DEVELOPING A NEEM-BASED INSECTICIDE FOR CANADA

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Abstract
Leaves of the neem tree, Azadirachta indica A. Juss. (Meliaceae), have been used for centuries in India to protect stored grain from insect attack. Recent concern for the effects of synthetic insecticides on the environment and human health has provided the impetus for a reappraisal of the utility of neem derivatives as botanical crop protectants. Neem and its active principle, the limonoid azadirachtin, have several properties that are highly desirable for a natural insecticide. Azadirachtin is the most potent natural insect antifeedant discovered to date, suppressing insect feeding at concentrations of less than 1 part per million. Azadirachtin is also a potent insect growth regulator, which acts by disrupting molting and development, and interfering with reproduction in adult insects. These actions have been observed in over 90% of the more than 200 species of pest insects tested to date. Neem also has systemic action in some plants which could prove extremely valuable against stem- and root-feeding pests that are difficult to control. Finally, neem is essentially non-toxic to vertebrates, and in fact has a long history of medicinal use in southeast Asia.In the present paper we review our research aimed at developing a neem-based insecticide for use against pests of Canadian agriculture. We document the potent antifeedant action of azadirachtin in laboratory bioassays against the European corn borer, Ostrinia nubilalis Hübner, and the variegated cutworm, Peridroma saucia Hübner, and the molt-disrupting action of the compound in the migratory grasshopper, Melanoplus sanguinipes Fab., and the large milkweed bug, Oncopeltus fasciatus Dallas. Both antifeedant and insect growth regulatory activities of various samples of neem seed oil are shown to be correlated to azadirachtin concentrations in the oils. Field trials of an experimental neem insecticide conducted against pests of crucifers, corn, and potato in British Columbia, Ontario, and Prince Edward Island, respectively, indicate that the neem insecticide provides pest control as effective as or better than pyrethrum, the current botanical insecticide of choice for organic growers. The commercial prospectus for neem insecticides in Canada is discussed in light of our results.