Material name: Neem (azadirachtin, neem oil, neem oil soap)

Material Type: Botanical

U.S. EPA toxicity Category: III, “Caution” (Neemix carries a “Warning” signal word)

USDA-NOP:
Considered a non-synthetic botanical pesticide; its use is regulated. Preventive, cultural, mechanical and physical methods must be first choice for pest control, and conditions for use of a biological material must be documented in the organic system plan (NOP 2000).

Material description:
Neem products are derived from the neem tree, Azadiracta indica. The neem tree is native to southern Asia and can grow in most arid sub-tropical and tropical areas of the world (Copping 2001). Called Sarva Roga Nirvani, a “cure of all ailments” in Sanskrit, neem has been used for centuries for medical, cosmetic and pesticidal purposes. Although Indian scientists were researching the use of neem as early as the 1920s, there was little global attention until a German entomologist noticed in 1959 that neem trees in the Sudan resisted an attack of migratory locusts. Since that time, there has been considerable research and commercialization of neem products (Ruckin 1992).

Neem pesticide products are usually made by crushing neem tree seeds, then using water or a solvent such as alcohol to extract the pesticidal constituents. Other products are made from cold-pressed neem seed oil or from further processed neem oil. Neem products produced with different extraction techniques may result in different biologically active chemicals (or amounts of chemicals) being present in a product. Thus, the efficacy of different products may vary. Neem cake is the residual seed meal remaining after extraction of oil from seeds. This is often sold as a fertilizer product.

We group neem products into three classes:

Azadirachtin-based products

Includes Agroneem®, AZA-Direct®, Azatrol®, Ecosense®, Ecoside® (has both oil and azadiractin), Neemix®.

Neem oil products

Trilogy® (also packaged as Triact, Green Light Neem Concentrate, and Green Light Rose Defense) is neem oil that has had the azadirachtin and at least some other components separated from it. It is called “clarified hydrophobic extract of neem oil”. 100% cold pressed neem oil is also being sold as a “plant wash,” but has no pesticide label.

Neem oil soap products

Organica® K+ Neem is derived from neem oil that is saponified to create potassium salts of fatty acids, which are considered to be soap. It also contains 75% inert ingredients.

How it works:
Pesticide active ingredients are based on neem seed extracts, including azadirachtin, neem oil and neem oil soap. Azadirachtin, one of the more than 70 compounds produced by the neem tree, acts mainly as an insect growth regulator, but also has anti-feedant and oviposition (egg-laying) deterrent properties. First isolated in 1968, azadirachtin is thought to be the most bioactive ingredient found in the neem tree; however, such speculation may be due to it having been investigated more thoroughly then the other compounds (Thacker 2002, Quarles 1994). Most commercially available neem products list azadirachtin as the primary active ingredient. Such products are broad-spectrum insecticides, which work by contact or ingestion. As an insect growth regulator, azadirachtin prevents insects from molting by inhibiting production of ecdysone, an insect hormone. Azadirachtin is chemically similar to ecdysonlids, the hormones responsible for triggering molts (Weinzierl and Henn 1991). As an anti-feedant it may cause an insect to stop feeding after ingestion due to secondary physiological effects. As an egg-laying deterrent, volatile compounds from neem may repel some insects from depositing eggs on a plant surface.

There is evidence that other compounds found in neem have insecticidal attributes that contribute to a given product’s efficacy. A study conducted at Washington State University in conjunction with the W.R. Grace and Company (manufacturers of the neem product Margosan-O at the time) found that products containing both azadirachtin and neem oil have greater efficacy in controlling aphids than either ingredient alone (Stark and Walter 1995). They hypothesize that neem oil may help spread the chemicals on both plant and insect surfaces and allow them to penetrate into the insect more effectively. Neem seed oil is formulated and used somewhat like other horticultural oils and controls some foliar diseases as well as certain insects and mites. The oil is also made into an insecticidal soap, which probably acts similarly to other insecticidal soaps by disrupting insect membranes. (see Soap chapter).

The mechanisms for neem’s effects on mites (Miller and Uetz 1998), snails (Mostafa and Abdel-Megeed 1996), and disease organisms (EPA) have not been reported.

Active neem constituents can be absorbed through plant roots and systemically move upward through the plant through xylem tissues (Gill and Lewis 1971, Larew 1988, Nisbet, et al. 1993, Osman and Port 1990). This works best when sufficient quantities are applied to the root zone. Systemic effects are much less apparent from foliar sprays. Different plant species also differ widely in their ability to have systemic effects from neem. Neem constituents last much longer within the plant than when sprayed on the leaves. However, over time they will be diluted by growth.

Formulation and application guidelines

General Guidelines:
Neem products are generally sold as emulsifiable concentrates (EC). Neem oil soap is sold as a water-soluble liquid concentrate. While Copping (2001) reports no known incompatibilities with other crop protection agents, phytotoxicity may be a problem when combining neem oil or soap products. Read labels for specific application guidelines including determination of re-entry interval (REI) and pre-harvest interval (PHI). Range of efficacy will depend on the susceptibility of species in question and environmental conditions at time of application. However these are points to follow:

1. Make multiple applications. Frequent applications are more effective than single sprays because neem does not persist well on plant surfaces. Like most other botanically derived materials, it can be rapidly broken down by sunlight and washed away by rain (Thacker 2002).
2. Use against immature insects. Azadirachtin-based insecticides act on immature stages of insects more effectively than on eggs or adults. To reduce a build up of populations it is important to make treatments to crops targeting insects in an early stage of their life cycle. For instance, neem would likely have little effect on an infestation of striped cucumber beetle adults; however if applied to potato plants early in the season, it has been shown to greatly reduce larval activity of Colorado potato beetle.
3. Begin applications before pest levels are high. Antifeedant and egg-laying repellant effects show best results in low to moderate pest populations.
4. Neem is reported to work best under warm temperature conditions (Schmutterer 1990).
5. Neem’s systemic properties suggest that applying it to transplants just before planting to the field could be an effective and inexpensive way to control certain pests. Similarly, applying neem with relatively large amounts of water, in directed sprays over the rows of small seedlings, could be a very efficient method of application. In one study, neem applied through a drip irrigation system significantly reduced lettuce aphids on romaine by over 50% (Palumbo et al. 2001).
   

Availability and Sources:
Widely available from garden and/or farm supply mail order companies.

OMRI LISTED:
Azadirachtin-based

Agroneem (Agro Logistic Systems Inc, USA)
AZA-Direct (Gowan Company, USA)
Azatrol (PBI Gordon, USA)
Concern Garden Defense Multi-Purpose Spray (Woodstream Corp., Can.)
Ecosense (Agro Logistic Systems Inc, USA)
EcoSide (Agro Logistic Systems Inc, USA)
Neemix 0.25 Botanical Agricultural Insecticide/Insect Growth Regulator (Certis USA)
Neemix 4.5 Botanical Agricultural Insecticide/Insect Growth Regulator (Certis USA)
Safer Brand 3 in 1 Garden Spray (Woodstream Corp, Can.)

Neem Oil

Triact 70 EC (Certis, Olympic Horticultural Products, USA)
Trilogy Broad Spectrum Fungicide/Miticide (Certis USA)
Green Light Neem Concentrate (Green Light Co., USA)
Green Light Rose Defense Concentrate (Green Light Co., USA)

Neem Oil Soap

Organica® K+ Neem Insecticide - Fungicide (Organica BioTech Inc.)

References to OMRI listed products in this Guide are based on the June 2004 edition of the OMRI Brand Name List. Please consult www.omri.org for changes and updates in the brand name product listings.

NON-OMRI LISTED:

AZA 3% EC (Amvac, USA)
Amazin 3% EC (Amvac, USA): Mushrooms
Azatin 4.5WP (Certis USA)
Azatin-EC (Certis USA)
Azatin Technical (also 15%, 20%) (Certis USA)
Azatin XL (Certis USA; Olympic Horticultural Products)
BioNeem (Woodstream Corporation, USA)
Ecosin 3% EC (Amvac, USA)
Fortune Aza 3% EC (Fortune Biotech Limited, India)
Fortune Aza Technical Botanical Insecticide (Fortune Biotech Limited, India)
Margosan-O Botanical Insecticide Concentrate (Certis, USA)
Neemazal T/S1. 2% EC Insecticide (E.I.D. PARRY LTD., INDIA)
Neemazal Technical (E.I.D. PARRY LTD., INDIA)
Nimbecidine (T. Stanes & Company Ltd., India)
Ornazin 3% EC (Amvac, USA;SePro)
SuperNEEM 4.5-B Botanical Insecticide (Certis, USA)

Effects on the environment and human health
Environmental fate: Azadirachtin reportedly breaks down within 100 hours in water or light. It is relatively immobile in soil (Martineau 1994).

Wildlife: Azadirachtin is considered relatively non-toxic. Rat oral LD50 of azadirachtin is >5000 mg/kg. However, cold-water extract of fresh neem leaves caused mortality in guinea pigs and rabbits after 4 weeks of feeding trials. This extract produced reversible infertility in rats and mice after 6 weeks (Extoxnet).

Azadirachtin is not likely to accumulate or cause long-term effects (Miller and Uetz 1998). Fish toxicity is moderate and azadirachtin is not expected to kill fish under normal use.

Natural enemies: Azadirachtin has little or no negative effect on adult beneficials. It is reported to be relatively harmless to bees, spiders, ladybeetles, parasitoid wasps, and adult butterflies. The product labels advise not to apply it when honeybees are actively foraging (EPA). In a few trials, negative effects have been noted on immature stages of beneficial species exposed to neem (Qi et al. 2001, Banken and Stark 1997). However, neem products are generally thought to be suitable for inclusion into integrated pest management programs (Lowery and Isman 1994, Ruckin1992).

Other non-target organisms: Considered to be generally non-toxic. Neem leaves added to the soil increased earthworm weight and survival (Extoxnet). However, the effects of neem on many non-target organisms have not been studied, and it seems likely that some may be affected.

Effects on human health: Studies of azadirachtin mutagenicity and acute toxicity have shown that it likely does not pose a significant risk to human health. However, some people have exhibited skin and mucous membrane irritation from neem seed dust (Weinzierl and Henn 1991). Note that most studies have been done on azadirachtin, and may not show the effects of a whole neem product. Neem is used in some commercial human hygiene products.

Efficacy
Neem extracts have been shown to affect over 200 insect species including some species of whiteflies, thrips, leafminers, caterpillars, aphids, scales, beetles, true bugs and mealybugs (Thacker 2002, Copping 2001). Although neem products are labeled for many species, efficacy against them varies greatly.

Besides insects, other pests including mites (Miller and Uetz.1998, Smitley and Davis 2000) and snails (Mostafa and Abdel-Megeed 1996) have been reported susceptible to neem.
A summary of recent field neem efficacy trials on vegetables and fruit commonly grown in the Northeast was compiled for this fact sheet. These university-based trials typically test products with untreated buffer rows and other conditions that may create unusually severe pest pressure. The level of pest control is likely to be higher on completely treated fields in which good programs of cultural controls and other sound pest management tactics have been implemented.

Vegetable arthropod pests
Beetles (Coleoptera): Fair to good control has been obtained against Colorado potato beetle and Mexican bean beetle. The few published studies on flea beetles show poor to fair efficacy. Results have been mostly poor against pepper weevil.

Caterpillars (Lepidoptera): Neem gives fair control of most caterpillars. Good results have been obtained against beet armyworm, cabbage looper, and diamondback moths.

Thrips (Thysanoptera): Efficacy has mostly been poor, with one fair result against onion thrips.

Aphids (Homoptera): Generally good control, except fair against green peach aphid.

True bugs (Hemiptera): Promising results against squash bug. Fair control of stink bugs was obtained in two trials.

Other: There is one study showing fair control of potato leafhopper. Results have generally been poor against whiteflies, pepper maggots, and psyllids.

In the table below, “good control” means statistically significant reductions in pest numbers or damage of 75% or more, compared to an untreated control. "Fair control" includes those with significant reductions of 50-74%, and any non-significant reductions of over 50%. The "poor control" group includes any results with less than 50% reduction.

The products Agroneem®, Ecozin®, and Bioneem® showed little efficacy in several reported trials. With these products removed, trials are summarized in the following charts.

Azadirachtin-based neem products showed good results against beet armyworm and aphids (less so vs. green peach aphid). Less reliable but promising results were obtained against squash bug, diamondback moth, Colorado potato beetle, flea beetle, and Southern armyworm. No neem products were effective against pepper weevils, thrips, and whiteflies. Products included are Align, Amvac Aza, AZA-Direct, Azatin, Azatin XL, Fortune Aza, NeemAzal T/S, Neemix .25, and Neemix 4.5.

Fruit crops
On fruit crops, neem products have shown good results against aphids, including rosy apple aphid and wooly apple aphid; tarnished plant bug; leafhoppers, including eastern grape leafhopper and rose leafhopper; and spotted tentiform leafminer. Results have been mixed against white apple leafhopper, the apple lepidoperan complex, and mites, while those with beetles, flies, blueberry caterpillars, psyllids and scale have been poor.

Greenhouse applications
Neem has very good potential for greenhouse use. Although there have been relatively few research trials conducted, some reports indicate good to excellent results against leafminers, mealybugs, aphids, mites, flies, fungus gnats larvae, and whiteflies. Often these results have been obtained with only 1 application. There is generally a 3-7 day delay after application until maximum effect. As with most pesticides, efficacy will be improved with better spray coverage. Results have been variable according to the plant species treated, but good results have been obtained on chrysanthemum, coleus, marigold, pansy, wandering Jew, German ivy, and poinsettia. Poor control with neem in greenhouses has been noted against mealybugs on jade plant and black vine weevils on strawberries. Performance has been mixed against psyllids on tomatoes.

More research is needed in this area, but there is clearly good potential for successful use of neem products against commercial greenhouse pests.

Neem Oil Products
Neem oil is the active ingredient in the products labeled as Trilogy® (for food crops) and Triact® (greenhouse and ornamentals). They have both insecticidal and fungicidal properties. The following chart summarizes results from outdoor food-crop field trials for these products reported from 2000-2002. Best results were obtained against powdery mildew in cucurbits and grapes. The powdery mildew studies with good control all used multiple applications, from 3 to 10 times per season, while the positive gray mold study used 2 applications. The oil products were also promising against some insect and mite pests.

Neem oil soap products
We were not able to find efficacy studies on this new product. It is likely that it behaves similarly to other soaps when used for pest control.

Cost
Cost is a concern with the use of neem pesticides. At the high labeled rates most likely to give good results single full-coverage applications of neem products cost approximately $35-$100+ per acre at retail 2003 list prices. Since multiple applications are often required, cost can be high. Buying large lots directly from the manufacturer may help bring costs down.

References
Banken, J. O. and J. D. Stark. 1997. Stage and age influence on Susceptibility of Coccinella septempunctata after direct exposure to Neemix, a neem insecticide. J. Econ. Entomol. 90(5): 1102-1105.

Copping, L.G. (Eds.) 2001. The BioPesticides Manual. Second Edition. British Crop Protection Counsel.

Gill, J. S. and C. T. Lewis. 1971. Systemic action of an insect feeding deterrent. Nature (Lond.) 232:402-403.

EPA Fact Sheet. Azadirachtin (121701) Clarified Hydrophobic Extract of Neem Oil (025007). http://www.epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_025007.htm

Extoxnet. Extension Toxicology Network Pesticide Information Profiles. Azadirachtin.
Undated. http://ace.orst.edu/info/extoxnet/pips/azadirac.htm

Larew, H. G. 1988. Limited occurrence of foliar-, root-, and seed-applied neem seed extract toxin in untreated plant parts. J. Econ. Entomol. 81:593-598.

Lowery, D.T. and M.B. Isman. 1994. Effects of Neem and Azadirachtin on Aphids and their Natural Enemies. In Bioregulators for Crop Protection and Pest Control. P. A. Hedin (Eds) ACS Symposium Series 557. American Chemical Society, Washington, D.C. Ch. 7, 78-91.

Martineau, J. AgriDyne Technologies, Inc. January 26, 1994. MSDS for Azatin-EC Biological Insecticide.

Miller, F and S. Uetz. 1998. Evaluating Biorational Pesticides for Controlling Arthropod Pest and their Phytotoxic Effects on Greenhouse Crops. Hort. Technology 8(2) 185-192

Mostafa, B. and M. I. Abdel-Megeed. 1996. Molluscicidal activity of neem on Biomphalaria alexandrina. Proceedings: Sixth conference of agricultural development research 17-19 December 1996, Cairo. Annals of Agricultural Science Cairo. Special Issue, 215-232.

Nisbet, A. J., J. A. T. Woodford, R. H. C. Strang, and J. D. Connoly. 1993. Systemic antifeedant effects of azadirachtin on the peach-potato aphid Myzus persicae. Entomol. Exp. Appl. 68:87-98.

NOP. 2000. USDA National Organic Program regulations, 7CFR 205.206(e) http://www.ams.usda.gov/nop

Osman, M. Z. and G. R. Port. 1990. Systemic action of neem seed substances against Myzus persicae. Entomol. Exp. Appl. 54:297-300.

Palumbo, J. C., F. J. Reyes, C. H. Mullis, A. Amaya, L. Ledesma, and L. Carey. 2001. Neonictinoids and Azadirachtin in lettuce: comparison of application methods for control of lettuce aphids. University of Arizona 2001 Vegetable Report.

Quarles, W. 1994. Neem Tree Pesticides Product Ornamental Plants. The IPM Practitioner. 16(10) 1-13.

Ruckin, F.R., (ed). 1992. Neem, A Tree for Solving Global Problems. National Academy Press. Washington, D.C.

Schmutterer, H. 1990. Properties and potential of natural pesticides form the neem tree, Azadirachta indica. Ann. Review of Entomol. 35: 271-297
Smitley, D. R. and T. W. Davis. 2000. Twospotted spider mite on marigold in the greenhouse. Arthropod Management Tests 25: G62.

Stark, J. D. and J.F. Walter. 1995. Neem oil and neem oil components affect the efficacy of commercial neem insecticides. J. Agric. Food Chem. 43: 507-512.

Thacker, J.R.M. 2002. An Introduction to Arthropod Pest Control. Cambridge University Press.

Weinzierl, R. and T. Henn. 1991 Alternatives in Insect management: Biological and Biorational Approaches. North Central Regional Extension, Publication 401.