The efficacy of three entomopathogenic nematodes (EPN) of family Steinernematidae was tested in different laboratory conditions in this study. The virulence of Steinernema arenarium, S. carpocapsae and S. feltiae was evaluated to fourth-instar larvae of Galleria mellonella and Tenebrio molitor. Standard temperature (25°C) and humidity (12,5 %) was used in bioassay No I. Trial No II focused on impact of temperature 10, 15 and 25°C on effectivity of S. feltiae and S. carpocapsae. Bioassay No III examined the influence of lower humidity and in consequence rehydration on virulence nematodes.

This study investigated a system comprised of entomopathogenic nematodes (EPN) (Steinernematidae and Heterorhabditidae), their symbiotic bacteria (Xenorhabdus, Photorhabdus) and an insect host, M. sexta. The focus of this investigation was to examine the effects insect host condition on the nematode-bacterium mutualistic partnership as a whole. The EPN used in the study had varying host-searching strategies: an ambusher, Steinernema carpocapsae, and a cruiser, Heterorhabditis sonorensis. Insect host age and diet were evaluated as factors that affect insect host condition. Wandering 5th instar M. sexta were much less susceptible to EPN infection compared to non-wandering 5th instar larvae, regardless of EPN species. Insect host diet had a significant impact on H. sonorensis susceptibility to EPN infection, and a non-significant trend was observed for S. carpocapsae. EPN and bacterial symbiont fitness were unaffected by insect host condition. This is the first record of the effect of insect host condition on both EPN and their symbiotic bacteria.

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