Host potential of insects from cruciferous crops to entomopathogenic nematodes and augmentation of nematodes through oil seed rape growing

Summary

Larvae of the pollen beetles (Meligethes spp.), the brassica pod midge (Dasyneura brassicae), the cabbage seed weevil (Ceuterrhynchus assimilis), and the cabbage moth (Mamestra brassicae) were collected in the field and exposed to entomopathogenic nematodes in the laboratory. Pollen beetle larvae, seed weevil larvae and cabbage moth larvae where all relatively easy infected while infections of pod midge larvae only were observed twice. The number of nematodes produced in the cadavers was positively related to the size of the insects. The recovery of D. brassicae and Meligethes spp. was further studied after exposure to entomopathogenic nematodes during the pupating process. The recovery of D. brassicae was almost unaffected by the nematodes whereas recovery of Meligethes spp. decreased with increasing number of nematodes. The susceptibility of oil seed rape insects to entomopathogenic nematodes was indirectly demonstrated under field conditions. Here soil grown with oil seed rape for three years was compared to soil grown with grain by baiting with Tenebrio molitor. While entomopathogenic nematodes were almost absent in soil grown with grain, almost all samples were positive for nematodes in soil grown with oil seed rape.