Background: Mermithid nematodes, such as Ovomermis sinensis, display a broad host range including some lepidopteran pests. Infective juveniles penetrate their host through the cuticle, complete their growth within the hemocoel and eventually kill the host upon their emergence. Hence, mermithid nematodes are considered potential biological control agents of insect pests. Our previous data indicate that the infection rate of O. sinensis on cotton bollworm (Helicoverpa armigera) is low, which may be largely due to the strong immune system of the h...
