The most efficient use of neem extracts for pest control has been found to be against chewing and sucking insects, principally lepidopterous caterpillars and beetle larvae. The active ingredient accumulates in the growing tips of the treated plants, usually reaching functional levels within 24 hours of the leaves being sprayed. No other insecticidal products have the rapidity of systemic activity of azadirachtin. Only borer type insects are not affected by this insecticide.
The relative toxicity of neem extracts to non-target organisms is low. In toxicological testing conducted by the United States Environmental Protection Agency, it was not possible to establish an 'LD-50' for azadirachtin, because no symptoms were recorded, even at the highest dosage used. As a result, there is no 'residual' or 'withholding period' necessary following the use of neem extracts.
The cost of pest control with neem extracts is relatively low. In the developing world, neem leaf or fruit (kernels) produced by farmers from their own neem trees can supply no-cost or low-cost pest control.
One problem create about degradation of this extract with light specifically degradation of azadirachtin by ultraviolet light and daylight. Some producers bypass this problem by mixing neem extract with pyrethrum derivatives; the active constituents in the mixture synergise and are long-lasting.
Another one is lots of positive sides are here for neem plant cultivation, but only one problem that neem plant grows in tropical and sub-tropical region of the world. So, climatic condition is the main factor for this plant establishment. So, it’s necessary to invent a variety which can easily in tempered regions of the world.