Browsing by Author "Valerian, William"

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    Pathogenicity of fusarium oxysporum and effectiveness of chemical fungicides in combating cashew wilt disease in southern Tanzania
    (University of Dar es Salaam, 2020) Valerian, William
    Cashew (Anacardium occidentale L.) is an economic important cash crop in Tanzania. Despite its importance, cashew is threatened by biotic factors particular diseases. Currently, a new and serious destructive disease called Cashew Fusarium Wilt (CFWD) caused by Fusarium oxysporum has emerged. Limited information exists on appropriate management strategies against the disease, characterization and its pathogenicity. This study investigated chemical management options for the disease, characterization and pathogenicity of the causative pathogen in Lindi and Mtwara regions. The causative agent was isolated and morphologically characterized while pathogenicity tests included isolation from infected plant, inoculation to healthy plant followed by re-isolation from inoculated health seedling with similar symptoms. Three chemical fungicides: azoxystrobin, carbendazim and thiophanate methyl at different concentrations were tested under in vitro, in vivo and in situ conditions. Field and pathogenicity characterizations revealed the yellowish and brownish of leaves are CFWD symptoms caused by Fusarium oxysporum; characterized by whitish mycelia growth, chlamydospores, macroconidia and microconidia. The tested chemical fungicides significantly inhibited the mycelium growth, reduced disease severity and enhanced recovery of cashew compared to untreat under in vitro, in vivo and in situ conditions respectively (P < 0.001). Carbendazim and thiophanate methyl at all concentrations and azoxystrobin at 300 ppm, inhibited fungal growth by 100 percent. In in-vivo, carbendazim (0.2 g/L), thiophanate methyl (0.6 g/L) and azoxystrobin (0.6 g/L) effectively reduced disease severity from 11.8 to 0.9%, 11.5 to 1.3% and 11.3 to 0.2% respectively. In situ application of carbendazim at 10 g/L, azoxystrobin at 15 g/L and thiophanate methyl at 15 g/L enhanced cashew recovery from Fusarium wilt disease by 49.4, 65.2 and 21.6 percent's respectively. The study recommends the use of Carbendazim, Azoxystrobin and Thiophanate methyl in the management of CFWD in Tanzania. Further studies to establish the effect of the applied chemicals to other biota for betterment and continued applications to combat the disease are required.