Neem oil is a product of the evergreen tree Azadirachta indica, and is primarily used as an organic insecticide. The most common uses for neem oil insecticide are pest control, birth control for insects and rodents, and as a fungus deterrent. Neem oil is also used in some cosmetics and hair products as well as a folk remedy to treat skin rashes such as acne.
Neem oil is extracted from the evergreen trees using either pressing or solvent extraction. The pressing process works by crushing the seeds and retaining the oil. Solvent extraction works by funneling the neem oil away from the rest of the evergreen seed particles using water and an organic solvent. As the oil is separated, it is filtered to remove impurities and the remaining oil is manufactured into neem oil insecticide.
For organic farmers, neem oil insecticide provides an appropriate level of insect and rodent control without potentially harmful chemicals being applied to food or water sources. The neem oil has been shown to be a successful deterrent against infestations of aphids, cabbage worms, Japanese beetles, mealy bug, and moth larvae. In addition, neem oil insecticide has been found safe to use for combating indoor pests such as ants, termites, mosquitoes, roaches, bedbugs, and the common housefly.
Neem oil insecticide is effective due to its unique ability to create infertility in pests and rodents. Neem oil appears to interfere with how a fertilized egg implants itself on the uterine wall. When ingested by pests or rodents during mating season or immediately following fertilization, neem oil insecticide acts as a catalyst for the body to reabsorb the fertilized egg, which terminates pregnancy. Successive applications of neem oil insecticide are required throughout the growing season for continued effectiveness.
When neem oil is applied directly to a plant's leaves, it acts as a fungus deterrent by preventing air circulation and choking off moisture. This causes the fungus to die but does not harm the growing plant. Other plant diseases thought to be controlled through the use of neem oil insecticide include black spot, rust fungus, and powdery mildew.
Though not considered harmful to mammals, pregnant women should avoid contact with neem oil, as studies have been inconclusive regarding whether the product will have the same effect on human fertilization as it does on insects and rodents. If using neem oil is required by a pregnant women, she should always wear gloves and wash her hands thoroughly after handling plants that have been treated.