Effects of biopesticides on demographic parameters of fall armyworm spodoptera frugiperda j.e smith (lepidoptera: noctuidae) in Morogoro Tanzania

A Dissertation 2019Fall armyworm (FAW) Spodoptera frugiperda J.E Smith is a new insect pest in Africa causing severe damage to maize (Zea mays) at its growth leading to yield loss as between 8.3 to 20.6 million metric tonnes per year (Day et al., 2017). The pest is native to America with a wide host range of about 80 plant species that makes it difficult to manage (Prasanna et al., 2018). This study aimed at establishing the population dynamics of FAW in maize treated with biopesticides. Developmental biology and demographic parameters of FAW were determined using biopesticides (Beauveria bassiana, Metarhizium anisopliae and Bacillus thuringiensis) in a commercialized maize variety (DK9089, Monsanto Company, Nairobi, Kenya). The study was conducted at the entomology laboratory of Sokoine university of Agriculture in Morogoro, Tanzania. Experiments were set in a completely randomized design (CRD) and the FAW cohorts were maintained at 26 o C and 75% relative humidity. Results on the developmental biology of FAW showed significant variations in developmental durations of immature stages of FAW among treatments. Treated cohorts had significantly longer developmental durations than untreated cohorts. Likewise, results on demographic parameters of FAW differed significantly among treatments. In life table parameters, treated cohorts had low survivorships (p < 0.001), life expectancy (p < 0.001) and high probability of dying (p < 0.001) and mortality rates (p < 0.001) than untreated cohorts. Biopesticides also showed significant variation on population parameters of FAW between treated and untreated cohorts. Treated cohorts had low net reproductive rates (p < 0.003), intrinsic rate of increase (p < 0.001), finite rate of increase (p < 0.001) and long doubling time (p < 0.001) as well as the mean generation time (p < 0.001) contrary to untreated cohorts. Results obtained from this study can be used in implementing sustainable management options against FAW populations in Tanzania and rest of the world