Identification of entomopathogenic nematodes in Hainan Province, China and their efficacy against Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

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The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a notorious migratory pest native to tropical and subtropical America. It invaded China in 2018 and can reproduce annually in Hainan Province. Entomopathogenic nematodes (EPNs) have gained interest as potential bioagent due to as an alternative to conventional pesticides are EPNs. We isolated 19 EPNs out of 155 soil samples using the Galleria-baiting method. This was the first comprehensive survey of EPNs in Hainan Province. Phylogenetic analyses of the ITS and D2D3 expansion region of the 28S rDNA gene were performed, and 19 strains belonging to Steinernema aciari, Steinernema sp., Heterorhabditis sp., Oscheius sp., Oscheius myriophilus and O. amsactae were identified. It was shown that S. aciari 22,000 caused 100% and 96% mortality to the third and sixth instar larvae of S. frugiperda, respectively. When the pupae of S. frugiperda were exposed to S. aciari 22,000, the pupae died after emergence. Our study suggests S. aciari 22,000 is a promising indigenous biocontrol agent against S. frugiperda in the future. These findings underscore the importance of continued investigation into the potential of indigenous EPNs for sustainable management strategies of S. frugiperda in agricultural areas.