Description
Essential Oils for the Home & Garden
If you are trying to limit your exposure to toxic and synthetic chemicals in your garden and home essential oils can be valuable tools. They are well-known for their wellness virtues for humans, and can also be precious allies to protect your plants naturally and ecologically.
These oils have been used for thousands of years for their medicinal and cosmetic benefits, and their power lies in the hundreds of chemical constituents they contain. Whether you are trying to chase away garden pests from your vegetable or flower garden, protect your plants against diseases, or simply to improve their overall health, we can use these natural defences to our advantage in both our home and garden, using products you can store in your medicine chest. How cool is that!
Tea Tree Essential Oil
Tea Tree Essential Oil (Melaleuca alternifolia) is a thin, clear to pale yellow oil, steam-distilled from the leaves of responsibly grown Australian tea trees. Known for its sharp, medicinal, and slightly spicy aroma, tea tree oil has been used traditionally for its powerful antimicrobial and cleansing properties.
In the Garden
Tea Tree essential oil is utilized as a natural biopesticide. It serves as a botanical alternative to synthetic chemicals for controlling Insects, Mites, Fungi, and Nematodes.
Its strong camphor scent makes the perfect insect repellent against Ants, Flies, Mosquitoes, Cockroaches, Bed Bugs, Rodents, Spiders, Ticks and Bed Bugs.
Lepidopteran Pests
Results revealed that tea tree essential oil has the potential to control Lepidopteran pest species.
Lepidopteran pests comprise moths and butterflies whose larval stages (caterpillars) are major agricultural and forestry defoliators. They inflict massive global economic losses by feeding on foliage, boring into stems or fruit, and destroying crops. Some of the most destructive and economically significant lepidopteran pest species in South African include:
African Bollworm (Helicoverpa armigera) whose larvae aggressively attack vegetables, maize, sorghum, and cotton.
False Codling Moth (Thaumatotibia leucotreta) is a severe pest of citrus, stone fruits, and macadamia nuts in South Africa.
Fall Armyworm (Spodoptera frugiperda) is a highly invasive defoliator that aggressively attacks cereal crops like maize.
Diamondback Moth (Plutella xylostella) feeds primarily on cruciferous vegetables like cabbage and broccoli.
Sugarcane Borer (Eldana saccharina) is a prominent stem borer affecting sugarcane and maize in Africa.
Macadamia Nut Borer (Thaumatotibia batrachopa) frequently damages the husk and kernel of macadamia nuts.
Greenhouse Whitefly (Trialeurodes vaporariorum)
Greenhouse Whitefly is considered one of the major agricultural pests affecting both greenhouse vegetable crops and ornamental plants across the country. It is highly polyphagous and targets hundreds of plant species, particularly Tomatoes, Sweet Peppers, Eggplants, Cucumbers, Beans, and various ornamental flowers like Poinsettias and Roses. It frequently co-exists with the Tobacco Whitefly (Bemisia tabaci).
The whitefly extracts sap from leaves, which causes reduced plant vigour. It also secretes sticky “honeydew” that promotes the growth of black sooty mould, damaging crop quality.
When vaporised in greenhouses, Tagetes essential oil showed insecticidal activities against eggs, nymphs, and adults of Trialeurodes vaporariorum without direct contact.
As a Deterrent
Ants and Flies
All sorts of ants are repelled by pungent smell of tea tree oil. Biting flies and midges also keep clear away.
Mosquitoes
Tea tree essential oil repels mosquitoes. Its strong, pungent aroma masks the human scents that attract bugs. For some people, tea tree oil works as an impressive mosquito repellent, even better than DEET and citronella. However, it is not as long-lasting as synthetic options like DEET and must be reapplied frequently.
Cockroaches
Cockroaches find the pungent odour of tea tree oil highly unpleasant. It can mask the smell of their food sources and the pheromones they rely on to navigate. To use it as a deterrent, many homeowners mix roughly 10 to 15 drops of tea tree oil in an emulsifier like liquid soap in a cup of water in a spray bottle and apply it to cracks, crevices, and entry points.
Spiders
Spiders absolutely dislike tea tree oil. The strong, medicinal scent contains natural compounds that disrupt their sensory organs, making them want to avoid the area.
Rodents
Rats and other rodents do not like the smell of tea tree oil. Its potent medicinal scent is highly off-putting to rodents and is sometimes used as a temporary natural deterrent to discourage them from nesting or traveling through specific areas. This is only a temporary fix, as, like peppermint and eucalyptus, tea tree oil only provides short-term odour deterrence, and because the scent fades quickly and rats can adapt to it, essential oils are not a reliable way to eliminate a rat infestation on their own.
If you are dealing with a serious rodent problem, natural scents should be used as a supporting method alongside structural pest-proofing and traps. For serious or ongoing infestations, professional pest control is strongly recommended.
Bed Bugs
Tea tree oil contains the compound terpinen-4-ol, which research suggests can kill bed bugs and other small pests. Terpinen-4-ol might also disrupt the reproductive cycle of bed bugs.
Ticks
It is used as a spatial repellent to deter insects like cattle ticks.
As a Fungicide
Tea tree oil, in particular, is known for its Antibacterial and Antifungal properties, which makes it an excellent choice for protecting against and fighting plant diseases like Blight and Powdery Mildew, Rust, Blight, and Leafspot Diseases.
Grey Mould (Botritis cinerea)
Research has shown the tea tree essential oil is efficient against Botrytis cinerea, a very common disease, causing a soft decay of plant tissues accompanied by a growth of fuzzy grey-brown mould.
It is a primary pre-harvest and post-harvest threat in South African vineyards, particularly in the table Grape production regions of the Western Cape. It was officially documented as a pathogen affecting South African Blueberry orchards in the Stellenbosch region. The fungus also frequently occurs in Pear blossoms and on Stone Fruit in Western Cape orchards, causing blossom blight and post-harvest decay.
It also affects many plants grown under glass where conditions are humid.
Black Bread Mould (Rhizopus stolonifera)
Black bread mould occurs widely across South Africa. It is a cosmopolitan fungus found naturally in the soil, in indoor environments, and on decaying organic matter.
It is a major postharvest pathogen causing Rhizopus soft rot on various fruits, including Stone Fruit in the Western Cape, Avocados in Limpopo, and Grapes. Studies have frequently isolated the mould from South African stock feeds and grains, as well as from soil samples in arid regions like the Karoo.
Black Mould (Aspergillus niger)
This ubiquitous fungus is widely recognized for its distinctive, dark-coloured spores that appear as powdery black growth on surfaces. It is very commonly isolated across South Africa, and can be found in local soils, decaying vegetation, and indoor environments. It also regularly appears as a contaminant in food crops and agricultural products. Therefore its prevalence and localized distribution should be viewed in several contexts. Although black mould is an agricultural pest, it is also a vital part of our ecosystems and is found naturally across local landscapes, contributing to the country’s diverse range of fungal strains, with almost 500 catalogued in South African fungal databases, all of which need to be protected.
Post-harvest Diseases
Black Mould is also known to cause post-harvest diseases like black mould in regional agricultural crops and is notorious for causing food spoilage on produce like Onions, Grapes, and Apricots. Good antifungal activity of the essential oil has also been demonstrated against black mould in grapes.
Post-Harvest Preservation:
It acts as an effective fumigant and contact insecticide against stored-grain pests, such as the Confused Flour Beetle and the Corn Weevil. It disrupts insect’s energy metabolism and causes mortality.
The oil’s volatile compounds prevent fungal decay, making it a viable, eco-friendly agent for preserving stored grains and food products.
Protection
Add a few drops of pure oil to porous clay pucks or sachets and place them inside sealed storage containers. The released fumes safely repel beetles without diminishing seed viability or germination rates.
The Cotton Wool Method listed below is also effective in pantries and small storage spaces.
Garden Spray
Mix 10-20 drops of the essential oil in 1 Litre of water with an emulsifier. Shake well, and regularly while spraying down the foliage of plants or surfaces.
In the Home
Tea Tree Essential Oil is a clear to pale yellow, thin oil steam-distilled from the leaves of the Australian tea tree. Known for its sharp, medicinal, and slightly spicy aroma, Tea Tree oil has been used traditionally for its powerful antimicrobial and cleansing properties.
It is a popular choice in natural skin care and wellness for supporting healthy skin, respiratory health, and immune function. Its fresh, penetrating scent makes it a versatile top to middle note in blends, often paired with other herbal or citrus oils.
When diffused indoor the essential oil will deter many household pests.
- Add a few drops to a diffuser to create a peaceful, meditative atmosphere.
- Dilute with carrier oil for use in massages or skincare applications.
- Combine with Epsom salts and other relaxing oils for a deeply calming bath soak.
How to Use Essential Oils for Pest Control
When it comes to organic gardening, prevention is better than cure, and spraying crops regularly with essential oils to prevent insect infestation and disease is the most effective method. This will not only chase pests away, but also make your garden smell great!
Always use pure essential oils, and because they are so potent, always dilute them first.
How to dilute essential oils
One of the drawbacks of using essential oils in the garden is that the levels of terpenes and other constituents can vary greatly depending on the region where the plants are grown, genetics, climate and other seasonal factors. Therefore, maintaining consistency in the chemical profile of the oils is hard.
For example, Rosemary oil extracted from plants growing in two different regions of Italy will contain varying levels of α-pinene, ranging from 11% to 36%. Another study showed that essential oils extracted from different chemotypes of garden thyme did not have the same toxicity against the bean weevil.
This is the reason why, if you look for exact recipes for the oil you wish to use in the garden, you will find many different quantities of oil versus water used.
Another factor to take into account is the actual number of drops in a milliliter can vary greatly depending on the thickness of the liquid: Thicker liquids like essential oils produce larger drops, meaning it takes fewer drops to make 1mL. Different dropper bottles or droppers also have varying nozzle sizes, which changes the volume of a single drop.
In standard pharmaceutical measurements, 1 mL is equal to approximately 20 drops (meaning 1 drop is about 0.05 mL). Therefore, 10 drops are typically equal to about 0.5 mL.
This is why physicians do not rely on counting drops, as this can lead to incorrect dosing. Instead they use an oral syringe, a graduated measuring cup, or the specific dropper provided with the medicine.
CAUTION:
Because the actual number of drops in a millilitre can vary greatly depending on the thickness of the liquid and varying nozzle sizes, which changes the volume of a single drop, I recommend starting with the lowest recommended dosage. You can always increase it later.
Preventative Spraying
A general guideline when mixing sprays to deter insects, and for anti-fungus protection is to mix 4–8 drops of Essential Oil in 1 Litre of water with an emulsifier.
Garden Sprays
At certain times of the year various pests and diseases will be more prevalent, so for stronger protection dosages can be increased.
Generally you will find recommended dosages are between 10-20 drops per Litre of water.
Always Test Sprays First
Unless you apply very high doses of essential oils, they are perfectly safe to use in the garden. However, because the strengths of essential oils vary, to ensure they do not cause leaf burn, it’s important to always test your spray on a small, isolated area of the plant first. Wait at least 24 hours to check for damage before applying it everywhere.
A good method of remembering which leaves you tested your spray on is to tie string or ribbon onto the stems that have been sprayed.
Take Notes
Taking note of which plants were tested and the dosages used, will soon give you a good indication of the strengths your plants need for protection.
Mixing your spray
The Emulsifier:
Soap is essential as an emulsifier as essential oils do not mix with water and will float to the top, potentially burning your plants. A gentle liquid dish soap, pure liquid Castile or Black soap can be used.
Approximately one teaspoon of liquid soap emulsifier is used in one litre of water. Witch hazel, Vodka, or apple cider vinegar also emulsifies oil and water.
The Method:
In a small glass container, mix your essential oils with your emulsifier, then add some of the water and stir well. Warming the water helps with emulsification. Add the oil mix to the spray bottle with the rest of the warm water. Agitate well and also regularly whilst spraying.
Applying your Oils
Spraying in the middle of a hot, sunny day can cause leaf burn, so always apply the mixture in the cool of early morning or late afternoon. Remember to agitate the spray bottle well before use, and regularly while spraying. Ensure that you spray underneath the leaves where insects commonly hide.
During the cooler times of the day beneficial daytime pollinators are not that active. Never spray plants if you can see beneficial pollinators like bees around the plants. Even organic sprays can be abused in the garden, so as they say “everything in moderation”.
NOTE: The strength of the oils will evaporate, so reapply to plants after rain, every 2 weeks, or as needed.
Cotton Ball Method
To target specific insects in large numbers, like ant hills or rodent burrows, take some cotton balls and add a few drops of essential oils to them. Place the cotton ball right onto the ant hill, burrow or other insect grouping. This will cause them to relocate immediately. If that doesn’t work immediately you should repeat the process using a stronger solution.
You can also rub the oils onto any hard surfaces to create a long-lasting barrier.
Hanging Strips to Deter Pests
Add essential oils to a bowl of warm water and soak strips of pretty material or ribbon in the water before hanging onto the branches of fruit trees, or near edible gardens and ornamental shrubs.
Is there a waiting period before harvesting?
You should not eat vegetables and fruits immediately after spraying them with essential oils. These oils are highly concentrated and consuming them without a waiting period or proper cleaning can cause digestive upset, inflammation, or irritation of the mouth and oesophagus.
Essential oils degrade in sunlight and waiting 24 hours should be sufficient. Ensure that you always wash your food well and all will be fine.
Storing Essential Oil Mixes
Try to mix up only sufficient spray to use in a day, or within 24 hours of mixing. Once exposed to water and oxygen, oil-based garden sprays begin to separate, degrade, and lose their effectiveness.
If you do have any left-over, store it in a glass bottle in a cool, dark place, not in your plastic spray bottle, as essential oils break down quicker in plastic. Agitate well before using again.
