Browsing by Author "Haule, John Bosco"

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    The effect of extracts of neem seed on survival and infestation of thrips tabaci on onions
    (Sokoine University of Agriculture, 2003) Haule, John Bosco
    Field and laboratory studies were conducted at Madiira Research Farm, Arusha to investigate the effectiveness of extracts of neem seeds for management of onion thrips, Thrips tabaci on onions. The efficacy and performance of extracts from N eem seeds, Azadirachta indica was compared with that of Fenitrothion, a commonly used standard insecticide. Neem extracts at concentrations of 0.8% and 1.0% AZ gave good protection against T. tabaci under field condition. A significant decline in population density (P = 0.05) o f o nion t hrips w as o bserved a mong t reatments. F ewer t hrips 1 arvae a nd adults were recorded on treated plants than on control. However, the effectiveness and performance of extracts of neem seed varied with concentration and method of application. Alcohol extracts (0.8%) and aqueous extracts (1.0%) were more effective in lowering the number of T. tabaci. These levels of concentration compared favourably with fenitrothion. Significant differences (P=0.05) in onion yields were generally observed among treatments. Onions treated with extracts of neem seed gave higher yield than the control. The yields were not significantly different from fenitrothion treated crop. Neem seed extracts, even at the low concentration of 0.4 and 0.5%, resulted into significant mortality and ovipositional deterrence of thrips, but were less effective as repellents. Mortality and repellence increased with time and concentrations. At concentrations of 0.4 and 0.5% more thrips were found dead and strayed off from treated leaves. No mortality and repellence occurred in the control leaves. Onion leaves treated with the standard insecticide, fenitrothion, resulted to high death and repellence of thrips at 24 and 48 hours post treatment. The use of neem extracts proved to be effective in providing good protection of onions against T. tabaci. Neem seed extracts have shown good potential for management of onion thrips on onions due to low cost, effectiveness, safety, availability and their easiness to prepare and use.