Studies on natural occurrence of entomopathogenic nematodes in Vietnam

A total of 459 soil samples taken from the north to the south of Vietnam and from the coast to the high mountains were studied for the presence of Steinernema and Heterorhabditis. Using the baiting method with wax-moth larvae, 4.8%, of all samples proved to be positive for entomopathogenic nematodes, and using direct extraction of the nematodes from soil, 28% of the samples were positive. Ten Steinernema species and four Heterorhabditis species could be distinguished. based mainly oil morphological characters of the infective juveniles. Five of these species have been described front Vietnam (Steinernema tami, S. loci, S. sangi, S. thanhi and Heterorhabditis baujardi). With the exception of H. indica, all the other 'species' found could not be identified; several of the populations isolated appeared to be representatives of undescribed species. The highest diversity of entomopathogenic nematodes was found in forests, with eight Steinernema and three Heterorhabditis species.