Neem as a Biopesticide

Neem oil is useful for control of aphids and prevention of aphid-transmitted diseases.

Neem oil is extracted from the neem tree (Azadirachta indica), which is native to arid regions of India. The active ingredient in neem oil is azadarachtin, which interrupts the natural lifecycle of many insects, preventing them from reaching maturity, molting and reproducing. Neem is gaining popularity because, according to the U.S. Environmental Protection Agency, it has no adverse effects to humans, wildlife or the environment.

Source

Humans have used oil extracted from parts of the neem tree for millennia for medicinal, cosmetic and pesticide purposes, according to the EPA. The tree is medium to large in size, with furrowed, dark brown to gray bark and a dense, rounded crown. The neem seeds, bark and leaves are the sources of neem extracts.

Types

Two types of neem oil are available for horticultural use and each is labeled for use on different problems. One contains the azadirachtin, the main active ingredient in the oil and the other is called clarified hydrophobic extract of neem oil, which has been treated with alcohol to remove the azadirachtin.

Function

Both types of neem oil are safe to use on food and non-food crops. Azadirachtin deters certain insects from feeding and disrupts their normal lifecycle. Clarified hydrophobic extract of neem oil performs similarly to azadirachtin, but is also labeled for use against fungal diseases.

Benefits

Neem oil is much less harmful to animal, insect and human life than commercial insecticides. It is especially effective against lepidopterons, but is also effective against whiteflies, moth larvae, mites, aphids, several types of mildew, rust and aphid-transmitted viruses.

Considerations

Neem oil works best as a preventative treatment rather than a control measure for mature adult insects. Neem oil should be applied when conditions are dry so the oil completely evaporates and plants are not at risk of phytotoxicity; dry conditions prevent damage to stressed and non-stressed plants. Neem oil will kill honeybees and contaminate water and applications should therefore be made at night or in the evening when bees are not feeding and should not be made near bodies of water.

References

• EPA: Azadirachtin (121701) Clarified Hydrophobic Extract of Neem Oil (025007) Fact Sheet
• Colorado State University Extension: Insect Control: Horticultural Oils
• Arizona Cooperative Extension: Botanical Pesticide: Neem Tree Oil and Azadirachtin
• GreeNeem: About Neem