Potential of azadirachtin-containing pesticides for integrated pest control in developing and industrialized countries

Abstract

Azadirachtin and azadirachtin-containing neem ( Azadirachta indica)-seed extracts cause various effects in insects. They act as antifeedants, growth regulators and sterilants. The effect upon insect development is most important from the viewpoint of practical insect pest control. Several hypotheses exist on the mode of action. An interference with the neuroendocrine system controlling ecdysone and juvenile hormone synthesis is suggested, but also an inhibition of ecdysone release from the hormone-producing gland ( Calliphora). In addition, azadirachtin is a chitin synthesis inhibitor. Good results in insect control are obtained with azadirachtin containing seed extracts under field conditions. Aqueous, alcoholic and enriched (azadirachtin-rich) extracts are used. The residual effect usually lasts about 4–8 days, depending on the environmental conditions and the plant species treated. Systemic effects last somewhat longer. Ultra-violet light, rainfall and perhaps high acidity on treated surfaces of plants cause a fast degradation or loss of the active material. Consequently, much higher concentrations of azadirachtin have to be used in the field to obtain results comparable to those in the laboratory. Several problems have to be overcome to develop reliable pesticides from neem-seed extracts. Inspite of the sensitivity of insects of most orders to azadirachtin, neem products are selective as they do not harm important natural enemies of pests. They are also non-toxic to warm-blooded animals. Neem-seed extracts have, therefore, a considerable potential for integrated pest control measures especially in developing but also in industrialized countries, provided certain strategies are considered for their application.