Biocontrol

Technical articles

Biodiversity

Ladybug larva eating aphids

Biocontrol represents all methods of crops protection relying on natural regulation mechanisms of bio-aggressors. It aims to protect plants from biotic stresses by favoring the use of mechanisms and interactions that govern relationships between species in the natural world. Thus, it is based on managing the balance of pest populations rather than eradicating them. In this sense, biocontrol is part of Integrated Biological Protection (IBP) techniques, alongside integrated pest management and biological control.

Biocontrol aims to contribute to the triple performance of agricultural holdings:

• Economically: the emergence of solutions with predictable efficacy and acceptable cost;
• Environmentally: solutions with fewer drawbacks than sole use of chemicals;
• Socially: use that does not impose excessive workloads and does not threaten applicators' health.

What is biocontrol?

The definition of biocontrol products is framed by the Rural Code (art.L.253-6). It concerns "agents and products using natural mechanisms within integrated pest management of enemies of crops." This technical approach is part of a national action program aiming for objective the reduction of phytopharmaceutical products, as a response to "human health and environmental" challenges. However, some biocontrol products have existed for over 30 years (bacillus th.).

Biocontrol thus groups crop protection methods taking into account:

• the interactions between cultivated plants, bioaggressors and auxiliaries
• the regulation capacity of living organisms present in the local agricultural environment
• the implementation of living agents or derived from living organisms used in direct or indirect control

Biocontrol is often combined with other actions:

• Choosing crops and varieties to minimize pest pressure
• Increasing the activity of generalist auxiliaries or certain birds (planting hedges) and ecosystem services
• Implementing living or derived agents: biocontrol products

Key figures

Biocontrol is more or less developed depending on the crops, as shown by these figures published by IBMA:

• 75% of tomato and cucumber greenhouse areas are protected by insect auxiliaries.
• 50% of apple and pear orchard areas are protected thanks to the use of pheromones and confusion techniques.
• 5% of rapeseed areas are protected by using a microorganism as a biological fungicide.
• 2% of corn areas are subject to control against the borer with auxiliary insects.

What are biocontrol products?

Biocontrol products are defined as agents and products using natural mechanisms within integrated pest management against crop enemies.

They include 4 categories:

• macroorganisms (invertebrate auxiliaries such as insects, mites or nematodes)

Example: Trichogrammes against the European corn borer

• microorganisms (fungi, bacteria or viruses)

Example: A fungus (Coniothyrium minitans) against sclerotinia of rapeseed

• chemical mediators such as pheromones and kairomones

Example: Control of the weevil of faba bean

• natural substances of plant, animal or mineral origin.

Example: Kaolin against the weevil of faba bean

Microorganisms, chemical mediators and natural substances are considered by regulation as phytopharmaceutical products, thus subject to Regulation EC 1107/2009 and requiring marketing authorization, whereas macroorganisms are subject to specific regulations for this type of product.

Uses of biocontrol products

The use of biocontrol products differs from that of a conventional pesticide. Indeed, they are often used in a more preventive than curative way on light to moderate infestations. Often, their combination with a conventional pesticide is the winning formula: the biocontrol agent will have controlled the pests or disease effectively enough during the season so that the quantity and frequency of chemical pesticide use is drastically reduced.

Thus, biocontrol products can be involved in different crop management strategies:

• Some biocontrol products participate in the redesign of the system when implemented reasonably, upstream of sowing with other levers such as rotation, soil work, varietal choice, sowing date, sowing density... In this case, these products aim to reduce bioaggressor pressure.

• If redesign levers are insufficient and a bioaggressor exceeds the damage threshold, intervention is necessary. Then, a substitution solution to chemical products is sought. This can be mechanical weeding on weeds or a biocontrol product. Note, however, that thresholds used with biocontrol solutions may differ from those used with synthetic products.

Evaluation selon la grille d'analyse ESR : Substitution-Reconception

Biocontrol and IFT

Currently, biocontrol products are counted in the overall IFT, which includes all products used (conventional phytosanitary products and biocontrol products). A biocontrol product is counted as a conventional product but can also be calculated separately (biocontrol IFT).

Macroorganisms

Visible to the naked eye, macroorganisms are living, invertebrate organisms, insects, mites or nematodes used to exert direct or indirect pressure on pest populations. They are listed on a list (decree of 26 February 2015) relating to non-indigenous macroorganisms used in biological control.

There are several categories of auxiliary macroorganisms:

• predators that devour their prey externally (e.g., ladybugs)
• parasitoids that use their hosts for part of their development. Endoparasites feed on their prey internally (e.g., Trichogramme), exoparasites externally.
• Entomopathogenic or molluscicidal nematodes are small worms that penetrate their hosts and release their symbiotic bacteria, leading to host death.

Macroorganisms are used in different control strategies:

• Control by acclimatization: introducing a natural enemy of the pest, taken from its original habitat.
• Control by augmentation: promoting the development of auxiliary populations short-term via inundative releases.
• Control by conservation: promoting the establishment of indigenous auxiliaries by maintaining biodiversity (hedges, shelters, shrub masses) to increase pressure on pests (intensification of biological regulation processes by habitat conservation). Conservation control is a foundation of agroecology.

Advantages

• Rapid action and durable control if conditions allow good establishment.
• Limits resistance phenomena linked to repeated applications of products from the same chemical family.
• Complements protection strategies and thus sustains certain molecules.
• Use of pollinators which improve the quality of vegetable and fruit productions.

Disadvantages

• High cost.
• Introduction must be early enough for effective pest control.
• Conditioning quality and transport conditions, if not optimal, can harm macroorganism survival.
• If prey is insufficient, macroorganisms may migrate or attack other useful auxiliaries.

Microorganisms

Microorganisms include viruses, bacteria, protozoa and fungi. Thanks to their diverse modes of action, microorganisms allow to act directly on bioaggressors or to stimulate plant defense capacity.

They have several modes of action:

• Parasitism: the microorganism specifically recognizes its target, penetrates its host and produces enzymes leading to its destruction.
• Antibiosis: the microorganism produces secondary metabolites toxic to the pathogen.
• Spatial and nutritional competition: prevents pathogenic microorganisms from establishing and developing.
• Stimulation of plant defenses

Microorganisms can be divided into two categories:

• those acting in direct interaction with pests.

For example, the commercial product POLYVERSUM containing the bacterium Pythium Oligandrum M1 attacks pathogenic fungi such as fusariosis of wheat or sclerotinia of rapeseed.

• those acting in indirect interaction with pests, notably Natural Defense Substances or Plant Defense Substances. These trigger the secretion by plants of molecules capable of inducing a cascade of reactions making them more resistant to diseases or pests.

Currently, about twenty microorganisms have been approved and are marketed for crop protection against certain diseases. Biocontrol products based on microorganisms are often used in integrated protection strategies in combination with chemical solutions.

Advantages

• Preserve auxiliaries and pollinators
• Preserve natural flora diversity
• Limit resistance phenomena

Disadvantages

• Persistence may be low
• Sometimes limited spectrum of action
• Possible toxicity
• Cost

Chemical mediators

Chemical mediators are volatile and soluble substances, produced by plants or animals in the environment and acting on the behavior and physiology of other organisms. These are extremely active substances acting in minute quantities and detectable over large distances up to several kilometers. In agriculture, chemical mediators are used for monitoring pest insect flights (capture devices) or for controlling insect populations (methods of sexual confusion and mass trapping). Two types of mediators are distinguished:

• Pheromones: chemical substances emitted by an individual of a species, which modify the behavior of another individual of the same species.
• Kairomones: chemical substances capable of triggering a particular behavior in an individual of another species that perceives them (favoring encounters between predators or parasites and their prey, promoting pollination or plant defense mechanisms…).

Advantages

• Very low toxicity for mammals and aquatic organisms
• No residues at harvest
• No toxicity for pollinators
• Very high specificity of action
• Durable protection method

Disadvantages

• Long implementation
• Renewal before the second flight
• Effective for at least 5 hectares
• Cost/time of work/efficiency: poor

Natural substances

They consist of substances naturally present in the environment and can be of plant (e.g., essential oils), animal (e.g., beeswax), mineral (e.g., sulfur, diatomaceous earth) or microbial origin. These natural substances have a direct action by ingestion or contact, or indirect by protective, repellent effect, or by stimulating natural plant defenses. There are herbicides (acetic or pelargonic acid), fungicides (orange essential oil, fenugreek extract …), anti-germinative (mint essential oil), nematicides (garlic extract), molluscicides.

Advantages

• Few residues in the environment after application
• Safe and low-risk products
• Reduced selection pressure on bioaggressors and resistance development to pesticides in pest populations
• Compatible with Integrated Organic Production programs

Disadvantages

• Slower, less active and persistent mode of action than traditional pesticides
• Need to repeat applications for optimal efficacy
• Sensitivity to unfavorable climatic conditions
• Need to know precisely the characteristics of the target pest

Choosing a biocontrol product

The choice of biocontrol product to use depends on various factors:

• current crop
• cultural specifications
• bioaggressor ...

Consult available biocontrol products according to the crop:

• Practicing biocontrol in viticulture
• Practicing biocontrol in market gardening
• Practicing biocontrol in arboriculture
• Practicing biocontrol in arable crops

Appendices

Est complémentaire des leviers

• Practicing biocontrol using natural substances
• Practicing biocontrol using sulfur
• Application of clay (calcined Kaolinite) in orchard
• Using sexual confusion in orchards and vineyards
• Practicing biocontrol in viticulture
• Practicing biocontrol in market gardening
• Practicing biocontrol in arboriculture
• Practicing biocontrol in arable crops

Défavorise les bioagresseurs suivants

• Slug
• Snail
• Weeds
• Wireworm
• Colorado potato beetle
• Powdery mildew of vine
• Leafrollers
• Whiteflies
• Botrytis cinerea
• Codling moth