Molecular and Morphological characterization of multiple nucleopolyhedrovirus from Mexico and their insecticidal activity against Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), is the most important pest of maize in many countries. Entomopathogenic viruses mainly Baculoviruses family are excellent biological control agents and therefore a viable alternative for managing this pest. The aim of this study was to determine the biological activity of eight native nucleopolyhedrovirus (NPVs) against FAW larvae.Additionally, two of the most virulent isolates (SfCH32 and SfCH15) were characterized biologically by bioassays to estimate their median lethal dose (LD 50 ) and median lethal time (LT 50 ), morphologically by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and molecularly by restriction enzymes.Three (SfCH15, SfCH18 and SfCH32) of the eight tested native nucleopolyhedrovirus isolates caused mortalities ˃98% at 168-hr post-inoculation (hpi) with a dose of 9.2 × 10 4 OBs/larva. SfCH15 and SfCH32 isolates showed occlusion bodies (OBs) of irregular shape and size (1.02-2.24 μm). The SfCH15 and SfCH32 isolates showed similar median lethal dose (5.6 × 10 2 -6.4 × 10 2 OBs/larva). The lowest median lethal time (114.5 hpi) was observed with the SfCH15 isolate at the highest concentration (2.5 × 10 6 OBs/larva). The DNA restriction profiles for SfCH15 and SfCH32 were different, with their genome size being ~128,000 bp and 132,000 bp, respectively. SfCH15 and SfCH32 isolates showed similar morphological characteristics and the highest virulence against fall armyworm. This study showed that native isolates were highly virulent against S. frugiperda larvae, being similar to other reported strains; however, field studies are required to confirm their insecticidal effect. K E Y W O R D Sbaculovirus, biological control, fall armyworm, genetic variability, morphology, virulence

Growth inhibition of Spodoptera frugiperda larvae by camptothecin correlates with alteration of the structures and gene expression profiles of the midgut

“…Previous studies have been focused on finding control strategies such as various monitoring methods, correct identification of species and strains by genotyping, biological control and chemical application [5]. Effective insecticides for controlling S. frugiperda include pyrethroids, diacyl hydrazides, diamides, and benzoylureas [6]. Extensive application of insecticides caused problems including arise of populations with resistance to insecticides, toxicity to beneficial animals, and harmful effects on human health.…”

Evaluation of Commercial Virus Biopesticides for the Control of Moth Pests in Laboratory Conditions: The Cases of Thaumetopoea pityocampa and Helicoverpa armigera

“…During the last decade, many lab bioassays and field tests have been carried out, evaluating NPVs as biocontrol agents of lepidopteran pests with very promising results. NPVs have demonstrated effective insecticidal action against many notorious moth species, like H. armigera [32], Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) [33], Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) [34][35][36][37], Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) [38,39], Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) [40,41], and Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) [42,43].…”

The repository of biocontrol agents for Spodoptera frugiperda (Smith, 1797) with emphasis on their mode of action

“…In an experiment, three (SfCH15, SfCH18, and SfCH32) out of the eight tested isolates of native NPVs caused ˃98% mortalities at 168-h post-inoculation (hpi) with a dose of 9.2 × 104 OBs/larvae (Ordóñez- García et al, 2020). It accounts for the highest mortality recorded in the entomopathogenic virus (refer to Table 1).…”