Occurrence of entomopathogenic nematodes in Osun State, Southwestern Nigeria

Abstract

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.

Distribution of Entomopathogenic Nematodes in Some Selected Insect Species in Osogbo Local Government Area of Osun State, Nigeria

“…All farmed lands yielded zero occurrence of EPN which may be due to a myriad of anthropogenic activities bordering on land use/land cover activities. However, this observation contradicts the work of Rufai et al . (2020) who reported high occurrence of EPN in the study area.…”

“…was the major EPN species identified from the soil samples. Although, EPN species are known to occur and persist in relation to soil type and habitat, especially in sandy loam soils, which aids their mobility and survival, this current prevalence can be attributed to fewer anthropogenic activities, resulting in their spatial distribution within this site (Rufai et al ., 2020). This proved that EPN species’ disappearance from the disturbed agroecosystem results from intense anthropogenic activities over time.…”

“…Also, several surveys for EPNs have been documented with several new species and strains from Africa (Bhat et al ., 2020). However, studies on the occurrence and distribution of indigenous EPN species in Nigeria and their potential use as biocontrol agents on field trials is still at an early stage (Akyazi et al ., 2012; Rufai et al ., 2020). The use of EPNs will boost IPM in Nigeria, as well as proffering solutions in terms of cost and accessibility, especially for peasant farmers in many regions of the country dealing with high cost and difficulty in procuring pesticides, and perhaps increase food production, food security and adding positive impact on the Nigerian economy.…”