Overview:
- What are natural substance biopesticides?
- Types of natural substance biopesticides
- How natural substance biopesticides work: modes of action
- How to apply natural substance biopesticides
What are natural substance biopesticides?
Natural substance biopesticides contain one or more compounds originating from nature. Many of these are botanical oils and plant extracts. They can also originate from other sources such as minerals, animals or fungi. Natural substance biopesticides exclude other biopesticide types, namely microbials and semiochemicals.
The compounds present in natural substance biopesticides can be extracted from the original source or synthesized to mimic them. These products are used to manage pests, diseases, and weeds.
Some examples of natural substance biopesticides are:
- Azafit (ES) contains azadirachtin, a compound derived from the neem plant and can control many insect pests.
- PREV-AM (BR, DE, ES, FR, KE, MX, PT) contains orange oil that can kill mites, insect pests and fungal pathogens.
- FLiPPER (ES, FR, HU, PT, UK) contains unsaturated carboxylic acids extracted from olive oil. It can kill soft-bodied insects, such as aphids.
Types of natural substance biopesticides
Natural substance biopesticides include products containing extracts and oils from botanical and mineral sources. They can also come from animals, algae or fungi.
Natural substances from botanical sources
Botanical extracts and oils can come from different parts of the plant, such as fruit, bark, leaves or seeds. They are primarily used against insect pests, but some can also control plant diseases.
Neem
Neem products derive from the neem tree (Azadirachta indica). They can control various insects, including mealybugs, aphids, thrips, whiteflies and locusts.
The active ingredient of neem is the compound azadirachtin that comes from the seeds. When azadirachtin enters an insect body (by ingestion or physical contact), it prevents it from feeding or growing normally. It also has repellent properties.
Some examples of neem products:
- Socoro (US) is an oil that controls insect pests, mites and plant diseases.
- Azafit (ES) targets insects and mites in their larval stage.
Thyme oil
Thyme oil comes from the leaves of the thyme plant. Thymol is a compound found in thyme oil. It can manage insects by repelling them, and it can also control some fungal diseases in plants.
- An example of a thyme oil product is No path EW (KE), a product that can control pests on ornamental flowers like roses.
Other botanical oils or extracts include garlic extract, citrus oil extracts (orange, lemon, etc.) and eucalyptus oil.
Natural substance biopesticides from mineral sources
These contain compounds like petroleum or its derivatives, for example paraffin, and other compounds like kaolin. They work against insect and plant pathogens as well.
Some examples of mineral-sourced biopesticide products are:
- Lovell (FR) contains paraffin and covers insect and mite pests with a coat of product. It asphyxiates pests that die shortly.
- Surround WP (FR) is based on kaolin, a clay material. It forms a physical barrier on crops, preventing insects from feeding on them. It also repels pests.
Natural substance biopesticides from other sources
Natural substance biopesticides can also be extracted from sources other than minerals and plants. These include animals, algae, bacteria or fungi.
Chitosan
Chitosan is a product derived from chitin, the major component of the rigid ‘skin’ (exoskeleton) of crustaceans. It has antifungal properties and can manage fungal pathogens in plants.
- An example of a chitosan product is Armour-Zen (NZ). a biopesticide based on chitosan. It controls fungal diseases such as grey mould on ornamental flowers. It prevents the spread of fungal diseases by stopping fungal reproduction.
Diatomaceous Earth
Diatomaceous earth consists of fossilized remains of aquatic organisms called diatoms. It is very abrasive and absorbs oils and fats from the skin of insects (the ‘exoskeleton’). Thus, it can control many crawling insects and mites that die from dehydration. You can use it in the field, but its most common use is for stored crops, to prevent infestation by insects like weevils and beetles.
- An example of a Diatomaceous Earth product is Permaguard D-10 (AU) that can control pests on stored grains like barley and wheat.
How do natural substance biopesticides work?
Natural substance biopesticides use many modes of action to control pests and diseases. They can work once they come into contact with the pest or pathogen and when pests ingest them.
The modes of action against pests and plant pathogens are:
- Repellence and anti-feeding: the natural substances can deter insect pests from feeding on or approaching crops. For example, garlic extract emits a strong odour that repels pests.
- Toxicity/lethal activity: the natural substance can cause the death of the pest or pathogen. These can happen in several manners:
- Desiccation: the product dries out the pest or pathogen, leading to its dehydration and death.
- Suffocation: substances like petroleum and vegetable oils can block the respiratory system of insects, which suffocate.
- Neurotoxicity: it disrupts the nervous system of the insect, leading to its paralysis.
- Interference with physiological activities:
- Growth inhibition: some products like neem oil or chitosan stop the growth of the pest or disease. For instance, they can prevent insects from moulting (losing their skin), which is vital for their growth.
- Oviposition deterrence: pests do not lay their eggs on treated crops because they become unsuitable.
How to apply natural substances
Most natural substances come in a liquid formulation or a water-soluble solution, for example, a wettable powder. You can either apply the product directly to your crops or mix it with water first.
The application methods are similar to other biopesticides, such as microbials. These are:
- Foliar application: you can spray or mist the product on plant leaves with standard spraying equipment.
- Seed treatment: the seeds are treated with the natural substance before sowing to protect the plant in its early development.
- Seedling dipping: you can dip seedlings or roots of seedlings in the product mixture.
- Soil application: the product can be applied in the soil by drenching the mixture on the soil or injecting it into the field irrigation system.
Natural substances degrade quickly in the environment, meaning that they have little to no adverse effects on the environment. This also means they may require regular application and should be used when conditions are optimal.
- Read our ‘How to use bioprotection‘ blog to ensure you use the best practices.
