When purins, decoctions and other organic treatments don’t help with certain diseases or pests, essential oils can be a great help in the garden, but always used with caution because they are highly concentrated in active principles.
Which essential oils ?
The essential oil of garlic (Alium sativum) has fungicidal, repellent and insecticidal properties. It is used against powdery mildew, but also against parasites such as defoliating caterpillars, ants or aphids.
Clove oil (Eugenia caryophyllus) fights against mildew, fumagine but also has a repulsive action on carrot flies, onion flies and leek miners.
The essential oil of juniper (Juniperus communis) repels the codling moth, a major pest of plum trees.
The essential oil of wild oregano (Origanum compactum) is very effective against mildew, fumagina, scab, but also monilosis.
The essential oil of tea tree fights against mildew in the treatment of vines.
The essential oil of mountain savory (Satureja montana) is very effective against fumaginia, mildew or scab.
As for citrus essential oils, lemon, sweet orange or grapefruit have a positive action against mildew and a repulsive action against CPB.
The essential oil of tansy (Chrysanthemum vulgare thujanoliferum) is very effective against rust.
What are the active ingredients of essential oils on plants?
The flavonoids contained in some oils block the development of fungi, while the acids help the plant grow and make it stronger against pest attacks.
Lactones inhibit the development of certain parasites such as mites, nematodes or various insects.
The esters also prevent the development of pests while repelling them.
This cocktail of active properties makes essential oils very effective in the vegetable garden as well as in the ornamental garden.
The use of essential oils in the garden
As for humans, essential oils must be handled with care on plants. Very concentrated, they are used in a curative rather than preventive way by respecting the doses not to burn the foliage. They are applied by spraying after dilution, but they cannot be mixed with water. They must be mixed with clay milk or a vegetable oil such as rapeseed, or even black soap. One then counts 20 to 25 drops of essential oils for one liter of liquid.