Virulence of four entomopathogenic nematodes against the tobacco cutworm Spodoptera litura Fabricius

Spodoptera litura Fabricius is a polyphagous pest that is seriously affecting various crops. Controlling S. litura in the fields is a challenging task due to its high resistance to most chemical pesticides. Entomopathogenic nematodes (EPNs) have been used as biological control agents against S. litura, but little information is known about their virulence. Here we compared the virulence of four EPNs, namely Heterorhabditis bacteriophora, H. indica, Steinernema carpocapsae, and S. longicaudum against each larval stage of S. litura. All EPNs caused more lethality in younger larvae than in older larvae. The mortality at all larval stages was proportional to EPN exposure time and density. The comparison among four EPNs showed that H. indica, S. carpocapsae, and S. longicaudum were associated with higher mortality, penetration rate, and reproduction rate than H. bacteriophora. These EPNs also effectively controlled S. litura in a pot assay. Our findings indicate that H. indica, S. carpocapsae, and S. longicaudum can be used as efficient biological control agents against S. litura.