Helping Your Plants With A Neem Oil Foliar Spray

Neem oil is also a useful repellent for mites and is used to manage over 200 other species of chewing or sucking insects according to product data. It helps manage populations of a variety of pests, including:

Neem Oil Fact Sheet

Neem oil is a naturally occurring pesticide found in seeds from the neem tree. It is yellow to brown, has a bitter taste, and a garlic/sulfur smell. It has been used for hundreds of years to control pests and diseases. Components of neem oil can be found in many products today. These include toothpaste, cosmetics, soaps, and pet shampoos. Neem oil is a mixture of components. Azadirachtin is the most active component for repelling and killing pests and can be extracted from neem oil. The portion left over is called clarified hydrophobic neem oil.

What are some products that contain neem oil?

Neem oil and some of its purified components are used in over 100 pesticide products. They are applied to a wide variety of crops and ornamental plants for insect control. Neem oil can be formulated into granules, dust, wettable powders or emulsifiable concentrates. Always follow label instructions and take steps to avoid exposure. If any exposures occur, be sure to follow the First Aid instructions on the product label carefully. For additional treatment advice, contact the Poison Control Center at 1-800-222-1222. If you wish to discuss a pesticide problem, please call 1-800-858-7378.

How does neem oil work?

Neem oil is made of many components. Azadirachtin is the most active. It reduces insect feeding and acts as a repellent. It also interferes with insect hormone systems, making it harder for insects to grow and lay eggs. Azadirachtin can also repel and reduce the feeding of nematodes. Other components of neem oil kill insects by hindering their ability to feed. However, the exact role of every component is not known.

How might I be exposed to neem oil?

People can be exposed to chemicals by eating them, breathing them in, through skin contact and eye contact. Since neem oil is used on a variety of crops, people are mainly exposed to neem oil in their diet. People who apply neem oil may also be exposed if they inhale the mist or dust, let the product touch their skin, or fail to wash their hands before eating or smoking. However, the label includes directions for keeping exposure low. For example the label might require applicators to wear protective clothing.

What are some signs and symptoms from a brief exposure to neem oil?

Neem oil can be slightly irritating to the eyes and skin. Azadirachtin, a component of neem oil, can be very irritating to the skin and stomach. The remaining portion of neem oil is made of fatty acids, essential oils and other substances that are commonly eaten in a normal diet. These substances are generally recognized as safe (GRAS) by the United States Food and Drug Administration. In other countries, neem oil has been used on cats for flea control. Some adverse reactions have been reported. Symptoms include feeling sluggish, excessive salivation, impaired movement, trembling, twitching, and convulsions. Some of the cats died. However, most of them recovered within 1 to 5 days.

What happens to neem oil when it enters the body?

Clarified hydrophobic neem oil (without azadirachtin) is made of fatty acids and glycerides. These substances are commonly found in food. When they enter the body, they are broken down, used for energy, and incorporated into cells. In one study, scientists injected insects with azadirachtin. They found 90% of the dose in the insects’ feces within 7 hours. The remaining portion lingered in the insects’ bodies for 24 days after the injection.

Is neem oil likely to contribute to the development of cancer?

No. People have been exposed to neem oil in many ways for hundreds of years. During this time no association with increased cancer risk has been found. Studies showed that neem oil did not alter or damage genes. In laboratory tests, animals were fed neem oil for 90 days. They did not have increased cancer rates. Further, one study found that certain components of neem oil caused cancer cells in hamsters to stop growing or die. Another study looked at prostate cancer cells from humans. Researchers found that neem leaf extract was able to slow their growth.

Has anyone studied non-cancer effects from long-term exposure to neem oil?

In rat studies, no effects were reported when the rats were fed either azadirachtin or clarified hydrophobic neem oil throughout their lives.

Are children more sensitive to neem oil than adults?

In general, children may be especially sensitive to pesticides compared to adults. When rats were fed neem oil in one study, their pregnancies ended. In another study, rats were fed azadirachtin in their diet throughout their lives. No effects to their offspring were found. Additionally, neem oil is used in toothpaste, cosmetics, soaps and traditional medicines around the world. Therefore, people of all ages are commonly exposed to neem oil. No data were found to show that children are more sensitive than adults to neem oil.

What happens to neem oil in the environment?

Azadirachtin, a major component of neem oil, is rapidly broken down. Microbes and light break down the pesticide in soil, water and on plants. The half-life of azadirachtin in soil ranges from 3-44 days. In water, the half-life ranges from 48 minutes to 4 days. It also rapidly breaks down on plant leaves; the half-life is 1-2.5 days. The remaining components of neem oil are broken down by microbes in most soil and water environments.

Can neem oil affect birds, fish, or other wildlife?

Neem oil is practically non-toxic to birds, mammals, bees and plants. Neem oil is slightly toxic to fish and other aquatic organisms. Azadirachtin, a component of neem oil, is moderately toxic to fish and other aquatic animals. It is important to remember that insects must eat the treated plant to be killed. Therefore, bees and other pollinators are not likely to be harmed.

Where can I get more information?

For more detailed information about neem oil please visit the list of referenced resources below or call NPIC, Monday – Friday, between 8:00am – 12:00pm Pacific Time (11:00am – 3:00pm Eastern Time) at 800-858-7378.

Please cite as: Bond, C.; Buhl, K.; Stone, D. 2012. Neem Oil General Fact Sheet; National Pesticide Information Center, Oregon State University Extension Services. http://npic.orst.edu/factsheets/neemgen.html.

References:

1. Pesticide Product Information System; U.S. Environmental Protection Agency, U.S. Government Printing Office: Washington, DC, 2012.
2. Neem Oil; Tolerance Exemptions. Fed. Regist. December 13, 1995, 60 (239), 63950-63953.
3. Azadirachtin Summary Document Registration Review; EPA-HQ-OPP-2008-0632-0002; U.S. Environmental Protection Agency, Office of Pesticide Programs, Biopesticides and Pollution Prevention Division, U.S. Government Printing Office: Washington, DC, 2008.
4. Biopesticides Registration Action Document (BRAD) Cold Pressed Neem Oil; EPA-HQ-OPP-2007-0996-0002; U.S. Environmental Protection Agency, Office of Pesticide Programs, Biopesticides and Pollution Prevention Division, U.S. Government Printing Office: Washington, DC, 2009.
5. Cold Pressed Neem Oil; Exemption from the Requirement of a Tolerance. Fed. Regist. October 28, 2009, 74 (207), 55458-55463.
6. Krieger, R. I. Handbook of pesticide toxicology, 2nd ed.; Academic Press: San Diego, 2001; pp 130-134.
7. National Research Council. Neem : a tree for solving global problems; National Research Council; National Academy Press: Washington, DC, 1992; p 141
8. Reigart, J. R., Roberts, J. R. Recognition and Management of Pesticide Poisonings, 5th ed.; U.S. Environmental Protection Agency; Office of Prevention, Pesticides, and Toxic Substances, U.S. Government Printing Office: Washington, DC, 1999; p 63
9. Schmutterer, H. The neem tree : Sources of unique natural products for integrated pest management, medicine, industry, and other purposes; VCH Publishers, Inc.: New York, 1995.
10. Sutton, N. M.; Bates, N.; Campbell, A. Apparent adverse reactions to neem (margosa) oil in cats. Vet. Rec. 2009, 164 (19), 592-593.
11. Harish Kumar, G.; Vidya Priyadarsini, R.; Vinothini, G.; Vidjaya Letchoumy, P.; Nagini, S. The neem limonoids azadirachtin and nimbolide inhibit cell proliferation and induce apoptosis in an animal model of oral oncogenesis. Invest. New Drugs 2010, 28 (4), 392-401.
12. Kumar, S.; Suresh, P. K.; Vijayababu, M. R.; Arunkumar, A.; Arunakaran, J. Anticancer effects of ethanolic neem leaf extract on prostate cancer cell line (PC-3). J. Ethnopharmacol. 2006, 105, 246-250.
13. Srivastava, M. K.; Raizada, R. B., Lack of toxic effect of technical azadirachtin during postnatal development of rats. Food Chem. Toxicol. 2007, 45 (3), 465-71.

NPIC fact sheets are designed to answer questions that are commonly asked by the general public about pesticides that are regulated by the U.S. Environmental Protection Agency (U.S. EPA). This document is intended to be educational in nature and helpful to consumers for making decisions about pesticide use.

Related NPIC Topics:

Helping Your Plants With A Neem Oil Foliar Spray

Pests and fungal infections can be real problems in the garden despite your best efforts. There are plenty of chemical pesticides and fungicides on the market, but for something natural and safer, try neem oil. We all want to protect the environment, our families, and our food, but many natural chemicals have limited effectiveness. Neem oil insecticide is an exception. Neem oil can safely be used on food, it leaves no dangerous residue in the soil, and effectively reduces or kills pests.

What Is Neem Oil?

A natural pesticide with some fungicidal properties, neem oil is made from the seeds of the neem tree (Azadirachta indica). The primary active insecticidal ingredient in neem oil is azadirachtin. The neem tree is native to South Asia, where it has been used as an insecticide and in soaps, waxes, cosmetics and oils for hundreds of years.

It deters insects from feeding on plants and regulates growth. Rather than killing pests, neem oil stops them from eating and growing. For this reason, it is most effective when targeting insects in their immature stages.

Neem Oil Benefits

Of the many products on the market for managing pests and fungal infections, neem oil has some exceptional benefits. The primary benefit is that it’s non-toxic and natural. While harmful to certain insects, its toxicity in mammals is low. It does not produce a toxic buildup in the environment and is safe for most plants when used as directed. You can use neem oil safely on vegetables.

Neem oil is also a useful repellent for mites and is used to manage over 200 other species of chewing or sucking insects according to product data. It helps manage populations of a variety of pests, including:

• Aphids
• Thrips
• Whiteflies
• Mealybugs
• Spider mites
• Caterpillars
• Nematodes
• Scale
• Whiteflies

Uses of neem oil also include battling fungal infections, but it is less effective for this purpose. It is most often used to manage powdery mildew on plants, but once any fungal infection has set in, controlling it is challenging.

Neem Oil as an Insecticide

As an insecticide, neem oil is pretty effective. It works best when the insects are in immature stages. A coating of oil on foliage can suffocate insects, killing them, but neem mostly works as the plant absorbs and metabolizes it. When insects feed on the plant that has absorbed neem oil, they stop eating. It also interferes with insect hormones, stopping growth, egg laying, and other life cycle behaviors. While neem can be effective against pests, it is not a quick fix. It may take several applications to see results.

Neem Oil as a Fungicide

Neem oil can be used as a fungicide as well, but its effectiveness is limited. It may help control infections from fungus, mildews and rust by preventing spores from germinating and penetrating plant tissue. It will not cure a plant that is already infected with a fungus, but it can help slow or prevent the spread of infection to healthy tissue. It works best on powdery mildew. It is also deemed helpful for other issues such as:

• Root rot
• Black spot
• Sooty mold

How to Use Neem Oil on Plants

Neem oil foliar spray has been shown to be most useful when applied to young plant growth. The oil has a half-life of 3 to 22 days in soil, but only 45 minutes to four days in water. It is nearly non-toxic to birds, fish, bees, and wildlife, and studies have shown no cancer or other disease-causing results from its use. Apply neem oil at a time of day when bees aren’t typically out foraging for pollen, such as night time or early in the morning. Insects would have to eat the treated plant, so neem oil is very safe to use if it’s applied properly.

You can find neem oil spray in most garden centers, either in a concentrated form that must be diluted with water or as a ready-to-spray product. Thoroughly cover leaves, including their undersides and stems. Because the plant absorbs the neem oil, you don’t have to worry about rain washing it away.

While neem oil is largely safe, some plants might be sensitive to it. Before covering a plant entirely in neem oil, test a small area and see if it causes damage. To reduce the risk of damage, avoid using neem oil in bright sunlight or when it is very hot. It’s better to apply it in the evening to give the plant time to absorb it. Don’t use it on plants you have just transplanted or are under stress.

How Does Neem Oil Work?

In many plants, neem oil insecticide works as a systemic when applied as a soil drench. This means it is absorbed by the plant and distributed throughout the tissue. Once the product is in the plant’s vascular system, insects take it in during feeding. The compound causes insects to reduce or cease feeding, can prevent larvae from maturing, reduces or interrupts mating behavior, and, in some cases, the oil coats the breathing holes of insects and kills them.

Apply neem oil only in indirect light or in the evening to avoid foliage burning and to allow the treatment to seep into the plant. Also, do not use neem oil in extreme temperatures, either too hot or too cold. Avoid application to plants that are stressed due to drought or overwatering.

Using neem oil insecticide about once a week will help kill pests and keep fungal issues at bay. Apply as you would other oil-based sprays, making sure the leaves are completely coated, especially where the pest or fungal problem is the worst.

Is Neem Oil Safe for Dogs and People?

Neem oil is generally safe for people, pets, and most wildlife. Because pollinators and other beneficial insects do not chew plants, they should not be affected by neem on plants. Neem oil does not stay long in the environment, so its impact is minimal.

Although considered safe, you should still take precautions when using neem oil. Spray neem oil on plants only as directed and wear gloves. It can potentially irritate your eyes or skin. Children may be more sensitive to azadirachtin. Anyone pregnant or trying to become pregnant should avoid neem oil entirely. The EPA deems neem oil to be generally recognized as safe, but you should always wash your produce in clean, potable water before consumption.

As with any pesticide, use neem oil as a last resort. Prevention is always best. Use healthy plants and practice good garden management to minimize pest issues and fungal infections.