Occurrence and diversity of the entomopathogenic nematode Oscheius myriophilus (Nematoda: Rhabditida) in the Italian outbreak area of Popillia japonica (Coleoptera: Scarabaeidae)

The genus Oscheius includes species with different habits and some of them have been shown to kill some insect pests. The occurrence of Oscheius in hay meadow soils from the recently invaded area by the Japanese beetle Popillia japonica in Lombardy, Italy has been surveyed. Oscheius myriophilus was detected at 5 out of 18 sites resulted positive to EPN, either alone or together with other genera of EPN, indicating a widespread occurrence. The morphological analysis of the strains retrieved showed that they are morphologically in agreement with those of the type population and with other populations recently described. The phylogenetic analysis supported the sub-grouping of all sequences of O. myriophilus from Lombardy with those present in the databases and a close relationship with O. safricana was observed. The capacity to kill the laboratory host Galleria mellonella was similar to that observed in a previous study related to isolates from P. japonica, although O. myriophilus did not cause significant mortality in laboratory trials with the invasive beetles. The isolates of O. myriophilus from Lombardy were characterized in relation to their infectivity to G. mellonella and the response to environmental stress, such as heat tolerance and desiccation. Overall, O. myriophilus appears to be an important component of the EPN community of hay meadow soil in Lombardy and might play a role in the containment