Last updated on October 23rd, 2023 at 08:19 pm
We have already talked about natural insecticides in other Agrohuerto posts, but today we will make a general review in which we will see 10 of the most used natural preparations in organic gardens to control pests.
Insects such as aphids or whiteflies, mites such as red spider mites or mammals such as rodents can become crop pests and ruin our harvest. Therefore, we must prevent their appearance or control them with insecticides and pesticides like the ones we will see today.
These ecological remedies are environmentally and health friendly. Natural insecticides are used to fight pests naturally in organic gardens and orchards, where artificial chemicals cannot be used.
What are natural insecticides?
Natural insecticides are preparations used in organic farming to fight crop pests.
These natural insecticides can be made from plant extracts, from microorganisms that kill pests (such as some bacteria and fungi used in biological control), or from natural products of mineral origin, such as sulfur.
There is a wide variety of natural insecticides for organic gardening. Most can be purchased in garden stores and other specialized stores, but some can also be prepared at home.
In any case, all natural insecticides have something in common, and that is that they are not synthetic chemical products. On the contrary, these insecticides are composed of natural ingredients (either organic -such as plants-, or inorganic -such as sulfur powder and mineral oils that we will see in today’s post-).
Benefits of natural pesticides
The benefit of using these products lies not only in the environmental aspect (being natural products they will not pollute the air, soil or nearby waters -aquifers or water from wells, lakes, ponds…), but there are also direct benefits for people.
Organic gardening has multiple health benefits… The main one is that the products we harvest are much more natural and have no traces of chemicals or poisons for pests. If, instead of using these traditional chemicals, we use these natural insecticides, we will be protecting not only biodiversity and the environment, but also our own health.
Below are several preparations that can be used as natural pesticides for plants. (Some of these organic insecticides can be prepared at home, and others are easy to find on the Internet or in specialized stores).
- Neem tree oil and other plant oils
Azadirachtin is the active ingredient of “Neem oil”. This compound is extracted from the seed inside the fruit of the Neem tree (scientific name: Azadiratcha indica).
Neem oil is widely used in organic gardening because it is a natural broad spectrum insecticide that is effective against several pests: aphids, mites (such as red spider mites and white spider mites), whiteflies, nematodes, lepidoptera, cottony mealybugs, thrips…
Another type of vegetable oil useful as a natural insecticide is peppermint oil. Recently one of our readers told us in one of the blog comment threads that peppermint oil is an effective repellent of mice and other rodents that can become a pest in the garden.
- Kerosene and other mineral oils
Kerosene is a natural insecticide against common pests such as aphids, spider mites, whiteflies, mealybugs and thrips. Kerosene oil leaves a waxy coating on insects, preventing them from breathing until they die. Dilute a small spoonful of liquid kerosene in 5 liters of water and spray the solution on the insects.
Insecticidal mineral oils known as “summer oil” or “winter oil” are also natural broad-spectrum insecticides. That is, they are used to fight various types of pests. They are usually made with kerosene oil or other hydrocarbons.
- Homemade garlic and onion spray
Garlic and onion are powerful bactericides and fungicides, so preparations made with these plants will help prevent and cure diseases caused by fungi and bacteria. But this preparation is not only effective in curing common garden plant diseases, it can also be used to make natural insecticides against pests such as aphids and spider mites.
Idea to prepare a homemade “garlic and onion spray”: mix five or six cloves of crushed garlic with half a large onion or a medium-sized onion in pieces and add a liter of water. Let stand for 24 hours. Then boil for 20 minutes over low heat and strain the decoction.
Hot peppers can also be added to this homemade natural insecticide. In the community garden Sanyuanli Community Garden, in Beijing, they made macerations with garlic and chili peppers to prepare natural insecticides.
- Pyrethrum
Pyrethrum is a natural powdered pesticide prepared from extracts of the flowers of Chrisantemun cinerarifolium or Anacyclus pyrethrum.
Pyrethrum is used to fight such common pests as aphids, whiteflies and spider mites. A drawback of pyrethrum is that it is also toxic to beneficial insects such as bees, so it should be used sparingly and very occasionally. It is also necessary to
It is also necessary to respect its mode of use, taking into account that it must be applied in low concentration – maximum 25% – so it must be mixed with another powder before application (talcum powder for example) or dissolved in liquid organic solvents that facilitate its application.
- Rotenone
Rotenone is another natural insecticide that comes from plants. It is obtained from the roots of the Derris elliptica plant.
It is effective against pests such as beetles, thrips, caterpillars, mites and aphids. It is applied in the same way as pyrethrum: sprinkled or diluted.
- Horsetail slurry
Horsetail is one of the most widely used plants for natural remedies against pests and diseases in organic gardens. It is very effective against fungi in the garden, but it is also useful to repel snails and slugs and to fight against pests such as aphids and spider mites.
Horsetail slurry can be made by leaving several of these plants to macerate in a container with water (as in the picture above) or you can also make an infusion or decoction at home. Boil 50 grams of dried horsetail (or 100 grams if fresh) in 5 liters of water for one hour. After letting it stand until it cools, strain it through a sieve and spray the decoction diluted with 20% water on the plants.
- Quassia
Like pyrethrum, this is a natural powdered pesticide that is also obtained from a plant. In this case, quassia comes from the wood or bark of the Quassia amara tree.
This natural product prevents several common pests such as the potato beetle or aphid.
- Soapy water
The traditional “grandmother’s soap” or homemade soap. It can be purchased but must be all natural and made with potash (not soda, which is very corrosive to plants). Use a grater to make small particles and boil it in a little water so that it dissolves well. Then add one liter of water for every 30-40 g of soap and spray it on any insects, eggs or spider webs you see (best applied at dusk as it should not be exposed to the sun when freshly applied).
It is effective against aphids, whiteflies, thrips, mealybugs, red spider mites and also against some fungi such as black leaf spot or botrytis…
- Sulfur
Sulfur powder or micronized sulfur is used in organic gardening as a natural fungicide against powdery mildew and other common fungi. But it is also effective against pests, so it is used to repel insects in general.
It can be applied by sprinkling it directly, although it adheres better if mixed with a specific liquid solvent for this use. You can mix the powdered sulfur with a liquid adherent-dispersant, with these two liquids separately, or use “wettable sulfur” and mix it with water. It should be applied at a temperature between 10 and 25 ºC (on hot days better at dusk).
- Bacillus thuringiensis and other natural insecticides prepared from bacteria and fungi.
Biological control is the use of organisms or living beings to control pests and diseases. It is an environmentally friendly method widely used in organic farming.
This biological control includes the use of repellent plants, insects that eat pests, but also preparations made from microorganisms (such as bacteria and fungi) that are pathogenic for pests and end up eliminating them.
An example are preparations with the bacterium Bacillus thuringiensis, which are used to eliminate lepidopteran pests – moths and butterflies and their larvae, caterpillars – (such as Tuta absoluta, the cabbage butterfly…). It is a powder containing thousands of colonies of this bacterium and is applied diluted in water and sprayed on plants.
There are other natural insecticides for pest control with microorganisms. For example, the fungus Beauveria bassiana is used to prepare pesticides effective against insects such as whiteflies, aphids, bedbugs and weevils. And the bacterium Saccharopolyspora spinosa is used to prepare the well-known Spinosad, against pests such as olive fruit flies, thrips or lepidoptera.
I hope you have found this list of natural insecticides for the organic garden useful. If you know other organic pesticides for pests and diseases or if you have any questions, do not hesitate to use the comments thread below.
In addition to using natural insecticides, it is important to follow other integrated pest management techniques to kill unwanted insects. Crop rotation and beneficial associations, the use of local varieties or the use of biostimulants are some of them… Find out more in the article on Integrated Pest Management: What is it and main techniques.