Natural Occurrence of Entomopathogenic Nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) in Spanish Soils

Entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) were surveyed in Spanish soils using the Galleria baiting technique. A total of 750 soil samples were taken from 150 sites representing different regions and habitat types (cropland, woodland, and pasture). Entomopathogenic nematodes were recovered from 35 sites; 33 sites were positive for the occurrence of steinernematids and 2 sites for heterorhabditids. Five distinct morphological types of steinernematids were recovered: Steinernema feltiae (Filipjev), Steinernema carpocapsae (Weiser), Steinernema affinis (Bovien), and two other Steinernema spp. Heterorhabditis bacteriophora Poinar was the only species of this family isolated in this survey. S. feltiae was the most common species found (23 sites). There was not a significant association between sampling time (spring/autumn) and frequency of nematode recovery. Nematodes were isolated from coastal areas (0 m elevation) to high altitude areas (2000 m). Annual median temperature and rainfall had little association with the presence of nematodes. Soil moisture and temperature regimes are more important factors in determining the prevalence of these entomopathogenic nematodes. They were associated with soils with udic moisture regimes and cryic temperature regimes. Nematodes were more frequently recovered from cropland soils than from woodland and pasture soils, but differences between habitat type were not significant.