Neem oil comes from the seeds of the neem tree, Azadirachta indica, which has ancient origins in India. Organic gardeners are rediscovering the benefits of using neem oil as a way to control insects and some types of fungus. It performs its job and breaks down in the environment quickly without leaving poisonous residues. The active ingredients inhibit the larva to pupa growth stage of insects so they fail to reach adulthood. It will not harm bees, humans or other mammals.
The earliest writings on the use of neem as a protector of crops appeared about 5,000 years ago in the oldest Indian texts, known as the Vedas. Until 1933, neem cake was used as a fertilizer and insect control in fields. After 1933, the advent of modern fertilizers and insecticides discouraged the use of neem oil. The resurgence of old, tried and true, natural methods of controlling insects brings the use of neem oil to organic gardening once again.
Neem oil contains two main active ingredients. Azadirachtin controls insect growth and has a toxicity level of IV, which indicates it is nontoxic. It blocks insect hormones that trigger metamorphosis and stops maturity to the adult stage. The second ingredient, salannin, was observed in the 1960s to inhibit the feeding frenzy of desert locusts. This observation roused the interest of scientists and biologists around the world, and now neem oil is considered a very safe, nontoxic and effective regulator of insect growth and feeding habits.
Extensive testing has shown neem to be harmless to people, pets, honey bees and earthworms. It degrades rapidly in sunlight and does not leave a poisonous residue, as many modern chemicals do. Insects do not develop a resistance to neem. It is safe for the environment and actually enhances good soil ecology when neem cake, the leftovers from making neem oil, is used as a soil builder, fertilizer and food for earthworms. It is perfectly safe for human use and consumption.
Mix neem oil with water per directions on the label and use it as a spray every 4 to 5 days. Wet the tops and undersides of leaves and the soil surrounding plants. The best time to spray is in the early evening to prevent sunburn on the leaves. Spraying areas of soil where insects are in the larval and pupal stages will stop them from reaching adulthood. Neem oil will not control adult bugs.
Purchase and Storage
Purchase neem oil that is made for garden use. It contains surfactants that allow the oil to be dispersed in water. Neem oil is also available online and from garden and feed stores and farm supply stores by the pint, quart and gallon. Store in a cool, shady place. Once mixed, use within 3 days for maximum benefit.