fungal isolate was more lethal to M. persicae nymphs than the former one. At the highest conidial concentration (1.0 × 109 conidia/ml), M. anisopliae caused maximum mean mortality of S. frugiperda (88%) and M. persicae (65%) and B. bassiana exhibited maximum mean mortality of S. frugiperda (76%) and M. persicae (94%). Moreover, probit regression analyses showed LT50 values for M. persicae of 4.57 and 6.86 days at 1.0 × 109 conidia/ml for the isolates of B. bassiana and M. anisopliae, respectively, while LC50 values were 7.75 × 106 and 8.70 × 107 conidia/ml after 10th day of application, for the isolates of B. bassiana and M. anisopliae, respectively, against M. persicae. Similarly, LT50 values for S. frugiperda were 7.75 and 7.03 days for 1.0 × 109 conidia/ml concentration and LC50 values were 2.84 × 107 and 8.84 × 105 conidia/ml at 10th day data for the isolates of B. bassiana and M. anisopliae, respectively.ConclusionOverall study results demonstrated the effectiveness of B. bassiana and M. anisopliae against M. persicae and S. frugiperda, respectively. However, field evaluations of these indigenously isolated promising fungal strains against these insect pests.

Highlights

As different biogeographic strains and isolates of entomopathogenic fungi vary in their genetic, enzymatic and pathogenic characteristics, this study assessed the virulence of 2 indigenous strains of Beauveria bassiana (Balsam) Vuillemin and Metarhizium anisopliae (Metschn.) Sorokin (Ascomycota, Hypocreales: Clavicipitaceae), isolated from naturally infected insect cadavers, against the 3rd instar nymphs of Myzus persicae (Sulzer) (Hemiptera: Aphididae) and 3 rd instar larvae of Spodoptera frugiperda
Virulence and pathogenicity of both indigenous isolates of B. bassiana and M. anisopliae were determined against laboratory-reared 3rd instar nymphs of M. persicae and 3rd instar larvae of S. frugiperda under laboratory conditions
Maximum nymphal mortality (94%) was exhibited by the highest concentration (1.0 × 109 conidia/ml) of B. bassiana recorded on 10th day of bioassay, while minimum aphid mortality (8–31%) was observed for the lowest concentrations (1.0 × 106 and 1.0 × 107 conidia/ml) on 3rd and 5th day of bioassay (Fig. 1)

Summary

Introduction

As different biogeographic strains and isolates of entomopathogenic fungi vary in their genetic, enzymatic and pathogenic characteristics, this study assessed the virulence of 2 indigenous strains of Beauveria bassiana (Balsam) Vuillemin and Metarhizium anisopliae (Metschn.) Sorokin (Ascomycota, Hypocreales: Clavicipitaceae), isolated from naturally infected insect cadavers, against the 3rd instar nymphs of Myzus persicae (Sulzer) (Hemiptera: Aphididae) and 3 rd instar larvae of Spodoptera frugiperda Aphids (Hemiptera; Aphididae) and armyworms (Lepidoptera; Noctuidae) are among the destructive and economically important insect pests throughout the world (Singh and Singh 2020). Fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is one of the economically important and notorious lepidopterous pests. It is native to tropical and subtropical Americas but has recently been dispersed to African and Asian countries including Pakistan (Gilal et al 2020). It infests more than 80 agricultural crops, rice, maize, cotton, millet, sorghum and sugarcane crops (De Groote et al 2020)

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