Native Entomopathogenic Nematodes from Peru Control Spodoptera frugiperda, a Major Pest of Zea mays in the Peruvian Amazon

This study evaluated entomopathogenic nematodes (EPNs) isolated from a cacao agroforestry system in the Peruvian Amazon, focusing on their molecular characterization and efficacy against <i>Spodoptera frugiperda</i> (Lepidoptera: Noctuidae) larvae. Thirteen EPN isolates were obtained from 50 soil samples using the <i>Galleria mellonella</i> baiting technique. Mortality assays revealed significant differences among isolates at 24, 48, and 72 h, with isolates 11N-A4 and 8N-B1 being the most virulent, achieving maximum mortalities of 100% and 96.3% at 72 h, respectively. Median lethal time (LT₅₀) values indicated rapid action of these isolates on <i>G. mellonella</i> larvae, with 33.3 h for 11N-A4 and 32.4 h for 8N-B1. Molecular identification using ITS, D2-D3 (LSU), and COI markers confirmed the isolates as <i>Heterorhabditis</i> sp. (11N-A4) and <i>Heterorhabditis amazonensis</i> (8N-B1). In bioassays with <i>S. frugiperda</i> larvae, both EPNs exhibited dose- and time-dependent mortality. <i>H. amazonensis</i> showed rapid action, reaching 100% mortality at the highest dose (60 IJs/larvae) within 48 h, whereas <i>Heterorhabditis</i> sp. displayed a gradual, sustained increase, attaining 91% mortality at 72 h. Median lethal dose (LD₅₀) and LT₅₀ values reflected the efficiency of both isolates, with <i>Heterorhabditis</i> sp. achieving lower LD₅₀ at later stages and shorter LT₅₀ at low-to-intermediate doses. These findings highlight the potential of <i>Heterorhabditis</i> sp. and <i>H. amazonensis</i> as effective biocontrol agents adapted to local conditions and represent the first report of <i>H. amazonensis</i> in Peru. Further studies under field conditions are required to confirm their suitability for incorporation into integrated pest management strategies in the Peruvian Amazon.