Abstract
ABSTRACT Due to the reduced host spectrum of the entomopathogenic fungus Metarhizium rileyi, its pathogenicity against different target insects must be assessed to develop biopesticides capable of controlling more than one pest species. This study aimed to evaluate the susceptibility of the pest species Chrysodeixis includens and Spodoptera frugiperda to different isolates of M. rileyi and, thus, determine a possible influence of the host of origin on the pathogenic activity of these isolates. Three isolates [CG1312 (C. includens as original host), CG381 (S. frugiperda as original host) and a new wild isolate (C. includens as original host)] were tested against larvae of C. includens and S. frugiperda, in third instar age, by treatment of surfaces with conidial suspension, under laboratory conditions. Both species were susceptible to the isolates of M. rileyi, with mortality rates of 53-58 % for C. includens and 74-84 % for S. frugiperda. The results suggest that the host of origin may not be determinant in the selection of pathogenic isolates of M. rileyi against these two pest insects.
Highlights
Chrysodeixis includens (Walker) and Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) are pest species of great economic importance in grain and fiber crops such as soybean, corn, bean and cotton (Pitre & Hogg 1983, Bueno et al 2011, Baldin et al 2014, Specht et al 2015).Traditionally, synthetic insecticides and genetically modified plants (Bt-crops) are among the main methods for controlling larval infestations
Three M. rileyi isolates were selected for this study: CG381 and CG1312, both from the invertebrate-associated fungal collection of the Embrapa Recursos Genéticos e Biotecnologia; and a wild isolate named Native, collected from C. includens cadavers in Sinop (Mato Grosso state, Brazil)
The larval mortality rates caused by the isolates at the end of the experimental period did not differ significantly for the C. includens (F2,27 = 0.23; p = 0.79) and S. frugiperda (F2,27 = 2.3367; p = 0.11) caterpillars
Summary
Chrysodeixis includens (Walker) and Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) are pest species of great economic importance in grain and fiber crops such as soybean, corn, bean and cotton (Pitre & Hogg 1983, Bueno et al 2011, Baldin et al 2014, Specht et al 2015). Synthetic insecticides and genetically modified plants (Bt-crops) are among the main methods for controlling larval infestations. The overuse of chemicals may result in damage to human and environmental health and cause the death of pollinators and natural enemies, in addition to selection of resistant pest populations Universidade Federal de Mato Grosso, Instituto de Biociências, Cuiabá, MT, Brasil
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