Neem oil on plants: tips for using neem oil in the garden

Neem oil on plants: tips for using neem oil in the garden

Plant protection products based on neem oil can be used for natural pest control of aphids, spider mites and other plant pests. You can find out how to use neem oil to protect your plants here.

Neem oil can be used in many ways. Its use as a plant protection agent shows great potential. In the following text, we give you exciting background information and explain how you can use neem oil in your garden or at home.

Neem tree: origin & characteristics

The neem tree (Azadirachta indica) belongs to the mahogany family (Meliaceae) and therein to the genus Azadirachta. This tree is also sometimes referred to as Indian lilac or nimtree. From this, you could deduce that the neem tree originated in South East Asia. More precisely, the neem tree commonly grows in India, Myanmar, Bangladesh and Pakistan. Because the neem oil extracted from the tree’s seeds is so popular and because it grows in most arid subtropical and tropical areas, the tree is now also cultivated in Australia, America and Africa.

The neem tree can reach a height of 20 metres and an astonishing age of up to 200 years. Additionally, it is very drought tolerant. It grows rapidly and can bear fruit after only a few years. A fully-grown tree can produce up to 50 kg of fruit.

The flowers are white, and their scent is reminiscent of jasmine. The resulting edible fruits are oval in shape and up to 2.5 cm long. The seeds they consist of up to 40% oil and that is where neem oil comes from. The helpful active ingredients of the neem tree are found in all parts of the plant, but in different compositions.

Almost all parts of the neem tree are used in different ways: leaves, seeds, flowers and even the bark. For example, during the Indian New Year, Hindu believers bathe in an extract made from the leaves of the neem tree. This supposedly cleanses not just the body but also the soul. Interestingly, the branches of the neem tree were formerly used to clean teeth.

Neem oil: production of the plant protection product

The fruits that fall from the neem trees are collected and the pulp is removed. What remains are the seeds, which are processed in a variety of ways. Neem oil is can be produced using these three methods:

  • Cold pressing: The whole or ground seeds of the nimtree are gently pressed. This produces a yellow and bitter-smelling oil.
  • Water extract: Another method to produce neem oil is water extraction. Unfortunately, it is not as effective, but it is cheaper than the other methods. The ground kernels are soaked in water and an extract is thus obtained.
  • Oil extraction: Neem oil can also be extracted from the kernels. Saturated hydrocarbon (hexane) is used for this.

Many insecticidal and acaricidal substances are found in the neem tree. The former is effective against insects, the latter against arachnids such as mites.

  • Azadirachtin (the main active substance)
  • Nimbin
  • Nimbidin
  • Nimbandiol
  • Salannin
  • Meloiantriol
dried neem fruits
Neem oil can be extracted from the fruits []

With an optimal extraction of the oil from the seeds, an azadirachtin content of 30% can be obtained in the oil.

Tip: If you have purchased neem oil prepared in this way, you should store it in a cool and dark place so that it does not go bad and does not lose its effectiveness.

Neem for pest control

The active ingredients from the oil of the neem tree give us an excellent opportunity to control pests on plants in a natural way.

Neem oil can be used against these pests

Plant protection products containing neem are mainly used against insects that damage useful or ornamental plants with their biting or sucking. It is particularly effective against biting insects, as it is absorbed by the insects while they feed. The azadirachtin in neem oil has an inhibiting effect on feeding and disturbs the moulting (or ecdysis) of the insects. Neem has a wide spectrum of application and can be used against the following insects:

  • Beetles (Coleoptera) like the potato beetle (Leptinotarsa decemlineata) or weevils (Curculionidae).
  • Coleoptera (Homoptera), which includes aphids (Aphidoidea) or cicadas (Auchenorrhyncha).
  • Diptera, or simply different species of flies.
  • Butterflies and moths of the Lepidoptera order, which include pests such as the box tree moth (Cydalima perspectalis).

How to use neem oil against plant pests

Primarily, azadirachtin from neem oil is effective against the larval stages by reducing production of the hormone ecdysone, which is important for the moulting of the larvae. This disrupts or delays the larval metamorphosis and prevents adult insects from developing from the larvae. The insects either die, are damaged or can no longer reproduce. In adult insects, neem inhibits the feeding activity. Death is not immediate, but the feeding stop occurs relatively quickly. As these hormones are very widespread in the insect kingdom, azadirachtin and neem are not specific, but have a broad effect. It should also be noted that azadirachtin only affects the last larval stages and some degree of damage by larvae cannot be avoided completely.

The following effects of neem oil can be observed in insects:

  • Feeding inhibitor
  • Feeding deterrent
  • Moulting and pupation disorders
  • Disturbance during egg laying
  • Reduced reproductive capacity

As the active ingredients of neem oil are absorbed by the plants, insects that do not come into direct contact with the agent but eat the plant or mine through leaves or roots can also be detected. Mining means that an insect eats inside a leaf and thus creates tunnels or mines. The absorption of the active ingredient into the plant is sub-systemic, so it is not distributed throughout the plant, but only in the immediate vicinity of the sprayed parts of the plant.

Tip: Preparations based on neem oil are particularly effective against aphids or whiteflies.

Neem oil pest control & plant protection

Important: The use of specially mixed preparations of neem oil as plant protection agents is not permitted. In the EU, only products that have been tested and approved are allowed for use. Illegal use could result in substantial fines. The same applies to the use of vinegar, rapeseed oil or soft soap on plants. If you want to use the oil of the neem tree, we recommend an approved product based on neem oil.

Neem can also be used as a powder, which is just as easy to buy as neem oil. Residues from oil production – the neem cake – can be dried and processed into powder or pellets. These products can be worked into the soil to improve it. Moreover, neem cake can be used as a fertiliser and can even combat nematodes that dwell underground and damage plants.

neem powder in a bowl
Neem can also be used as a powder [ THOMAS A]

The by-product of neem oil production, the neem cake, can be used in other ways, too. The neem cake consists of the whole seeds of the neem tree, which are crushed.

This precious oil has many advantages, but like any remedy, neem oil has side effects. Some plants are sensitive to the product and lose their leaves through phytotoxic reactions. All in all, processed and diluted neem preparations are better tolerated by plants than pure neem oil.

Although it is amazing just how versatile neem is in plant protection, neem oil cannot distinguish between pests and useful species and, unfortunately, can just as easily harm beneficial insects. Beneficial insects, such as parasitoid wasps Aphidius rhopalosiphi, lacewings (Chrysoperla carnea) or predatory mites (Amblyseius cucumeris) can react sensitively to neem oil. It is therefore extremely important that neem preparations are only used in accordance with the recommendations for use on the packaging or the instruction manual. This will keep the risk as low as possible.

Using neem oil in other ways

The ingredients of neem oil can also be used for our pets. Neem oil can be used to treat wounds or to ward off insects. Neem is not only good for our plants and animals however, we can also use neem ourselves.

Important: Some scientific studies have shown that neem oil treatment can lead to some degree of discomfort and in worst cases, even symptoms like tremors in some cats. For this reason, we advise to consult your vet before using neem oil on your cats or in close vicinity to your cats.

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