Azadirachtin in neem oil

Helping Your Plants With A Neem Oil Foliar Spray

Finding safe, non-toxic pesticides for the garden that actually work can be a challenge. We all want to protect the environment, our families and our food, but most non-manmade chemicals available have limited effectiveness. Except for neem oil. Neem oil insecticide is everything a gardener could want. What is neem oil? It can safely be used on food, leaves no dangerous residue in the soil and effectively reduces or kills pests, as well as prevents powdery mildew on plants.

What is Neem Oil?

Neem oil comes from the tree Azadirachta indica, a South Asian and Indian plant common as an ornamental shade tree. It has many traditional uses outside of the insecticidal traits. For centuries, the seeds have been used in wax, oil and soap preparations. It is currently an ingredient in many organic cosmetic products too.

Neem oil can be extracted from most parts of the tree, but the seeds hold the highest concentration of the insecticidal compound. The effective compound is Azadirachin, and it is found in highest amounts in the seeds. There are numerous neem oil uses, but gardeners hail it for its anti-fungal and pesticide properties.

Neem Oil Uses in the Garden

Neem oil foliar spray has been shown to be most useful when applied to young plant growth. The oil has a half life of three 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. This makes neem oil very safe to use if applied properly.

Neem oil insecticide

Neem oil insecticide works as a systemic in many plants 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 intake it 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.

It is a useful repellent for mites and used to manage over 200 other species of chewing or sucking insects according to product information, including:

  • Aphids
  • Mealybugs
  • Scale
  • Whiteflies

Neem oil fungicide

Neem oil fungicide is useful against fungi, mildews and rusts when applied in a 1 percent solution. It is also deemed helpful for other kinds of issues such as:

  • Root rot
  • Black spot
  • Sooty mold

How to Apply Neem Oil Foliar Spray

Some plants can be killed by neem oil, especially if it is applied heavily. Before spraying a an entire plant, test a small area on the plant and wait 24 hours to check to see if the leaf has any damage. If there is no damage, then the plant should not be harmed by the neem oil.

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 over watering.

Using neem oil insecticide about once a week will help kill pests and keep fungal issues as 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?

The packaging should give information on dosage. The highest concentration currently on the market is 3%. So is neem oil safe? When used properly, it is non-toxic. Never drink the stuff and be sensible if you are pregnant or trying to get pregnant – out of all the neem oil uses, one that is currently being studied is its ability to block conception.

The EPA says the product is generally recognized as safe, so any residual amount left on food is acceptable; however, always wash your produce in clean, potable water before consumption.

There has been concern about the use of neem oil and bees. Most studies specify that if neem oil is used inappropriately, and in massive quantities, it can cause harm to small hives, but has no effect on medium to large hives. Additionally, since neem oil insecticide does not target bugs that do not chew on leaves, most beneficial insects, like butterflies and ladybugs, are considered safe.

Azadirachtin vs. Clarified Hydrophobic Extract of Neem Oil

We all want to protect our environment and fulfill our responsibilities as good stewards of the land. To that end, many gardeners seek alternatives for pest control in the landscape. Short of manually squashing every bad bug you come across, organic gardening pesticides that can cover a large area are the smart alternative. Safer® Brand has been a trusted manufacturer to generations of gardeners, and their research and development is unsurpassed in the industry for pesticide products that comply to organic standards and minimize risk to beneficial insects and the environment.

Top selling products bear ingredients like Azadirachtin and clarified hydrophobic extract of neem oil. What are these ingredients and how are they used? Both compounds stem from the amazing neem tree, a plant with numerous potentials both in the pesticide and health fields. The neem tree (Azadirachta indica) is a fast growing tree native to tropical and sub-tropical regions of the world, primarily the Indian subcontinent. Azadirachtin is extracted from the seeds of the neem tree. It is an important antifeedant, repellent, sterilizer, insect growth regulator and can also slow or cease insect egg production. It is most effective on insects in the larval stage. It acts as a stomach poison to chewing or sucking insects whose feeding behavior introduces it into their bodies.

Clarified hydrophobic extract of neem oil is a derivative product, made when neem oil is treated with alcohol, resulting in the extraction of the Azadiracthin. The remaining oil is useful on soft bodied pests like aphids and mealybugs. It is a contact insecticide, which means the product must contact the bodies of the pests to have any usefulness. The important action is suffocation. Clarified hydrophobic extract of neem oil is also effective against fungal issues such as mildews and rust.

As products derived from plants, both Azadirachtin and clarified hydrophobic extract of neem oil are non-synthetic and break down rapidly in the environment, leaving no residuals. Both products advise not to use them near water or when honeybees are actively feeding to reduce the risk of inadvertently impacting non-target insects. Neem oil and clarified hydrophobic extract of neem oil must be applied fairly frequently for best results. They are also not as effective in full sunlight since degradation increases in cases of high ultra violet light. Neither product is as fast acting or as long lasting as synthetic pesticides but combined with their non-toxic reputation and effectiveness against certain life cycles of insect pests, both neem products are well worth using in the home landscape.

A recommended insecticide and repellent is BioNeem. This product contains concentrated azadirachtin and kills and repels numerous insect pests without hurting beneficial insects. Safer® Brand has several other products containing either Azadiracthin or clarified hydrophobic extract of neem oil. These are useful on edible or ornamental plants, and in home or commercial settings.

  • The product End All® contains clarified neem oil and is pre-portioned in a spray bottle for easy use. You can even use it up to the day of harvest for fruits and vegetables.
  • Garden Defense spray concentrate is a one-gallon container that will make 128 gallons of prepared spray. It is also made from clarified hydrophobic extract of neem oil. It not only kills soft bodied insects but controls rust, black spot, mildew and other fungal diseases.
  • The 32-ounce Grub Killer Spray Concentrate is in a ready-to-use connective bottle for spraying larger areas. It contains the active ingredient Azadiracthin and targets pests at the larval stage. It is also suitable for organic gardens.

The many benefits of using neem oil products exceed their usefulness as insecticides. Ayurvedic medicine has long relied upon many parts of the plant for health and heart cures. It has even found its way into the cosmetic and beauty industries. But it is the plant’s potential as a pesticide and fungicide that will change the way the agriculture industry thinks about insecticides and plant health products. Products containing neem oil will do their job while we do ours – protecting our planet.

The above article was sponsored by Safer® Brand. The information contained in this article may contain ads or advertorial opinions.

Dodd-Frank Wall Street Reform

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AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule; technical correction.

SUMMARY:

EPA issued a final rule in the Federal Register of December 13, 1995 establishing an exemption from the requirement of a tolerance for clarified hydrophobic extract of neem oil. This document is being issued to correct the reference made to the registration number for exemption by removing it.

DATES:

This technical correction is effective July 29, 2002.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

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SUPPLEMENTARY INFORMATION:

A. Does This Action Apply to Me?

You may be affected by this action if you are an agricultural producer, food manufacturer, or pesticide manufacturer. Potentially affected categories and entities may include, but are not limited to:

Categories NAICS codes Examples of potentially affected entities
Industry 111 Crop production
112 Animal production.
311 Food manufacturing.
32532 Pesticide manufacturing.

This listing is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be affected by this action. Other types of entities not listed in the table could also be affected. The North American Industrial Classification System (NAICS) codes have been provided to assist you and others in determining whether or not this action might apply to certain entities. If you have questions regarding the applicability of this action to a particular entity, consult the person listed under FOR FURTHER INFORMATION CONTACT.

B. How Can I Get Additional Information, Including Copies of This Document and Other Related Documents?

1. Electronically. You may obtain electronic copies of this document, and certain other related documents that might be available electronically, from the EPA Internet Home Page at http://www.epa.gov/​. To access this document, on the Home Page select “Laws and Regulations,” “Regulations and Proposed Rules,” and then look up the entry for this document under the “Federal Register—Environmental Documents.” You can also go directly to the Federal Register listings at http://www.epa.gov/​fedrgstr/​. A frequently updated electronic version of 40 CFR part 180 is available at http://www.access.gpo.gov/​nara/​cfr/​cfrhtml_​180/​40cfr180_​00.html, a beta site currently under development.

2. In person. The Agency has established an official record for this action under docket control number OPP-2002-0073. The official record consists of the documents specifically referenced in this action, and other information related to this action, including any information claimed as Confidential Business Information (CBI). This official record includes the documents that are physically located in the docket, as well as the documents that are referenced in those documents. The public version of the official record does not include any information claimed as CBI. The public version of the official record, which includes printed, paper versions of any electronic comments submitted during an applicable comment period is available for inspection in the Public Information and Records Integrity Branch (PIRIB), Rm. 119, Crystal Mall #2, 1921 Jefferson Davis Hwy., Arlington, VA, from 8:30 a.m. to 4 p.m., Monday through Friday, excluding legal holidays. The PIRIB telephone number is (703) 305-5805.

II. Background

A. What Does This Technical Correction Do?

A final tolerance exemption for clarified hydrophobic extract of neem oil on various commodities was published in the Federal Register of December 13, 1995 (60 FR 63950) (FRL-4990-8). This technical correction removes the reference to the registration number in the text, considered necessary so as not to limit any other registrant. This would apply to anyone who wishes to use this chemical mixture from an alternate source in a pesticide product.

B. Why Is This Technical Correction Issued as a Final Rule?

Section 553 of the Administrative Procedures Act (APA), 5 U.S.C. 553(b)(B), provides that, when an agency for good cause finds that notice and public procedure are impracticable, unnecessary or contrary to the public interest, the agency may issue a rule without providing notice and an opportunity for public comment. EPA had determined that there is good cause for making today’s technical correction final without prior proposal and opportunity for comment, because EPA is merely removing the reference made to the registration number from the previously published final rule. EPA finds that this constitutes good cause under 5 U.S.C. 553(b)(B).

III. Regulatory Assessment Requirements

This final rule implements a technical amendment to the Code of Federal Regulations, and it does not otherwise impose or amend any requirements. As such the Office of Management and Budget (OMB) has determined that a technical correction is not a “significant regulatory action” subject to review by OMB under Executive Order 12866, entitled Regulatory Planning and Review (58 FR 51735, October 4, 1993). Because this rule has been exempted from review under Executive Order 12866 due to its lack of significance, this rule is not subject to Executive Order 13211, entitled Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, Use (66 FR 28355) May 22, 2001. This final rule does not contain any information collections subject to OMB approval under the Paperwork Reduction Act (PRA), 44 U.S.C. 3501 et seq., or impose any enforceable duty or contain any unfunded mandate as described under Title II of the Unfunded Mandates Reform Act of 1995 (UMRA) (Public Law 104-4). Nor does it require any special considerations under Executive Order 12898, entitled Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations (59 FR 7629, February 16, 1994); or OMB review or any Agency action under Executive Order 13045, entitled Protection of Children from Environmental Health Risks and Safety Risks (62 FR 19885, April 23, 1997). This action does not involve any technical standards that Start Printed Page 43552would require Agency consideration of voluntary consensus standards pursuant to section 12(d) of the National Technology Transfer and Advancement Act of 1995 (NTTAA), Public Law 104-113, section 12(d) (15 U.S.C. 272 note). Since this action does not require the issuance of a proposed rule, the requirements of the Regulatory Flexibility Act (RFA) (5 U.S.C. 601 et seq.) do not apply. In addition, the Agency has determined that this action will not have a substantial direct effect on States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government, as specified in Executive Order 13132, entitled Federalism (64 FR 43255, August 10, 1999). Executive Order 13132 requires EPA to develop an accountable process to ensure “meaningful and timely input by State and local officials in the development of regulatory policies that have federalism implications.” “Policies that have federalism implications” is defined in the Executive Order to include regulations that “substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.” This action does not alter the relationships or distribution of power and responsibilities established by Congress in the preemption provisi0ns of FFDCA section 408(n)(4). For these same reasons, the Agency has determined that this rule does not have any “tribal implications” as described in Executive Order 13175, entitled Consultation and Coordination with Indian Tribal Governments (65 FR 67249, November 6, 2000). Executive Order 13175, requires EPA to develop an accountable process to ensure “meaningful and timely input by tribal officials in the development of regulatory policies that have tribal implications.” “Policies that have tribal implications” is defined in the Executive Order to include regulations that have “substantial direct effects on one or more Indian tribes, on the relationship between the Federal government and the Indian tribes, or on the distribution of power and responsibilities between the Federal government and Indian tribes.” This rule will not have substantial direct effects on tribal governments, on the relationship between the Federal government and Indian tribes, or on the distribution of power and responsibilities between the Federal government and Indian tribes, as specified in Executive Order 13175. Thus, Executive Order 13175 does not apply to this rule.

IV. Submission to Congress and the Comptroller General?

The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the Small Business Regulatory Enforcement Fairness Act of 1996, generally provides that before a rule may take effect, the agency promulgating the rule must submit a rule report, which includes a copy of the rule, to each House of the Congress and to the Comptroller General of the United States. EPA will submit a report containing this rule and other required information to the U.S. Senate, the U.S. House of Representatives, and the Comptroller General of the United States prior to publication of this final rule in the Federal Register. This final rule is not a “major rule” as defined by 5 U. .C. 804(2).

Start List of Subjects

List of Subjects in 40 CFR Part 180

  • Environmental protection
  • Administrative practice and procedure
  • Food commodities
  • Pesticides and pests
  • Reporting and recordkeeping requirements

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Dated: June 19, 2002.

Janet L. Andersen,

Director, Biopesticides and Pollution Prevention Division, Office of Pesticide Programs.

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Therefore, 40 CFR part 180 is corrected as follows:

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PART 180—

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1. The authority citation for part 180 continues to read as follows:

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Authority: 21 U.S.C. 321(q), 346(a) and 374.

End Authority Start Amendment Part

2. Section 180.1161 is revised to read as follows:

End Amendment Part Clarified hydrophobic extract of neem oil; exemption from the requirement of a tolerance.

Clarified hydrophobic extract of neem oil is exempt from the requirement of a tolerance on all food commodities when used as a botanical fungicide/insecticide/miticide.

End Supplemental Information

BILLING CODE 6560-50-M

Plant Health November 2015

Explaining Azadirachtin and Neem
By Raymond A. Cloyd

Question: What is the difference between azadirachtin and neem?

Answer: Neem is not a single substance but is a general term for both azadirachtin and neem oil, which are derived from the neem tree, Azadirachta indica. The seed kernels contain the highest concentrations of active compounds. Seeds are soaked in water and alcohol in order to extract any pesticidal constituents. After the natural neem oil is removed from the seeds, it is treated with alcohol, which causes the azadirachtin and related substances to separate from the neem oil. The subsequent remaining oil without the azadirachtin is referred to as clarified hydrophobic extract of neem oil. The two main active ingredients derived from the neem tree seeds are azadirachtin and clarified hydrophobic extract of neem oil (also referred to simply as “neem oil”).

Azadirachtin. Azadirachtin is not a single compound. It has a very complex structure, being a mixture of related substances extracted from the neem seed kernels. The seeds are the only source of azadirachtin. Azadirachtin affects insects in many different ways including acting as an insect growth regulator, anti-feedant, repellent, sterilant and oviposition inhibitor.

As an insect growth regulator, azadirachtin acts as an antagonist by inhibiting the synthesis or metabolism of the insect molting hormone ecdysone. Consequently, by inhibiting the molting process and subsequently metamorphosis, this causes insects to die when transitioning into the next life stage or instar (insect stage between molts) thus disrupting the life cycle of insects, which prevents the production of future generations.

Azadirachtin is more effective on the immature/ young life stages of insects than eggs or adults. However, azadirachtin is slower-acting than conventional insecticides, which is primarily due to azadirachtin altering or modifying the behavior of insects. Azadirachtin works as a stomach poison in which insects must ingest the active ingredient during feeding in order to be negatively affected. Activity seems to be better on chewing than sucking insects. This may be the reason why azadirachtin is most effective against caterpillars.

Azadirachtin has minimal contact activity against most insect pests and works best at warmer temperatures (>70¡ F) with reduced efficacy at lower temperatures. Azadirachtin has been shown to have systemic properties with activity against certain insect pests, although this is contingent on plant type and pH of the growing medium, with less systemic activity at a pH greater than 7.0 (alkaline). This is interesting as azadirachtin has a low water solubility (0.05 ppm).

In addition, some studies have reported that foliar applications of azadirachtin are effective in suppressing populations of the two-spotted spider mite, Tetranychus urticae. A number of products registered for use in greenhouses that contain azadirachtin as the active ingredient include Azatin, Ornazin, AzaGuard, Molt-X, Azatrol, AzaSol and Aza- Direct. Most of these products are labeled for use against aphids, caterpillars, leafminers, mealybugs, scales, thrips and whiteflies.

Clarified hydrophobic extract of neem oil. Clarified hydrophobic extract of neem oil (neem oil) works by suffocating (blocking breathing pores) insect and mite pests. Neem oil is most active on soft-bodied insect and mite pests such as aphids, whiteflies, spider mites, mealybugs and scales.

Neem oil may kill eggs, immatures (larvae or nymphs) and adults. However, neem oil only has contact activity so it is important to obtain thorough coverage of all plant parts and make repeat applications based on label recommendations. The one product containing clarified hydrophobic extract of neem oil as the active ingredient that is registered for greenhouse use is Triact. This product is labeled for use against aphids, leafhoppers, mealybugs, mites, scales and whiteflies.

Azadirachtin and clarified hydrophobic extract of neem oil have short residual activity, primarily due to their susceptibility to ultra-violet light (sunlight) degradation, which means that repeat applications are typically required. Both compounds have low toxicity to humans and mammals with an LD50 >5,000 mg/ kg. In addition, azadirachtin and clarified hydrophobic extract of neem oil, in general, are less harmful to most natural enemies (parasitoids and predators) than conventional pesticides.

Raymond A. Cloyd

Raymond A. Cloyd is professor and extension specialist in horticultural entomology/plant protection at Kansas State University. He can be reached at

Neem Oil and Crop Protection: From Now to the Future

Introduction

Attention is increasingly being paid to the use of natural compounds (such as essential oils) as a promising option to replace agrochemicals in agricultural pest control. These odoriferous substances are extracted from various aromatic plants, which are rich sources of biologically active secondary metabolites such as alkaloids, phenolics, and terpenoids (Esmaeili and Asgari, 2015), using extraction methods employing aqueous or organic solvents, or steam distillation. Their mechanisms of action can vary, especially when the effect is due to a combination of compounds (de Oliveira, 2011; Esmaeili and Asgari, 2015).

Neem oil is extracted from the neem tree, Azadirachta indica Juss., a member of the Meliaceae family that originates from the Indian subcontinent and is now valued worldwide as an important source of phytochemicals for use in human health and pest control. Azadirachta is a fast-growing small-to-medium sized evergreen tree, with wide and spreading branches. It can tolerate high temperatures as well as poor or degraded soil. The young leaves are reddish to purple, while the mature leaves are bright green, consisting of petiole, lamina, and the base that attaches the leaf to the stem and may bear two small lateral leaf-like structures known as stipules (Norten and Pütz, 1999; Forim et al., 2014).

Neem oil contains at least 100 biologically active compounds. Among them, the major constituents are triterpenes known as limonoids, the most important being azadirachtin (Figure 1), which appears to cause 90% of the effect on most pests. The compound has a melting point of 160°C and molecular weight of 720 g/mol. Other components present include meliantriol, nimbin, nimbidin, nimbinin, nimbolides, fatty acids (oleic, stearic, and palmitic), and salannin. The main neem product is the oil extracted from the seeds by different techniques. The other parts of the neem tree contain less azadirachtin, but are also used for oil extraction (Nicoletti et al., 2012). It has been suggested that the content of azadirachtin in the seeds can be increased by artificial infection with arbuscular mycorrhiza (Venkateswarlu et al., 2008).

FIGURE 1

FIGURE 1. Chemical structure of azadirachtin, the main component of neem oil.

Among the botanical insecticides currently marketed, neem oil is one of the least toxic to humans and shows very low toxicity to beneficial organisms, so it is, therefore, very promising for the control of many pests. Target insect species include the following: Anopheles stephensi (Lucantoni et al., 2006), A. culicifacies (Chandramohan et al., 2016), Ceraeochrysa claveri (Scudeler et al., 2013, 2014; Scudeler and dos Santos, 2013), Cnaphalocrocis medinalis (Senthil Nathan et al., 2006), Diaphorina citri (Weathersbee and McKenzie, 2005), Helicoverpa armigera (Ahmad et al., 2015), Mamestra brassicae (Seljåsen and Meadow, 2006), Nilaparvata lugens Stal (Senthil-Nathan et al., 2009), Pieris brassicae (Hasan and Shafiq Ansari, 2011), and Spodoptera frugiperda (Tavares et al., 2010). Arachnid targets include Hyalomma anatolicum excavatum (Abdel-Shafy and Zayed, 2002) and Sarcoptes scabie var. cuniculi larvae (Xu et al., 2010).

The oil is considered a contact insecticide, presenting systemic and translaminar activity (Cox, 2002). It has a broad spectrum of action, inhibiting feeding, affecting hormone function in juvenile stages, reducing ecdysone, deregulating growth, altering development and reproduction, suppressing fertility, sterilizing, repelling oviposition, and disrupting molting processes (Brahmachari, 2004). Little is known about the mode of action of azadirachtin as a feeding inhibitor, although it is possible that it stimulates cells involved in feeding inhibition, causing weakness and pest death (Brahmachari, 2004).

Azadirachtin, salannin, and other limonoids present in neem oil inhibit ecdysone 20-monooxygenase, the enzyme responsible for catalyzing the final step in conversion of ecdysone to the active hormone, 20-hydroxyecdysone, which controls the insect metamorphosis process. However, these effects are probably secondary to the action of azadirachtin in blocking microtubule formation in actively dividing cells (Morgan, 2009). Moreover, azadirachtin can inhibit the release of prothoracicotropic hormone and allatotropins from the brain-corpus cardiacum complex, resulting in problems of fertility and fecundity (Mulla and Su, 1999). Meliantriol and salannin also act to inhibit the feeding of insects, while nimbin and nimbidin mainly present antiviral activity (EMBRAPA, 2008).

Azadirachtin can also interfere in mitosis, in the same way as colchicine, and has direct histopathological effects on insect gut epithelial cells, muscles, and fatty tissues, resulting in restricted movement and decreased flight activity (Wilps et al., 1992; Mordue (Luntz) and Blackwell, 1993; Qiao et al., 2014).

Several studies have described the action of neem oil in specific groups of insects. Among the major insect groups, neem oil has shown action against (i) Lepidoptera: antifeeding effect and increased larvae mortality (Mancebo et al., 2002; Michereff-Filho et al., 2008; Tavares et al., 2010); (ii) Hemiptera: early death of nymphs in due to inhibition of development and ecdysis defects (Weathersbee and McKenzie, 2005; Senthil Nathan et al., 2006; Formentini et al., 2016); (iii) Hymenoptera: food intake decrease, reduced larval and pupal development, larvae death during the molting process (Li et al., 2003); (iv) Neuroptera: severe damage in the midgut cells of larvae, injury and cell death during the replacement of midgut epithelium, and changes in cocoons, with increased porosity and decreased wall thickness affecting pupation (Scudeler et al., 2013, 2014; Scudeler and dos Santos, 2013). In another class, the Arachnida, exposure of the Ixodidae group to neem oil decreased egg hatching and caused malformation, deformities, and death of larvae and adults (Abdel-Shafy and Zayed, 2002).

Neem Applications

For centuries, neem has been used in folk medicine for the treatment of conditions such as malaria, ulcers, cardiovascular disease, and skin problems. Despite the limited existence of clinical trials to support therapeutic claims, the use of neem has expanded over time, and it is an important component of Ayurvedic medicine (medical knowledge developed in India about 7000 years ago; Girish and Shankara Bhat, 2008; Ogbuewu et al., 2011).

In addition to its medical applications, neem has aroused interest in many other areas (Figure 2). In the cosmetics and hygiene sector, neem is used in the composition of face masks, lotions, sunscreens, soaps, and toothpastes (Mathur and Kachhwaha, 2015). Products derived from neem can contribute to sustainable development and the resolution of pest control problems in agriculture (Lokanadhan et al., 2012). These products benefit from the natural properties of neem as a powerful insect growth regulator (IGR) that also affects many other organisms (such as nematodes and fungi) and can act as a plant fertilizer (Brahmachari, 2004).

FIGURE 2

FIGURE 2. Potential applications of azadirachtin in different areas.

The use of neem in agriculture is not a new practice. In India, the traditional farming system employed neem extracts for pest management and to supply nutrients to plants (Mossini and Kemmelmeier, 2005; Sujarwo et al., 2016). Scientific research has shown that neem is safe for workers, with no handling risks, and can be used throughout the entire crop production cycle (Boeke et al., 2004).

Neem has proven use as a fertilizer, with the organic and inorganic compounds present in the plant material acting to improve soil quality and enhance the quality and quantity of crops. The waste remaining after extraction of the oil from neem seeds (neem seed cake) can be used as a biofertilizer, providing the macronutrients essential for plant growth (Ramachandran et al., 2007; Lokanadhan et al., 2012).

Nitrogen is one of the main nutrients required by plants for their development, and urea is the main source of nitrogen fertilizer used worldwide to supply the nitrogen demand of crops. The control of urea hydrolysis and nitrification is one of the principal strategies employed to avoid nitrogen losses in agriculture (Ni et al., 2014). Neem has demonstrated activity as a nitrification inhibitor, helping to slow the bacterial activity that is responsible for denitrification, hence decreasing the loss of urea from the soil (Musalia et al., 2000; Mohanty et al., 2008).

Due to their compositional complexity, neem-based products can act as antifeedants, growth regulators, sterilants, anti-oviposition agents, and repellents (Gonzalez-Coloma et al., 2013). Other factors that have stimulated the use of neem-based products for pest control in agriculture are ecological and toxicological aspects (low toxicity to non-target organisms), as well as economic aspects (small amounts of the product can provide effective pest control; Ogbuewu et al., 2011).

These features of neem support its contribution to organic agricultural production systems that are more sustainable and do not generate chemical residues (plants and crops are grown without the use of any agrochemicals). This method also helps to maintain soil productivity, ensuring longer production times. Organic agriculture can be a viable alternative production method for farmers, but there are numerous challenges to be overcome. A key to success is to be open to new approaches, and in this respect neem products can effectively contribute to organic agriculture, being used as organic pesticides and as soil fertilizers. In addition, growing concerns about conventional agriculture and the demand for products that do not generate waste justify increased adoption of the use of biopesticides by farmers, which contributes to the growth of organic agriculture (Dubey et al., 2010; Seufert et al., 2012; Gahukar, 2014).

Commercial Products Derived From Neem (Azadirachta indica)

Neem has acquired commercial recognition due to its various beneficial properties, which have been extensively investigated over time. Compared to conventional chemicals, which are generally persistent in the environment and highly toxic, botanical pesticides are biodegradable and leave no harmful residues. Most botanical pesticides are non-phytotoxic and are also more selective toward the target pest. In terms of commercial applications, biopesticides can provide substantial economic advantages, since the infrastructure required is inexpensive, compared to conventional pesticides (Pant et al., 2016).

This has resulted in the publication of numerous scientific research articles and books, as well as the organization of international conferences to discuss the benefits of the plant (Girish and Shankara Bhat, 2008).

Several patents related to processes and products based on neem have been deposited in the United States, India, Japan, Australia, and elsewhere. Many of the products derived from neem are manufactured by crushing the seeds and other plant parts, followed by the use of solvents to extract the active ingredients possessing pesticide activity. The different methods and techniques employed to obtain neem products can result in different concentrations of the active compounds, as well as different biological effectiveness (Roychoudhury, 2016). Table 1 lists some of the main commercial products based on neem.

TABLE 1

TABLE 1. Neem applications and commercial products available worldwide.

Despite its many promising properties, there are limitations that hinder effective large-scale use of neem. These impediments must be overcome and many uncertainties clarified so that the full potential of neem can be exploited. One of the main problems facing the commercial development of neem is a lack of industrial interest, largely due to the difficulty of patenting natural products, as well as a shortage of scientific evidence to support claims regarding the benefits of these substances. As a results, the products are not widely publicized in the farming community and elsewhere (Pant et al., 2016).

Disadvantages of neem are its low stability under field conditions, due mainly to a high rate of photodegradation, as well as a short residence time and slow killing rates, compared to conventional pesticides (Isman, 2006; de Oliveira et al., 2014; Miresmailli and Isman, 2014). Genetic factors are mainly responsible for determining the chemical composition of neem oil. However, environmental factors and the type of extraction method can lead to significant differences in composition. As a result, there is no standard active ingredient in the composition of this botanical insecticide, which limits its application in the control of agricultural pests (Ghosh et al., 2012; Tangtrakulwanich and Reddy, 2014; Siegwart et al., 2015).

Neem oil contains a group of active ingredients with different chemical characteristics. It was therefore believed that the development of insect resistance would be virtually impossible. However, as studies have progressed, it has been observed that due to the low residual power of botanical insecticides, multiple applications are required in order to control pests, which can increase selection pressure on the pest population, possibly leading to resistance (Ghosh et al., 2012; Tangtrakulwanich and Reddy, 2014; Siegwart et al., 2015).

Currently, most of the botanical insecticides that are being studied and that are effective against many pests are those with feeding deterrent action, so their indiscriminate use could result in the development of resistance (Tangtrakulwanich and Reddy, 2014; Mpumi et al., 2016). Feng and Isman (1995) evaluated the behavior of two lines of Myzus persicae, which were exposed to pure azadirachtin or to refined neem seed extract at the same concentration as azadirachtin. It was found that after forty generations, the line treated with azadirachtin had developed ninefold greater resistance to azadirachtin, compared to a control line, whereas the line treated with the extract did not show resistance.

Future Trends

Biological control is defined as the action of natural enemies on a population of pests in order to keep it at a population density that does not cause economic damage to crops (Pal and McSpadden Gardener, 2006). Natural enemies have been known since the third century BC, when the Chinese used predatory ants for pest control in citrus. However, after 1939, with the synthesis of the chlorinated pesticide dichlorodiphenyltrichloroethane (DDT) and organophosphorus pesticides, research on synthetic chemical pesticides and their use increased greatly, while the opposite occurred with biological control methods (Doutt, 1964; Niu et al., 2014). Currently, with the emergence of the concept of Integrated Pest Management (IPM), there is a resurgence of research with emphasis on biological control techniques. Such systems seek to harmoniously integrate various forms of control, with emphasis on biological control, in order to gain economic, social, and environmental improvements (Kogan, 1998; Ehler, 2006; EPA, 2016).

The biological control of insects and mites in agriculture can be achieved using small wasps or flies, known as parasitoids, which parasitize eggs, small caterpillars, and even adults. It can also be performed using predators such as ladybugs, bugs, predatory mites, and spiders, as well as parasitism by entomopathogenic microorganisms including fungi, bacteria, and viruses (Landis et al., 2000; Ehler, 2006; Smith and Capinera, 2014). Although biological control will not control all pests all of the time, it is a key component of integrated pest management. The purpose of biological control is not to eradicate pests, but to keep them at tolerable levels at which they cause no appreciable harm (Orr and Lahiri, 2014).

There has recently been increased interest in the application of plant-based materials (botanical insecticides), such as neem oil, in pest control. Although these products are safer for the management of pests, compared to synthetic chemicals, their effects in IPM must be evaluated. Several studies have investigated the relationships between botanical insecticides and natural enemies of agricultural pests (Islam et al., 2011; Mamoon-ur-Rashid et al., 2011; Islam and Omar, 2012; Tunca et al., 2012; Usman et al., 2012). Sahayaraj et al. (2011) evaluated the use of different neem-based products in colonies of Beauveria bassiana, Isaria fumosoroseus, and Lecanicillium lecanii, and the results showed that these entomopathogenic fungi were compatible with most products tested. Raguraman and Kannan (2014) conducted a review in order to score the impact and safety of different botanical insecticides in the presence of parasitoids and predators (beneficial arthropods), with the aim of standardizing strategies and application methods to achieve better management of agricultural pests.

The integrated use of botanical insecticides associated with biological control (synergism) in IPM is becoming increasingly widespread in the farming and research communities. The advantage of this approach is that it offers the potential to control agricultural pests, without serious impacts on the environment, non-target organisms, and animal and human health.

Botanical insecticides must meet the same criteria as conventional insecticides. In other words, they must be selective for the target pest and provide sufficient residual activity to protect the plant during the period of vulnerability. Over the past decade, there has been a significant increase in the number of publications concerning the use of neem oil to control agricultural pests (Montes-Molina et al., 2008; War et al., 2012; da Costa et al., 2014; Gahukar, 2014; Rehman et al., 2014; Bakry et al., 2016). However, many studies have only involved testing at the laboratory level (in vitro), due to the instability of this substance under field conditions. From these studies, it is not possible to draw firm conclusions concerning the in vivo biological efficacy of the formulations, due to the effects of numerous environmental variables.

In order to overcome the above-mentioned limitations, nanotechnology has emerged as a novel tool to address the problems of agricultural sustainability and food security (Khot et al., 2012; Kah and Hofmann, 2014; Kookana et al., 2014; Kah, 2015; Kashyap et al., 2015; Fraceto et al., 2016). Many studies have shown that the encapsulation of agrochemicals in nanoparticulate systems can enhance the efficacy of the active ingredient, decrease toxicity toward the environment and humans, and reduce losses due to volatilization, leaching, and photobleaching (Kulkarni et al., 1999; Riyajan and Sakdapipanich, 2009; Devi and Maji, 2010; de Oliveira et al., 2014; Bakry et al., 2016; Giongo et al., 2016).

From the point of view of sustainable agriculture, nanotechnology can help in the development of environmentally friendly agricultural inputs, improving the safety and stability of active agents, enhancing their activity in pest control, and, consequently, increasing their acceptance by producers (Nair et al., 2010; Srilatha, 2011; Khot et al., 2012; Agrawal and Rathore, 2014; Ram et al., 2014). The use of nanoparticles provides an effective means of protecting neem oil against premature degradation, resulting in prolongation of its effect on the target pest. Sustained release of the active agent is achieved, and environmental damage is minimal because the polymers employed are biodegradable. Furthermore, the number of applications of neem oil can be reduced, bringing substantial economic benefits (Kulkarni et al., 1999; Isman et al., 2001; Isman, 2006; de Oliveira et al., 2014; Isman and Grieneisen, 2014; Miresmailli and Isman, 2014).

Although studies have demonstrated the beneficial effects of nanoencapsulation of neem oil, some issues need to be resolved so that the synergistic effect of nanoparticles associated with this botanical insecticide can significantly contribute to the control of insect pests. These issues include the need for: (a) regulation of the use of nanomaterials in agriculture; (b) nanoformulations that are easily scalable; (c) comparative studies employing neem formulations available commercially to prove the cost/benefit of nanoformulations; (d) detailed studies of the degradation and behavior of these nanopesticides in the environment; and (e) evaluation of toxicity toward non-target organisms (De Jong and Borm, 2008; Joint Research Centre, 2015; Servin and White, 2016).

Given the importance of neem oil and its worldwide use for combating numerous pests in different crops, the nanoencapsulation of this oil should enable the production of more stable formulations for the control of insects that damage crops, especially those that are essential for human consumption. In addition, the use of nanotechnology is an excellent way to combat the development of resistance in insects due to the indiscriminate use of neem oil.

Author Contributions

EC, JdO, and MP wrote the manuscript. LF and RdL contributed to the discussion and revised the manuscript. All authors approved the final manuscript.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Azadirachtin Vs. Neem Oil – Are Azadirachtin And Neem Oil The Same Thing

What is azadirachtin insecticide? Are azadirachtin and neem oil the same? These are two common questions for gardeners seeking organic or less toxic solutions to pest control. Let’s explore the relationship between neem oil and azadirachtin insecticide in the garden.

Are Azadirachtin and Neem Oil the Same?

Neem oil and azadirachtin aren’t the same, but the two are closely related. Both come from the neem tree, native to India but now grown in warm climates around the world. Both substances are effective for repelling and killing insect pests and also interfere with feeding, mating and egg laying.

Both are safe for humans, wildlife and the environment when used properly. Bees and other pollinators are also unharmed. However, neem oil and azadirachtin

insecticide may be slightly to moderately harmful to fish and aquatic mammals.

Neem oil is a mixture of several components, many of which have insecticidal qualities. Azadirachtin, a substance extracted from neem seeds, is the primary insecticidal compound found in neem oil.

Azadirachtin vs. Neem Oil

Azadirachtin has proven to be effective against at least 200 insect species, including common pests such as:

  • Mites
  • Aphids
  • Mealybugs
  • Japanese beetles
  • Caterpillars
  • Thrips
  • Whiteflies

Some growers prefer to alternate azadirachtin with other pesticides because doing so decreases the risk that pests will become resistant to frequently used chemical pesticides. Azadirachtin is available in sprays, cakes, water-soluble powder and as a soil drench.

When azadirachtin is extracted from neem oil, the substance left over is known as clarified hydrophobic extract of neem oil, commonly known simply as neem oil or neem oil extract.

Neem oil extract contains a lower concentration of azadirachtin, and is less effective against insects. However, unlike azadirachtin, neem oil is effective not only for insect control, but is also effective against rust, powdery mildew, sooty mold, and other fungal diseases.

Non-insecticidal neem oil is sometimes incorporated into soaps, toothpaste, cosmetics and medicine.

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