Organic gardening: Essential oils as biological pesticides for indoor and outdoor gardening
vegetables, herbs, fruits, ornamental tree, flower garden, succulents, turf grass, indoor plants
by Dr. Silke Will
Do it Yourself and share your essential oils with your plants
Hundreds of different essential oils were tested for their potential as biological pesticides with promising results. They are already used globally for organic farming. Most of the essential oils are also well known for human aromatherapy and found in many households. This could be a nice opportunity to share your essential oils with your plants. But, the effect can differ within plant species, method of application and other factors. Therefore, it is a great opportunity to figure out what works on your plants. Within my next blogs, you will learn how to create a perfect formulation with your essential oils and figure out what helps best on your plants.
The demand of biological pesticides
Organic or biological pesticides are gaining extreme importance for organic food production, horticulture and agriculture. The green revolution brings more awareness worldwide for producing and consuming environmental friendly products. Chemical pesticides are a major threat to nature, including human, animals, waterways and the ocean. It is estimated that about 2.3 million tons of chemical pesticides are used in modern crop production each year. The worldwide environmental damage reaches 100 billion USD annually.
Plants naturally produce compounds as a defense against pests for their survival. Healthy plants are usually able to protect themself and overcome the infestation. These natural defense systems of plants can be disturbed by natural occurrences or by humans.
Unfavorable weather conditions, such as heat, drought, high radiation, can weaken plants and make them more prone to pests and diseases. Especially plants grown outside their natural environment lack an adaptation to the environmental condition and need more care for survival.
Beside these natural disturbances human made problems take a much bigger part. In the history of breeding the focus was to create plant varieties for specific purposes, e.g. ornamental plants for nice flowers and leaves, vegetables and fruits for size and taste. Breeding for specific purposes are often accompanied by the loss of other characteristics. Especially in food crops the bitter tasting compounds were replaced by more sweet and adorable compounds. The compounds that act bitter or astringent often had the function of pest defense.
Factors influencing the pressure of insects and pests on plants:
Essential Oils as pesticides:
Biological pest control starts by supplying plants with beneficial compounds that help strengthen the plants. Seaweed extract has shown to be one of the most effective biostimulants for promoting the natural defence system of plants. Applied as foliar fertilizer, seaweed acts as a natural protection shield. The positive effects are also triggered by the essential oils which are present in seaweed.
Essential oils as biological pesticides are used either single or in combination in a broad spectrum of applications. The number of commercial products based on essential oils is steadily increasing globally. The table below shows a selection of essential oils used in commercial products either single or in combination for different plant species, such as vegetables, herbs, fruits, ornamental trees, flower gardens, succulents, turf grass and indoor plants.
Table 1: Selection of essential oils for specific pests and diseases
Category of pest and disease
Name
Essential oils
Fungus
Powdery mildew
Sweet orange, cinnamon, mint, rosemary, grapefruit, garlic
Botrytis
Oregano, marjoram, thyme, lemongrass, garlic
Leaf spot disease
Thyme, spearmint, garlic
Fusarium
Lavender, eucalyptus, marjoram, oregano
Sukking insects
Spider mites
Thyme, glove, patchouli, peppermint, lemongrass, cinnamon, rosemary, garlic
Thrips
Sweet orange, thyme, clove, garlic, lemongrass, basil, cinnamon, eucalyptus
Mealybugs
Eucalyptus, clove, cinnamon, rosemary, orange
Whitefly
Clove, cinnamon, rosemary
Aphids
Eucalyptus, basil, peppermint, mint, Ocimum basilicum, anise, lavender, clove, cinnamon, rosemary
Turf management: ants, ticks, fleas
Grubs, ants, ticks, fleas
Cedar wood, garlic and lemongrass
