Neem oil (azadirachtin) as botanical pesticide

Neem oil is cold-pressed from the seeds of Azadirachta indica and contains the tetranortriterpenoid azadirachtin as its principal bioactive compound, alongside related limonoids such as salannin and nimbin. It is the most widely used botanical pesticide in Indian agriculture and is registered with CIB&RC under multiple formulations.

Composition

Active ingredient: azadirachtin (tetranortriterpenoid)
Concentration in neem seed: 0.1-0.3% by weight
Indian commercial formulations:
Neem oil 300 ppm EC (azadirachtin 0.03%)
Neem oil 1500 ppm EC (azadirachtin 0.15%)
Neem oil 10000 ppm EC (azadirachtin 1.0%)
Other constituents: salannin, nimbin, fatty acids, and aromatic oils

Mode of action

Azadirachtin acts through three concurrent mechanisms: as an antifeedant that suppresses insect feeding within hours of exposure; as an insect growth regulator that disrupts ecdysone-mediated moulting, killing larvae at the next moult; and as an oviposition deterrent that suppresses egg laying in adult females. It is broad-spectrum, with documented activity on aphids, whiteflies, jassids, thrips, mites, mealybugs, lepidopteran caterpillars and several beetle species. The compound has low mammalian toxicity and a soil half-life of 3-44 days, making it well suited to IPM and organic systems.

Target use and dose

Foliar spray: 1500 ppm EC at 2-3 ml per litre, or 10000 ppm at 0.5-1 ml per litre, repeated at 7-10 day intervals.
Soil drench: for nematode and soil-pest suppression.
IPM integration: compatible with biocontrols including Beauveria Bassiana, Metarhizium Anisopliae, Trichoderma Viride and Pseudomonas Fluorescens at most label rates.

Best activity is on early-instar larvae; mature larvae and adults often need repeated sprays. Photo-degradation is rapid, so evening application is preferred.

Safety and regulatory status

CIB&RC-registered under the Insecticides Act 1968. Low mammalian and bee toxicity at field rates. Approved for use in certified-organic production. Should not be tank-mixed with strongly alkaline products that hydrolyse azadirachtin.

References

Progress on Azadirachta indica Based Biopesticides. Frontiers in Plant Science.
Neem Oil Fact Sheet. National Pesticide Information Center.