Environmental safety of entomopathogenic nematodes - Effects on abundance, diversity and community structure of non-target beetles in a forest ecosystem

The large pine weevil, Hylobius abietis, is a serious threat to reforestation in Europe that necessitates routine use of chemical insecticides. Application of entomopathogenic nematodes (EPN) to the coniferous tree stumps in which weevils breed has the potential to reduce the use of chemical pesticides. During field trials to assess the efficacy of nematodes against pine weevil, non-target beetles were also identified and quantified on 10 sites (14 trials). Nematodes were applied to stumps between June and July. Emergence traps captured beetles exiting from nematode-treated and untreated control stumps. Four trials were monitored in the months immediately following nematode application and ten were monitored the year after nematode application.A total of 65 species of non-target beetles were recovered, including 11 saproxylic species. We found no evidence of an effect of applied EPN on non-target beetle species richness, abundance, species richness per individual collected, or Shannon's entropy (H') either immediately or a year after nematode application, when more wood-specialists were recorded. As expected, there were marked differences between sites and/or tree species in the populations of non-target beetles recovered.These results indicate that when EPN are applied in a forest ecosystem to suppress H. abietis populations, the risk to non-target coleopteran populations must be considered negligible.

Highlights► EPN were applied to coniferous stumps to reduce populations of Hylobius abietis. ► Emergence of non-target beetles from control and EPN-treated stumps was examined. ► 4 trials were assessed in the year of nematode application and 10 in the subsequent year. ► 65 species of non-target beetles were recovered, including 11 saproxylic species. ► EPN had no effect on non-target beetle species richness, abundance or diversity.