Neem spray is an vaporized mist of neem oil and is commonly used as a biological pesticide and fungicide. Neem oil is extracted from the seed kernels of the neem tree. In spray form, neem extract is used as a powerful preventative insecticide and fungicide, but in cases of severely infested plants neem spray shows little effectiveness.
Neem is derived from the neem tree Azadirachta indica, an evergreen plant native to subtropical India where it has been used for centuries. Ancient Sanskrit documents tell of the ancient uses of neem as a soil amendment and therapeutic for sick livestock. Some of the benefits of neem include treatments for skin and fungal diseases, use as an antiseptic and therapeutic, and control of insect pests. It is also used as an ingredient in cosmetics, soaps and beauty aids.
The components of the spray are natural and biodegradable, but the product should be used with caution to avoid plant injury. It is best applied to plants during the growing season, taking careful consideration to covering all parts of the plant leaves and trunk base. The spray repels over 200 various garden pests including aphids, slugs, weevils, mealybugs, caterpillars, cucumber beetles, and other chewing insects. Neem spray pesticide is highly effective at controlling larval infestations, best applied after insect eggs have hatched but before they mature to adulthood. The chemical works best in warm weather and requires multiple applications to control infestations.
The chemical compound azadirachtin in neem pesticide spray inhibits insect reproduction and larval growth by lowering levels of the growth hormone ecdysome in insects. In some cases, neem spray immediately kills insects in the nymph stage. It does not kill adult insects but does interfere with mating and reproductive processes.
Neem spray is also an effective fungicide. The spray treats powdery mildew, a common plague of damp environments and conditions. It also treats certain plant diseases carried by aphids.
Despite its many beneficial uses, neem spray can sometimes do more harm than good. Some plants, such as the black walnut, maple and juniper, may suffer since they are very sensitive to botanical oil sprays. Neem spray should never be used on stressed, drought-stricken or severely diseased plants. Sulphur compounds react with neem and should therefore be used separately at least 30 days apart.
Neem is nontoxic in most applications. The oil extract has been used for thousands of years as an antibacterial agent in soaps and cosmetics. Neem tree twigs were even used toothbrushes. Laboratory tests with rats ingesting larger quantities of neem oil and leaves interfered with rat fertility and pregnancy. Therefore, caution is urged when used near pregnant women and children.