Virulence of Philippine entomopathogenic nematode isolates against strains of fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae)

The control of fall armyworm (FAW), Spodoptera frugiperda, has been a significant concern to corn and rice agroecosystems in the Philippines. As one of the strategies for FAW management, recent studies have focused on developing entomopathogen-based control tactics, of which utilization of entomopathogenic nematodes is considered as a promising option. This paper evaluated the efficacy of the Philippine isolates of Heterorhabditis indica (HiBSDS, HiMAP, HiPBCB) and Steinernema abbasi (SaMBLB) against the two strains of S. frugiperda. Results showed that all isolates are virulent to both strains 24-48 h post-infection (hpi). However, to achieve similar FAW mortality, H. indica was found to require less IJ measured through penetration percentage as compared with S. abbasi. Lower LC50 and LT50 values were also observed for H. indica isolates than SaMBLB. Among the H. indica isolates, no intraspecific variability in terms of virulence was observed. More apparent is the interspecific variability between S. abbasi and H. indica, as the latter demonstrated higher virulence activity. The FAW strains also showed similar level of sensitivity relative to each of the EPN treatments. Although this warrants further greenhouse and field efficacy study, the findings demonstrated the biocontrol potential of these local EPN isolates against FAW which can also be incorporated in integrated pest management of this insect pest in the Philippines.