High virulence of a naturally occurring entomopathogenic fungal isolate, Metarhizium (Nomuraea) rileyi, against Spodoptera frugiperda

Abstract

The fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), originates from the neotropics America and is a significant threat to maize cropping systems (Sparks, 1979).

Natural Prevalence, Molecular Characteristics, and Biological Activity of Metarhizium rileyi (Farlow) Isolated from Spodoptera frugiperda (J. E. Smith) Larvae in Mexico

“…In addition, the selection of a pathogen as a biocontrol agent requires that isolates be tested against an insect population from the locality in which the program is to be run [ 52 ]. In our study, 23 of the 24 M. rileyi isolates collected in the field and tested under laboratory conditions caused high rates of larval mortality (ranging from 80% to 98.7%), similar to studies performed on this pest in Colombia [ 24 ], India [ 26 ], and China [ 48 , 49 ].…”

“…A concentration of 1 × 10 6 or 1 × 10 7 conidia/mL of two M. rileyi isolates from China caused 50% mortality against the third instar of the same insect species we studied [ 49 ]. Similarly, LT 50 values of 5–7 days [ 24 ] and 12 days [ 48 ] for isolates from Colombia and China, respectively, were reported for the S. frugiperda second instars. In general, several factors can influence the susceptibility of insects to infection by entomopathogenic Hyphomycetes [ 67 ], including developmental stages of the host [ 53 ], cuticle sclerotization [ 68 ], and insect immune system [ 27 ].…”

“…This very low infection prevalence was attributed to the recent invasion of this insect in this country. In general, differences in the natural infection percentages may be due to different factors, including the number of collected larvae, incubation under laboratory conditions, and differences in the susceptibility of the insect host [ 42 , 48 , 49 ]. In addition, in field conditions, high humidity and high rainfall, as well as warm conditions, were very favorable for disease development in India [ 26 ].…”

“…One important step for the development of a fungal bioinsecticide resides in the selection of pathogenic and virulent candidate isolates [ 48 ]. In addition, the selection of a pathogen as a biocontrol agent requires that isolates be tested against an insect population from the locality in which the program is to be run [ 52 ].…”

Blastospores from Metarhizium anisopliae and Metarhizium rileyi Are Not Always as Virulent as Conidia Are towards Spodoptera frugiperda Caterpillars and Use Different Infection Mechanisms

“…It is a dimorphic fungus with yeast-like hyphal bodies and a filamentous growth phase [ 18 ]. Much less is known about M. rileyi compared to M. anisopliae , but recent advances in M. rileyi research have contributed to our knowledge of different aspects of this pathogen, and this species’ potential as an entomopathogen is indisputable [ 18 , 19 , 20 , 21 ].…”