The effect of extracts of neem seed on survival and infestation of thrips tabaci on onions
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Date
2003
Authors
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Publisher
Sokoine University of Agriculture
Abstract
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.
Description
Dissertation
Keywords
Research Farm, Neem seeds, Madiira Research Farm, Onion thrips management, Azadirachta indica