Insecticide and repellent: natural alternatives. It's all in nature !
Insects and other small arthropods are part of nature. Most of the time, they are as harmless as they are important to the balance of nature and the health of our plants. Sometimes, however, the invasion of a particular species can cause problems: in these cases, the insects are considered by man to be pests. In such cases, a radical but, as far as possible, environmentally-friendly solution is needed.
The solution could be to use a natural insecticide. These alternatives do exist. Nature offers us a wide choice of natural substances to combat insects. Effective and reliable products are developed from substances of mineral or plant origin. These sustainable solutions are part of an integrated pest management approach that combines prevention, monitoring and treatment.
Even if they are of natural origin, insecticides must be used with the utmost care and always in accordance with the manufacturer's instructions.
Here is a presentation of the main natural insecticides available in our shop.
A quick reminder : what is an insecticide ?
By definition, an insecticide is a product in the pesticide family, designed to control insects, whether adults, larvae or eggs, crawling or flying. It is generally understood in its broadest form, i.e. with the property of controlling, repelling or killing all so-called harmful insects, including arthropods (which are not insects) : spiders, mites, etc.
Some insecticides are specific to a given species. Others attack all insects without distinction.
A distinction is made between insecticides (designed to kill) and insect repellents, which are products used to scare insects away.
Most chemical insecticides on sale have a significant impact on :
- the environment and biodiversity : by eliminating insects, they also affect the birds and mammals that eat them, natural predators whose disappearance or rarefaction can destabilise an entire ecosystem. The insects targeted may also themselves be predators of another, much more harmful species, which ends up developing freely. The use of insecticides has also been blamed for the decline in the populations of pollinating insects that are vital to biodiversity, from bees to butterflies: without them, plants cannot reproduce. The famous neonicotinoids, in particular, are among the most widely used in the world and are thought to play a major role in the collapse of bee colonies.
- Health : This information is no scoop! The use of, or exposure to, insecticides has potentially serious effects on human and animal health. Repeated exposure could cause neurological, cardiovascular, respiratory and dermatological disorders, and increase the risk of cancer, neurodegenerative diseases, hormonal disturbances and foetal malformations in pregnant women. Although their effects are difficult to quantify, a large part of the scientific community agrees on the dangers of pesticides in general, even at low doses. Even with targeted use, insecticide residues have been found in the vast majority of crops grown for human consumption. They can also contaminate food-producing animals, drinking water supplies to the point of rendering them unfit for consumption, or simply the air we breathe.
But there are also insecticides of natural origin that are authorised and widely used in organic farming and in our gardens. These are the ones we will be describing in this dossier.
Pyrethrum against insects
When it's not being synthesised in a laboratory, pyrethrum is a plant insecticide extracted from the dried flowers of the chrysanthemum plant. This insecticide is also known as Dalmatian pyrethrum (Tanacetum cinerariifolium). Originally from the Adriatic coast, the plant has spread much more widely due to its insecticidal properties, particularly in Africa, where certain countries such as Kenya and Tanzania have turned it into an economically profitable crop. Be careful, however, not to confuse it with African pyrethrum (Anacyclus pyrethrum). It also contains pyrethrins, but in lower proportions.
The term "pyrethrum" refers to the powder extracted from dried chrysanthemum flowers, while the term "pyrethrins" refers to the six active compounds contained in this powder.
Its repellent and insecticidal effects have been known for decades and it is widely used in organic farming. This active ingredient is effective against a wide range of insects: cockroaches, bedbugs, flies, mosquitoes, textile moths, food moths, ants, silverfish mites, hornets, lice, cockroaches, etc.
Pyrethrum extract can be used on its own or in combination with another molecule with a lethal effect and/or with a synergistic agent that significantly increases its lethal action.
Pyrethrum extract acts on the nervous system of insects, causing them to suffer lightning muscle paralysis. It is one of the most powerful knock-down agents.
To find out more about pyrethrum extract, take a look at our dedicated file → See here.
Margosa extract against insects
Margosa extract (or Neem extract) comes from the seed of the Margosa tree, also known as the Neem tree.
It is azadirachtin, the active molecule extracted from Neem oil, that produces the effects on insects. Margosa extract is obtained by a high-tech process (international patent) using carbon dioxide in a supercritical state as the extraction agent.
Margosa extract is effective against a large number of phytophagous insects and mites: in particular whiteflies, caterpillars, aphids, thrips, weevils, webworms, mealybugs, mites, in particular red spiders, mealybugs, a large number of diptera and hymenoptera, as well as all wood-eating insects.
Azadirachtin is the most effective biocide on the market. This natural pesticide is used successfully in agro-ecosystems, especially as it has no impact on the microbial organisms present in the soil. In fact, the WHO and the United Nations Environment Programme recommend its use.
It acts at several levels in the physiology of these insects :
- It paralyses the digestive tract, meaning that the insects can no longer digest what they have ingested: they stop feeding and die.
- It stops larvae moulting, so they never reach the adult stage and die.
- It inhibits sexual reproduction by blocking mating.
The effects of Margosa extract on parasites are not immediate. It may take 2 or 3 days for the insects to die or flee.
To find out more about Margosa extract, take a look at our dedicated file → See here.
Geraniol against insects
Geraniol is a volatile, fragrant molecule naturally present in essential oils derived from plants.
Geraniol is known in particular for its larvicidal and ovicidal properties. It is an active substance used to formulate repellent and insecticide products that are effective against a wide variety of insects and mites such as :
- Mosquitoes, houseflies, blowflies and other diptera, wasps, hornets,
- Cockroaches, earwigs, crickets, ants,
- Coleoptera, Lepidoptera larvae,
- Lice, fleas, dust mites, aphids
- Ticks, etc.
Geraniol in aqueous solution acts in 2 ways on insects, whatever their stage of metamorphosis (egg, larva, adult): by suffocation and by dehydration, acting on the chitin (the insect's protective envelope).
Geraniol is one of the best larvicides and ovicides on the market. It is therefore a product used naturally for preventive flea and tick control in pets, or to reinforce the insecticidal action of a product, or even as a repellent against haematophagous (blood-feeding) insects, in the form of a protective bracelet worn on the wrist.
To find out more about geraniol, take a look at our dedicated dossier → See here.
Diatomaceous earth against insects
Diatoms are unicellular micro-algae enveloped by an external skeleton composed mainly of amorphous silica (transparent and rigid). Fossil deposits of diatom skeletons are known as diatomaceous earth.
Diatomaceous earth is an inert product, free from known harmful substances. After grinding, it has the appearance of talcum powder. Thanks to the specific surface area of its grains and its siliceous skeleton, diatomaceous earth has a number of very interesting properties :
- High absorption capacity: up to 150% of its weight in water.
- The ingestion of silica particles by insects causes lesions in their digestive tract.
The fineness and hardness of the silica particles collected by the insect's bristles cause lesions on its limbs or carapace (walking on diatoms is like walking on broken glass!). This causes the insect to lose body fluids, leading to death from dehydration after a few days. The absorbent properties of diatomaceous earth help this process. As it is totally inert, it provides long-term protection for treated areas, both indoors and out.
Today, diatomaceous earth is probably the safest and most effective insecticide for treating crawling insects in the home. Diatomaceous earth should be spread on the places where insects pass through, but also on their shelters: attics, nooks and crannies, skirting boards, cracks in walls, and generally all types of interstice where pests could take refuge. With its long-term action, diatomaceous earth remains effective as long as it is not affected by damp. In the home, it can be used against a large number of insects as long as they are crawling: bedbugs, cockroaches, silverfish, fleas, red lice, ants, etc.
Although some insects in stored goods may become less sensitive to this biocide over generations, no resistance is known to date. It has an immediate barrier effect and can be used over the long term for both preventive and curative purposes. This insecticide is non-selective. It should therefore be used with care, as it is likely to cause the death of non-target crawling insect species.
To find out more about diatomaceous earth, take a look at our dedicated dossier → See here.
Spinosad against insects
Spinosad is a fermented product derived from a mixture of two toxins (spinosynes A and D) secreted by a soil-dwelling bacterium : Saccharopolyspora spinosa.
Spinosad is not very toxic to mammals, birds, fish and crustaceans. It is, however, highly toxic to bees. Direct application and spraying of this substance near bees and their colonies, as well as near crops in full bloom, should therefore be avoided. It should be used as part of a rational plant protection strategy. This strategy harmoniously combines the priority given to natural beneficials in the garden with a minimum of localised treatments where insects are present, with the aim of re-establishing a balance in favour of natural beneficials.
Spinosad acts as a neurotoxin and is active both by contact and by ingestion, although ingestion is thought to be 5 to 10 times more effective. Its effects are rapid, which is relatively unusual for a biological product. Insects are paralysed and stop feeding. In general, Spinosad is effective against caterpillars, flies and thrips, as well as certain species of beetles, grasshoppers and ants. However, it is not effective against sucking insects or mites (e.g. aphids, whiteflies, leafhoppers).
While the effects of spinosad are rapid, it has little after-effect. This is very good news. It allows auxiliary fauna to re-establish itself quickly after a treatment. On the other hand, this low residual effect means that treatment must be carried out at the most opportune time to ensure optimum efficacy. Evening spraying seems to be the best choice for two reasons: it is in phase with the consumption patterns of defoliating caterpillars and beetle larvae, which are often nocturnal, and it allows the suspension deposited on the leaves to dry more slowly.
Cold against insects
The freezing method is still an excellent way of combating insects in general. At between -18°C and -25°C, these low temperatures will destroy eggs, larvae and adult insects in 48 to 72 hours, depending on the species. Contaminated objects or textiles can easily be treated in this way.
A new generation of cold-acting insecticides now exists.
The cryonics method, for example, is becoming increasingly popular among professionals, particularly in the fight against bedbugs. This process involves spraying either dry ice (a solid form of CO2) at -78°C or liquid nitrogen at -196°C onto areas infested by bed bugs (mattresses, beds, furniture and clothing). The exposed areas are then cooled instantly, evenly and uniformly. The pest has no time to escape and dies immediately.
Deep-freezing is another method proposed by professionals for eliminating insects that have taken up residence in your furniture or other bulky objects. Deep-freezing starts at -30°C. This is the temperature of cold rooms, a temperature at which the cold spreads evenly and rapidly, leaving the insect no chance of survival, even if it is frost-resistant. Wherever the insect has taken refuge, it is doomed to certain death.
Finally, cold paralysis insecticides are another useful innovation for controlling all types of insects: wasps, hornets, cockroaches, spiders, ants, fleas, bedbugs, flies, mosquitoes and moths. They come in aerosol form. These insecticides usually contain a high-precision formula based on liquefied gases (butane, propane). The exit temperature is around -45°C. This means that the insect is instantly paralysed and frozen on contact. It can be used in kitchens and food environments as well as textiles and mattresses. In addition to their lightning-fast elimination, these paralysing insecticides have the advantage of being odourless and leaving no traces or stains on surfaces. On the other hand, as you will have realised, their formulation, which contains no active insecticide substance, is not persistent. Cold paralysis insecticides are ideal for use in sensitive areas such as bedrooms, on textiles and mattresses.
Thuringian bacilli against insects
Thuringian bacilli or Bacillus thuringiensis or more simply BT are bacteria that are found everywhere in nature in small quantities: in the air, in water, in the soil but also on the plants themselves. These bacilli produce a molecule called thuringiensin. These insecticidal bacteria are the most used in the field of organic farming.
There are several different strains. Bacteria therefore attack one type of insect or a single species without directly affecting other insects. There are therefore strains that only attack Boxwood moth caterpillars, Pine Processionary caterpillars, and even mosquito larvae, to name but a few examples. Bacillus thuringiensis can also be used for certain flies, but also beetles such as the Colorado potato beetle and the lily leaf beetle, and of course, butterfly caterpillars such as moths, tortrixes, leaf miners, moths, moths or codling moths .
The effect is limited in time, but radical! Thuringian bacilli produce endotoxins that destroy insect gut cells, while spreading the bacteria throughout the body, creating widespread infection. The insect can no longer feed and dies shortly. The bacillus will continue to "consume" the corpse thereafter.
BTs have the advantage of degrading very quickly by UV rays, heat but also simply in water. The persistence of this type of treatment is therefore almost zero if we refer to current studies. However, Bacillus thurigiensis are not completely safe for warm-blooded animals. We must therefore remain cautious and target.
Did you know ? Some GMO plants have been genetically manipulated to produce the BT toxin themselves and thus create their own insecticide directly within their tissues.
Animal insecticides - Garden auxiliaries
Encouraging biodiversity in the garden means creating an environment conducive to a balance between a varied number of plant and animal species that contribute to life in the garden and help us fight against harmful organisms. The main useful species are: spider, weasel, golden beetle, ladybug, bat, grass snake, toad, lacewing, parasitic wasp, frog, hedgehog, lizard, shrew, bird, raptor, bug, hoverfly. Several solutions are possible to attract these auxiliaries, such as the constitution of diversified country hedges, beds of shrubs, or the construction of shelters.
The main auxiliary insects :
1 - Ladybugs, for example, are renowned for devouring aphids, and widely used in organic farming. It is the larva that is the most voracious since in a day it will eat 150 aphids, the adult only consuming 15-20.
2 - The lacewing : The larva feeds on aphids. The adult according to the species feeds on insects or nectar. Immobile insects such as aphids, cochineal larvae, mites, chiggers in the lawn, whitefly larvae and eggs. For tomatoes that suffer the bites, they become discolored and will be more susceptible to disease. During its development, a lacewing larva can eat 200 to 500 aphids, and up to 10,000 mites. Associated with other auxiliaries (ladybugs for example), lacewings are not only good control predators, but can even participate in the complete "cleaning up" of pest populations. On the other hand, these fragile insects fear rain and wind. They will need shelters such as ivy climbing on a non-fragile support, not risking being smothered.
3 - The hoverfly : Looks a bit like a bee or a 2-winged wasp, 2 cm long and is characterized by hovering. The larvae feed on black aphids, various insects, scab type fungi, rust, the adults being pollinators. Hoverfly larvae eat 80% of garden pests.
Hoverflies, lacewings, ladybugs (in the absence of aphids) are nectarivorous insects, hence the need to plant various nectar-producing flowers all year round, as the development period for aphids is limited.
4 - The cantharide (orange beetle) : Comes out at the end of April at the beginning of May on the umbelliferae (fennel, wild carrot, dill, fennel, etc.) rather white flowers where they feed on nectar and pollen: having a very short proboscis, it is more easy to feed on these flat umbels. Larvae living in the soil are formidable predators for small underground pests. They like places to hide, mulch at the foot of trees, heaps of dry leaves, pieces of wood or stones. A hedge will also be a good refuge against their predators as well as for many other auxiliaries.
5 - The gendarme : Stinging gregarious insect with a soft body, it feeds on the eggs of aphids and other insects, mealybugs. Also involved in the decomposition of plants. Will be attracted by mallows, hibiscuses, a lime tree. In winter, leave the dead leaves fallen at the foot of the shrubs to give them refuge.
6 - The ground beetle : A very fast insect, it has a fluo-coloured, bluish-green, black shell and is provided with mandibles with which it catches its prey. Very large predator, it eats white grubs, insects emerging from the ground in the spring such as codling moth, snails, slugs. It settles in the plant mulch, shelters there but also likes beer. So be careful when using the slug trap.
Manure, infusions and decoctions against insects
Some plants in our garden can help us in our fight against insects. All you have to do is prepare manure, decoctions or infusions depending on the plant and the desired effect.
Fern manure is an insecticide and repellent for aphids, leafhoppers, wireworms and even slugs. Manure can be made from eagle fern (Pteridium aquilinum) or male fern (Dryopteris filix-mas). It is then used pure. In other cases, it can be diluted to 10%. Fern manure is obtained by fermenting 100 g of plants per liter of water, to be adapted according to your needs.
We can also cite nettle, wormwood, tansy or rhubarb manure, which have very effective insect-repellent properties.
The infusions are simple to make but effective. Garlic infusion protects against leek moth and carrot fly, chamomile infusion against aphids, codling moth and imported cabbageworm.
You can make decoctions using several different plants, but for an insecticidal or repellent effect, here are the most effective: garlic decoction against peach leaf curl; decoction of tansy as a repellent against pierids, moths, flea beetles and aphids; decoction of lavender against ants, decoction of lavandin and clove against wasps and mosquitoes; and the decoction of wormwood as a repellent against ants, aphids, codling moths and pierids.
Vegetable oils against insects
Some vegetable oils have extremely interesting properties to fight against insects.
Coconut oil : Coconut oil itself is not an insecticide. On the other hand, the specific fatty acids that compose it are at the origin of this effectiveness against blood-sucking insects. Among them are lauric, capric and caprylic acids as well as their corresponding methyl esters. To prove this, scientists locked fatty acids in capsules containing a starch-based preparation. Following numerous tests on cattle for more than 96 hours, this natural preparation has proven to be protective against mosquitoes. Even more surprisingly, the insecticides were only 50% effective compared to 95% for the natural remedy based on coconut oil. Indeed, conventional insecticides lost their effectiveness after three days while coconut oil was protective for about two weeks. Coconut oil is now also found in formulations against head lice. The coconut oil then forms an occlusive film which asphyxiates the insect.
Sesame oil : Vegetable sesame oil has a biochemical action. It also has a technological action with the insecticidal active ingredient of a formula. It slows down its evaporation, increases its persistence and the effectiveness of the product by disturbing gaseous exchanges (breathing) as well as the function and structure of the cell membrane. Its toxic action on insects is more physical than chemical. Sesame vegetable oil contains natural molecules close to PBO (piperonyl butoxide: a synthetic synergizer widely used in conventional insecticides) in terms of structure.
Rapeseed oil : Very effective on the eggs and larvae of many insects but also on aphids, mealybugs, mites and whiteflies. Its action is simple: it coats the parasites with a lipid film, which, asphyxiated, can no longer move or feed. Their death by suffocation occurs quickly after treatment. It is a purely physical action. Effectively controls all stages of development (eggs, larvae, adults) of the targeted insect pest. Non-toxic to pets and humans, safe for the environment. Usable in organic farming.
Essential oils against insects
Essential oils can make life difficult for insects. They are composed of various molecules, such as aldehydes (citrals, citronellal), monoterpene alcohols (citronellol) and phenols (eugenol). At present, these natural substances are the subject of much scientific research, with the aim of keeping away or regulating certain populations of insects. In hot and humid regions, the stakes are high. We present below those that seem to us the most common and effective.
Lemon Eucalyptus : Lemon eucalyptus oil (also called Eucalyptus citriodora) is a plant extract concentrated in P-menthane-1,8 diol (also called Citriodiol®). This substance has a strong repellent effect against many pests (mosquitoes, ticks, lice, flies, snakes, small mammals, etc.). Its activity is comparable to the 3 main substances on the market (DEET, Icaridin and IR3535™). Lemon eucalyptus oil is the only substance of natural origin that provides a repellent and significantly long-lasting effect.
The citronellal and citronellol components of this essential oil help keep insects away and kill certain mosquito larvae. It is even more concentrated in citronellal than Lemongrass, which increases its repellent effect. In addition, this oil is an excellent anti-inflammatory which at the same time helps to soothe insect bites.
Lemongrass : Lemongrass essential oil contains citronellol and geraniol, two naturally active mosquito repellent molecules. It disrupts the nervous system of insects that prefer to stay away. The lemony smell that emanates from it strongly displeases them. Its calming and soothing properties will make it your ally for mosquito-free nights. Last advantage: it purifies the ambient air thanks to its content of terpene alcohols.
Lavandin : Lavandin is known for its very characteristic scent, this smell is not appreciated by insects, particularly flies, moths and wasps.
Lavander : Lavender quickly relieves insect bites, it has analgesic and calming properties thanks to the linalool it contains. But, this essential oil is also well known for its repellent activity.
Peppermint : Menthol, an antiviral and antibacterial component, present in peppermint essential oil is very effective in scaring away wasps in particular. The cold effect caused by the application of this oil on the skin also helps relieve an insect bite.
Rose Geranium : Another essential oil well known for its mosquito repellent properties is Rose Geranium essential oil. Like Java Lemongrass, it is also composed of geraniol, a molecule that has significant repellent properties. And not content to repel mosquitoes, it also relieves in case of bites, by facilitating healing. Rose geranium essential oil can be used by pregnant (over 5 months) and breastfeeding women, as well as by children from 6 months.
Basil : Among the properties of the essential oil of Basil that must be remembered, we find its antiparasitic action. In addition, its constituents methylcinnamate, methylchavicol, ocimène, cineole and linalool have a recognized insecticidal action.