The Use of Neem Oil and Azadirachtin as Biological Insecticides

Today we talk about neem oil and azadirachtin (i.e., the active ingredient also known as azadirachtin A). To address this topic, we will begin by discussing the neem tree, from which the oil is extracted. For a long time, this active ingredient has been used in organic agriculture as an effective pesticide. Similarly, neem oil is used by home gardeners for the natural defense of plants. Many of you may wonder: aren’t these two products the same? The answer is quite complex. However, in this article, we will try to explain it in a simple yet comprehensive manner.
The difference between the active ingredient azadirachtin and products like neem oil is that, paradoxically, the former is allowed in certified organic agriculture through a complex system of ministerial authorizations.

On the other hand, the latter, despite its undisputed effectiveness as a pesticide, is not permitted as it lacks specific authorization and registration for that particular function. As you can see, the history behind this is intricate and somewhat paradoxical. So, let’s try to clarify it.

The Neem Tree

Neem oil, as the name suggests, is extracted from the neem tree, an ancient tree native to India, also known as Azadirachta indica, belonging to the Meliaceae family. It is an evergreen tree that can reach a height of up to 30 meters, with a trunk circumference of up to 2 meters. In its regions of origin, it is considered a sacred plant, often referred to as the “village pharmacy” or Arishta, meaning the “tree that cures all diseases”. Since ancient times, various parts of this tree have been used for their medicinal properties, such as antibacterial, antibiotic, and antiparasitic effects.
The neem tree was exported from India to various regions worldwide. For example, it arrived in Africa, on the edges of the Sahara, where it was used to limit desertification and provide shade to the inhabitants.
In modern times, the German entomologist Heinrich Schmutterer, in 1959, discovered the great properties of the neem tree. He was called to Sudan to help address a widespread locust invasion. When he arrived, he observed that locusts devoured the leaves of all plants except those of the neem tree. This discovery led to studies on the plant to isolate molecules with insecticidal properties.

Neem Tree Seeds

Neem oil is extracted from the seeds, which contain the highest concentration of the active ingredient. The seeds are found inside small drupe fruits. These fruits are ellipsoidal in shape, greenish-yellow in color, and about 2 cm long, resembling olives in appearance. Inside the drupe, there is a small kernel, which contains a high amount of oil (ranging from 40 to 60%). It is from this oil that the main active substances of the plant are extracted.

Azadirachtin

The active substances present in neem tree seeds are limonoids, a group of natural organic compounds. Among them, the most famous is azadirachtin A, which has been proven to have remarkable insecticidal properties. This compound is directly extracted and isolated from neem seeds to prepare commercial formulations used in organic agriculture.

Neem Oil

Cold-pressed from the seeds, neem oil is composed of various substances, including omega-6, omega-9, palmitic acid, stearic acid, and, of course, limonoids and azadirachtin. It has a pungent smell, not very pleasant, to be honest. Neem oil is readily available on the market and comes in various colors, ranging from dark yellow to brown and reddish hues.

Difference between Neem Oil and Azadirachtin

Neem oil and azadirachtin are often confused, but in practice, they are two different products. As mentioned earlier, neem oil contains this active ingredient, but the cold-pressing technique of the seeds reduces its concentration. The amount of azadirachtin present in neem oil is not higher than 0.02-0.03%. On the other hand, commercial formulations that use different extraction techniques have a concentration ranging from 1% to 2.4%, significantly higher than that found in pure oil.
Therefore, the substantial difference for agricultural use lies in the varying concentration of the active ingredient. Different manufacturers have developed and sometimes patented specific techniques for extracting azadirachtin, resulting in various commercial formulations, all with more or less high percentages of the active ingredient.

Mode of Action of Azadirachtin

Now, let’s see how azadirachtin works and why it is considered an effective biological insecticide (probably one of the oldest natural insecticides as well).
Its main action is to block the development of insects in their juvenile stages, known as juvenilizing action. Specifically, this active ingredient interferes with the hormonal system of insects, causing a chitin-inhibiting effect based on the blockage of ecdysone.
As a result, this causes alterations in the molting process of many insect species, preventing larvae or nymphs from forming their outer cuticle.
Because of this, the active ingredient of neem oil is particularly effective against young specimens at the beginning of their life cycle. However, it has not been proven to be effective against adult specimens.
Another effect of this substance is its repellent and feeding-deterrent action. In simple terms, when applied to the plant, azadirachtin significantly reduces the attraction for insects through a natural mechanism.
The action of azadirachtin occurs through ingestion and contact. Furthermore, it has a high systemic capacity on plants, meaning it remains present in the lymphatic system and exerts its effect over time (5-7 days). In some insect species, it also reduces the fertility of adult females, thus slowing down the reproductive cycle.

Why is Azadirachtin Considered a Biological Active Ingredient?

Azadirachtin is considered a natural molecule without the ability to accumulate in the environment, both in the soil, where it is decomposed by naturally present microorganisms, and in aquatic environments.
It is highly photolabile, meaning it degrades rapidly when exposed to sunlight.
Furthermore, it is non-toxic to vertebrate organisms and has low toxicity to beneficial insects such as pollinators (e.g., bees), unlike pyrethrum, which we have already come to know. Nevertheless, it is advisable to use the substance in the evening hours when these insects are not active.
The active ingredient of neem oil has varying safety intervals depending on the treated crop. The concentration of the active ingredient in the formulation also plays an important role in this. On average, the safety interval ranges from 3 to 7 days.

Which Insect Species Does the Active Ingredient of Neem Oil Affect?

Regarding vegetable crops and fruit trees, azadirachtin has proven efficacy against many insects, although, as mentioned, its effectiveness is limited to young specimens. Here is a brief list:

Black aphids;
Whitefly;
Lepidopteran larvae (e.g., noctuids, tomato leafminer, moths, leaf miners);
Thrips, such as Frankliniella occidentalis;
Coleoptera, such as the Colorado potato beetle and the swede midge;

Azadirachtin can be used effectively together with other biological remedies without losing its efficacy. For example, it can be combined with Marseille soap or Bacillus thuringiensis.
For dosages and application methods, it is always necessary to refer to the instructions on the label of the commercial formulation.

Neem Oil, Azadirachtin, and Authorization for Use in Certified Organic Agriculture

In the introduction, we mentioned that only formulations containing azadirachtin, authorized and registered by the Ministry of Health, can be used in certified organic agriculture.
The reference legislation is Regulation (EC) No. 834/2007, along with all related integrations of national laws.

An Ethical Reflection

Regarding neem oil and azadirachtin, an ethical consideration is necessary.
Commercial formulations are produced and distributed by large chemical companies in the sector, including major multinationals like Bayern or Sipcam. These products can have prohibitive costs, and the lack of ministerial authorization for pure neem oil remains somewhat unclear. It is legitimate to question why only the products marketed by these companies have access to ministerial authorization for use in certified organic agriculture. There is a strong suspicion that it might be driven by commercial speculation.
Classic neem oil, even though it contains azadirachtin and is completely natural, is not registered as an insecticide under the community directive. Therefore, it cannot be used by certified organic producers, creating a significant paradox.
The questions we raise are as follows: Is this just a matter of authorization and patents? Why is the registration of a formulation required to obtain ministerial authorization? Isn’t pure neem oil biologically sufficient?
The answers to these questions could reveal a contradiction in the system of organic certifications, which would favor the use of products marketed by large chemical companies, at the expense of non-patented natural techniques. This is because, in all probability, chemical companies, unlike small producers, have considerable financial resources, making it easier for them to support the investments required for the registration of a formulation.

Neem Oil and Azadirachtin on the Market

Neem oil has a cost to users that is, on average, about 1/5 of the cost of a registered azadirachtin-based formulation.
Many recommend the use of this oil as a natural insecticide, especially for home gardeners.
While not questioning the greater effectiveness of azadirachtin-based formulations, it seems unjustifiable to prevent the use of a natural product, milder but still effective and certainly more economical, such as neem oil, in certified organic agriculture.
Fortunately, it seems that margins for maneuver are slowly widening. Some neem oil manufacturers, despite the difficulties, have already taken steps to develop In conclusion, neem oil is a product of natural origin with a sustainable environmental impact. We hope that we have provided a comprehensive explanation of this important biological insecticide.
more accessible products for home gardeners.
Finally, we highlight a very interesting recent development concerning studies on neem oil: neem cake, which refers to the waste from neem seed processing. This can be used as an organic fertilizer, fungicide, and bio-repellent.

The Utilization of Neem Oil and Azadirachtin as Organic Insecticides

Neem oil and azadirachtin (active ingredient also known as azadirachtin A). What is the difference between these two natural insecticides?