Efficacy of native strains of entomopathogenic nematode, Heterorhabditis indica against the fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) from India

Abstract

Background The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a notorious polyphagous pest that has recently invaded India in 2018. Within a short period, this pest has spread throughout the country, causing a significant damage to maize. In order to manage this menace, farmers rely on chemical insecticides, but due to concealed feeding nature of this pest insecticides remain ineffective in reaching the target site. In this context, the present study aimed to isolate, characterize and evaluate the reproductive potential of the native strains of entomopathogenic nematode, Heterorhabditis indica against larval instars of S. frugiperda under laboratory conditions. Results Two strains of H. indica isolated and characterized from the rhizosphere of mango and curry leaf trees were designated as CICR-HI-MN and CICR-HI-CL, respectively. Both strains, CICR-HI-CL and CICR-HI-MN showed differential mortality against 3rd (LC50 value of 21.65, 48.91 IJs/larva), 4th (LC50 value of 25.46, 52.36 IJs/larva) and 5th (LC50 value of 59.20, 71.04 IJs/larva) instar larvae of S. frugiperda, respectively. The instar-wise mortality of S. frugiperda showed that 3rd instar was relatively more susceptible compared to 4th and 5th instar larvae. In terms of efficacy, CICR-HI-CL was almost twice effective than CICR-HI-MN when LC50 and LC95 values of 3rd instar larvae were compared. However, the reproductive potential of both the strains was significantly higher against 5th instar than the 3rd and 4th instar larvae. Strain CICR-HI-CL was more effective in larval mortality, while nematode reproduction was higher in CICR-HI-MN. Conclusions Native strains of H. indica evaluated in the present study were found effective against larval instars of fall armyworm, S. frugiperda. Higher reproduction on 5th instar larvae demonstrates the ability of these strains to multiply, sustain and perpetuate on late instars of this polyphagous pest and may serve as viable option in integrated pest management program.

Pathogenicity of entomopathogenic nematodes against the new invasive fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

“…On the other hand, FAW early instars were highly susceptible to H. indica infection and this obtained result was agreeable with that observed previously by (Acharya et al 2020;Lalramnghaki et al 2021;Shinde et al 2022). In confirmation to these findings, the lower nematode concentration against late larvae (5th and 6th instars) in our study caused lower mortality (≤ 50%); subsequently the recovery larvae after infection completed their development till pupation and/or adult emergence with wing deformation.…”

Potential of Entomopathogenic Nematode HbSD as a Candidate Biocontrol Agent against Spodoptera frugiperda

“…H. bacteriophora HP88 caused 65%, 95% and 85% mortality at concentrations of 100, 250 and 500 IJs per 5th instar larvae after inoculation for 4 days [ 24 ]. As shown in previous studies, two strains of H. indica showed differential mortality against 3rd stage larvae, with LC50 values of 21.65 and 48.91 IJs/larva, respectively [ 42 ]. Lalramnghaki et al studied four EPN species on S. frugiperda , with the LC50 value ranging from 20.26 to 35.08 IJs/larva at 72 h post-incubation for 3rd larval instars [ 43 ].…”