Browsing by Author "Rwegasira, G. M."

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    Prevalence of sweet potato virus vectors in lake victoria basin of Tanzania: a challenge to disease management techniques
    (David publishing, 2021) Rwegasira, G. M.
    : A series of experiments were conducted from 2003 to 2005 to determine the major mechanism through which sweet potato virus disease (SPVD) is spread in farmers’ fields in the Lake Victoria basin of Tanzania. Farmers’ ability to select SPVD-free vines for planting was tested followed by phytosanitary (selection and rouging infected plants) experiments conducted at six different sites in farmer fields in Bukoba and Muleba districts during short rain and long rain seasons in 2003 and 2004. In addition, the effectiveness of using SPVD-free (tissue culture developed and virus-indexed) was tested for three seasons from 2004 to 2005. It was established that farmers have skills to effectively select against SPVD-infected planting vines particularly those with apparent SPVD symptoms. SPFMV and SPCSV vectors largely contributed to new incidences of SPVD compared to the vines-based infections. SPFMV and SPCSV co-existed. The use of virus-free vines in such vector-prevalent environment was found to be fruitless efforts. It was concluded that, the use of cultivars with multiple resistance to sweet potato viruses could be the only feasible management strategies for SPVD in the Lake Victoria Basin
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    Response of spodoptera frugiperda larval instars to commonly used insecticides in Tanzania
    (Asian Plant Research Journal, 2022-12-24) Kiva, F. Mbemba; Tryphone, G. M.; Rwegasira, G. M.
    Fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a polyphagous migratory pest reported in Tanzania in 2017. Limited choices of officially registered insecticides for the control of the pest when it first occurred led to many farmers opting for the few available ones including those that were not registered for the pests. The current study drew from a survey conducted in 2018 that listed the insecticides commonly used by farmers against the pest. The study assessed the effectiveness of the insecticides against the different S. frugiperda larval instars under field conditions in the 2019 and 2020 growing seasons. Ten commonly used insecticides were applied to S. frugiperda damaged maize crops. Obtained results suggested a varied effectiveness of the tested insecticides with some inflicting significant (p < 0.001) mortality of S. frugiperda larvae while some proved ineffective. Ninja plus 5EC, Profecron 720 EC, Multi alpha plus 150 EC and Duduba 450 EC, caused highest mortality of S. frugiperda in all experimental plots accompanied with reduced incidences and damage severities on maize crops while Thunder 145 OD and Attakan 350 SC were the least effective. Yields obtained from the experiments suggested a significant impact of applied insecticides whereby plots treated with Duduba 450 EC produced the highest yield (4 tons/ha) compared to non-treated plots (2.2 tons/ha). The findings from this study prove that some insecticides were effective against the pest while some were not. As such farmers’ complaints on the ineffectiveness of traded insecticides could be real.