Efficacy of Thai indigenous entomopathogenic nematodes for controlling fall armyworm (Spodoptera frugiperda) (J. E. Smith)(Lepidoptera; Noctuidae)

Abstract

Background Under laboratory and greenhouse conditions, the virulence of 2 isolates of Thai indigenous entomopathogenic nematodes (EPNs) in controlling the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera; Noctuidae), was demonstrated. Six EPNs dosages were tested against 2 larval instars of FAW under the laboratory conditions, while 2 different concentrations were tested under the greenhouse conditions. Results The results of a laboratory experiment revealed that 2 Thai indigenous EPNs isolates (Heterorhabditis indica isolate AUT 13.2 and Steinernema siamkayai isolate APL 12.3) were efficient against the FAW, 2nd and 5th larval instars. Six different nematode concentrations (50,100, 150, 200, 250 and 300 infectious juveniles (IJs) ml−1) were evaluated, and all were proven to be effective, with the mortality rate associated with concentration. Inoculated larvae in the 2nd instar was more vulnerable than that in the 5th instar. H. indica isolate AUT 13.2 was more destructive than S. siamkayai isolate APL 12.3. The greatest mortality rate of 2nd instar larvae was 83% when H. indica AUT 13.2 was applied at the concentration of 250 IJs ml−1, and 68% when the nematode S. siamkayai APL 12.3 was used at the concentration of 300 IJs ml−1. At 250 IJsml−1, the highest mortality rate of the 5th instar larvae was 45% for H. indica AUT 13.2 and 33% for S. siamkayai APL 12.3, respectively. To customize the concentration and volume of nematodes suspension evaluated in the greenhouse settings, the most sensitive stage of FAW and the optimum concentration that caused the highest mortality were used. The concentrations of both indigenous nematodes’ isolates were 20,000 and 50,000 IJsml−1 per pot, respectively, and the results showed that the mortality rates were lower than that in the laboratory. FAW mortality rate was the highest (58%) in case of the nematode H. indica isolate AUT 13.2, against (45%) in case of S. siamkayai isolate APL 12.3, at the 50,000 IJs ml−1 concentrations. Conclusions The study revealed the 2 Thai indigenous EPNs isolates (H. indica isolate AUT 13.2 and S. siamkayai isolate APL 12.3) were capable of controlling the FAW in both laboratory and greenhouse environments. The 2 Thai EPNs showed the potential to be considered as a biological control agent.

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

“…There is an urgent need for minimizing the dependence of chemicals in pest control management. In this regard, biological control could be the promising strategy and environmentally safer than hazardous Many researchers have studied the efficacy of different nematode strains against S. frugiperda worldwide (Acharya et al 2020;Wattanachaiyingcharoen et al 2021;Fallet et al 2022), and they proved that different strains caused mortality to FAW larvae, but with different rates and concentrations.…”

“…All of these reasons contribute the EPN species to be more potency against FAW and IPM programs. Worldwide, many researchers have studied the efficacy of different nematode strains against S. frugiperda (Wattanachaiyingcharoen et al 2021;Fallet et al 2022), but till now very limited studies recorded in Egypt. Therefore, this study designed to assess the bioefficacy of 2 EPNs species (Steinernema carpocapsae (All) and Heterorhabditis indica (EGAZ2)) on different developmental FAW larval instars (2nd to 6th instars) according to different nematode concentrations and exposure times instead of chemicals.…”

Virulence of Entomopathogenic Nematodes and their Symbiotic Bacteria against Insect Pests, with Special Reference to Agrotis ipsilon (Lepidoptera: Noctuidae): A Comprehensive Review.

“…Among different EPNs, Yağcıet al (2021a) indicated that H. bacteriophora (TOK-20) isolates in Turkey were the most effective at 1000 IJs/ml concentration against last instar larvae of C. pomonella. Wattanachaiyingcharoen et al (2021) investigated the efficiencies of two Thai indigenous EPNs isolates (H. indica isolate AUT 13.2 and S. siamkayai isolate APL 12.3) against S. frugiperda and recorded the H. indica isolate as more infective than S. siamkayai isolate. Kary et al (2021) studied the effectiveness of H. bacteriophora and S. feltiae against larvae, pre-pupa, and pupa of Ph.…”