Occurrence of entomopathogenic nematodes in Osun State, Southwestern Nigeria.

In this study the occurrence of entomopathogenic nematodes (EPNs) was determined in three senatorial districts of Osun State in relation to soil texture, vegetation, moisture and pH. A total of 110 soil samples were randomly collected from various cultivated fields in different locations. The soil samples were baited twice using last instar larvae of the Galleria mellonella (greater wax moth) for presence of entomopathogenic nematodes. Four EPN isolates were recovered viz., Heterorhabditis indica, Heterorhabditis bacteriophora, Steinernema karii and Steinernema wesieri. Of a total of 110 soil samples examined, EPNs were found in 90.90% soil samples, they belonged to the genera Steinernema and Heterorhabditis. Steinernema spp. was found prevalent in both cultivated and undisturbed soils. Frequency of occurrence of EPNs in the sampled soils from the different senatorial zones was determined: soil samples from the Central zone recorded the lowest prevalence 87.50% while the soil samples from Western senatorial zone revealed 91.43% presence of the EPNs. The highest frequency of occurrence of EPNs- 94.29% was recorded in the soil samples from Eastern senatorial zone. Nematode distribution and frequency was found to be related to soil pH (pH<4.5 to pH>7.2) and soil moisture. This is the first report of these nematodes from Osun State, Nigeria. [ABSTRACT FROM AUTHOR]