Biocidal Efficacy of Heterorhabditis bacteriophora against the African Armyworm (Spodoptera exempta) Towards Pest Control
Biocidal Efficacy of Heterorhabditis bacteriophora against the African Armyworm (Spodoptera exempta) Towards Pest Control
Mohammed Akinlabi Rufai1*, Abideen Akinkunmi Wahab2, Kamil Ayo Fasasi1, Quadri Olusegun Adeshina1 and Mary Tolulope Awotidebe1
ABSTRACT
Studies on the biocidal activities of Heterorhabditis bacteriophora on African armyworm (Spodoptera exempta) was carried out in vivo. The H. bacteriophora was obtained from Osun state University farmland sites, Osogbo, Osun State while armyworm used in this study was obtained from the pot of a tomato plant in the botanical garden of Osun State University. Extraction of H. bacteriophora was done using decantation and centrifugation method of nematodes extraction. The five different concentrations of H. bacteriophora were made in distilled water (µg/l); one sample not treated with nematode was served as control. Biocidal efficacy was achieved by collecting soil samples, sterilized and kept into experimental plastic plates labelled as A, B, C, D, and E. This was further divided by weight into five equal portions labelled as A1-A5, B1-B5, C1-C5, D1-D5, and E1-E5, respectively. The observation was done after every twelve hours for five iterations, and the death rate was recorded. The death rates of armyworms in each soil sample after 72 hours were noticed to achieve biocidal efficacy. Maximum mortality (100%) was observed in highest concentration of nematodes (50%) after maximum time exposure (72 h); sample treated with 0% concentration had no mortality. The result shows that the death rate of the armyworm is proportional to the concentration of the H. bacteriophora and duration of application. Statistical analysis conducted using analysis of variance indicated that there was no significant difference in the overall biocidal activities of H. bacteriophora at 5% confidence limit (F>0.05). Statistical test conducted on the data also supports the reliability of the data with a correlation coefficient of 0.85<R2<1.
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