Abstract:
Research into the insecticidal effects of azadirachtin, a limonoid from the Neem tree
(Azadirachta indica) has been ongoing for some 30 years. Its strong antifeedant, insect growth
regulatory and reproductive effects are now well understood and documented. Antiffedancy
varies markedly between species with mosquitoes being particularly sensitive to azadirachtin.
The mode of action of azadirachtin lies in (i) effects on deterrent and other chemoreceptors
resulting in antifeedancy and (ii) direct effects on most other tissues studied resulting in an
overall loss of fitness of the insect. The complexity of the molecular structure of azadirachtin has
precluded its synthesis for pesticide use although novel synthesis of the parent molecule is now
almost complete and research into simpler mimetic substances is ongoing. Applied research has
concentrated on a variety of natural formulations from neem seed kernels which contain
azadirachtin together with several structurally related molecules. This study brings the reader
up to date with both pure and applied research in the field, and provides a detailed overview of
present thinking into the mode of action of azadirachtin. Wherever possible comparative
approaches have been made between species of the effects of pure azadirachtin and areas for
future research are indicated
