Entomopathogenic nematodes for the management of Agrotis ipsilon: effect of instar, nematode species and nematode production method.

Background: Previous laboratory studies have indicated the potential of some entomopathogenic nematode (EPN) species for the control of larvae of the black cutworm (BCW). To determine the most promising EPN species and the most susceptible BCW stages, a more in-depth evaluation of seven EPN species against different BCW instars was carried out, the efficacies of in vitro- and in vivo-produced EPNs were compared and the suitability of BCW instars for EPN reproduction was examined.

Results: Heterorhabditis megidis was the most virulent species, irrespective of larval stage in small arenas, followed most often by H. bacteriophora. In pots with grass, Steinernema carpocapsae tended to be the most virulent species, followed by H. bacteriophora, H. megidis and S. riobrave. Fourth and/or fifth instars were the most susceptible stages to most EPN species, and pupae the least susceptible. Furthermore, H. bacteriophora, H. megidis and S. carpocapsae successfully reproduced in fifth and sixth instars and pupae. In vivo-produced H. megidis and S. carpocapsae controlled fifth instars better than the corresponding in vitro-produced products; production method did not affect H. bacteriophora and S. riobrave efficacy.

Conclusions: Several in vitro-produced commercial EPN strains were highly virulent to BCW and warrant further testing under field conditions, along with some in vivo-produced strains.