Pathogenicity of native isolates of entomopathogenic nematodes (Heterorhabditis and Steinernema) against Spodoptera frugiperda under arid coastal conditions

Abstract

Given the increasing resistance of Spodoptera frugiperda to chemical insecticides, entomopathogenic nematodes (EPNs) offer a sustainable alternative. This study aimed to isolate and identify native EPNs from agricultural soils in Lambayeque, Peru, evaluate their spatial distribution, and determine their pathogenicity against S. frugiperda under arid coastal conditions. Out of 267 soil samples collected from various agroecosystems, 7.5% tested positive for EPNs, revealing a global distribution (R-index = 0.453) in perennial crops. Molecular analysis (ITS) confirmed identities with over 99.4% similarity to Heterorhabditis indica and Steinernema diaprepesi, representing the first genetic report of the latter in Peru. In vitro bioassays against S. frugiperda showed that Heterorhabditidae strains caused mortality rates > 85% (at 80 IJs/larva); specifically, strain UNPRG.SV 01 exhibited the lowest median lethal concentration (LC50 = 4.63 IJs/larva), followed by UNPRG.SV 10 (LC50 = 8.02). Conversely, while UNPRG.SV 19 (Steinernematidae) showed less than 15% lethality in vitro, in vivo trials demonstrated 70.0% efficacy over 96 h, which was statistically comparable to chemical insecticide performance (72.5%). These results indicate promising biocontrol potential of these native isolates and their potential integration into integrated pest management programs.