Biocontrol agents are organisms, or material derived from nature, which are used to manage pest problems. These are often grouped into four main types, natural enemies (or invertebrate biocontrol agents), microbials (living organisms, metabolites or fragments of cell walls), semiochemicals (chemicals emitted by plants, animals or other organisms for intra- and/or inter-species communication, are target specific and non-toxic) and natural substances (materials which originate in nature or are identical if synthesised).
What are macrobials?
Macrobials, or Invertebrate biocontrol agents, are natural enemies including mites, insect predators, parasitioids and nematodes which control pests. Some examples are provided below:
Useful background information on some key pests and their management with macrobial biocontrol agents can be found in the Applied Bionomics Bio-control Handbook .
Amblyseius swirskii: The predatory mite A. swirskii is one of the most successful commercial natural enemies in covered crops. It is a generalist predator and is used commercially to control the major greenhouse pests; thrips, whiteflies and mites. More information regarding this natural enemy can be found in the BioProtection Portal Blog, “Top predator for protecting your covered crops: Amblyseius swirskii”.
A predatory mite Amblyseius swirskii attacking a food mite Carpophagus sp.
An example of a successful application of the A. swirskii can be illustrated with a case study from Spain, where it has been used to control pests in honey melon, https://www.ibmabiocontrolsuccess.org/ case /swirskii-predatory-mite- controls-pests-in-greenhouse-in-honey-melon-in-spain/ and also in aubergine production in Spain.
Watch the video below to see how the predator A. swirskii actively manages the whitefly pest in the glasshouse.
Nematoides, ou mais especificamente nematoides que matam insetos (entomopatogênicos) (NEPs), podem ser encontrados naturalmente no ambiente como parasitas de larvas de insetos. Nematóides de dois gêneros, Steinernema e Heterorhabditis, are used globally to control major insect pests within a range of different crop production systems. With the withdrawal of many insecticides due to their harmful effects on users and the environment, nematodes can offer an effective alternative to controlling these insect pests. They are particularly useful in managing pests that are difficult to target such as white grub and cutworm larvae which are found in the soil.
Os nematóides são uma ferramenta útil para o manejo de insectos pragas, pois eles;
- Pode ser usado sob condições de campo, cultivos sob coberta e em pomares, bem como grama
There are many commercial examples of the use of EPNs: in field crops to control soil-dwelling insect larvae of Cutworms (Agrotis spp.), em plantações de estufa para controlar larvas de mosquitos de fungo (Bradysia spp.), in fruit orchards to control Codling moth (Cydia pomonella) e larvas brancas (incluindo besouro japonês, Popillia japonica) da grama.
- Pode ser aplicado em substratos sólidos (solo, composto, etc.) ou na parte aérea (folhagem ou caules)
- Pode pesquisar ativamente a praga alvo, dependendo da espécie
For example, Steinernema carpocapsae utilizes an “ambush” strategy, waiting near the soil surface for target hosts, whilst Heterorhabditis bacteriophora has a “cruiser” strategy, seeking out its target.
- Atacam hospedeiros específicos
NEPs são parasitas de insetos e sua gama de alvos pode variar: S. feltiae, for example, attacking Coleoptera, Diptera, Lepidoptera and Hymenoptera whilst in contrast H. bacteriophthora only attacks Coleoptera, mainly Scarabidae. To see how the nematodes interact in a living system
- É improvável que promovam resistência nos insetos hospedeiros.
The EPNs themselves will not kill a host insect; this requires the EPNs symbiotic bacteria. When an EPN enters a host insect larva they release their symbiotic bacteria which kill the insect host. The bacterial enzymes then digest the larva and the EPNs feed on the products. To see an animated explanation of the mode of action
- São considerados seguros pelas autoridades nacionais, para o meio ambiente, usuários e consumidores
Demonstrou-se que os NEPs e suas bactérias simbióticas associadas não têm efeitos nocivos para os humanos ou outros vertebrados. Qualquer efeito não direcionado nas populações de invertebrados no campo é considerado de curta duração.
- Não se alimenta de tecido vegetal
Os NEPs não estão relacionados a nematóides parasitas de plantas e não utilizam o tecido vegetal como fonte de alimento.
- Do not produce any residue in crops
- Reduzem a necessidade de aplicação de pesticidas químicos.
- Podem ser aplicados utilizando sistemas de aspersão ou irrigação existentes.
Ao usar equipamento de pulverização convencional ou de pivô central, é necessário remover os filtros e peneiras e que os bicos tenham pelo menos 0,5mm de diâmetro e usar baixa pressão para evitar danos aos NEPs.
- Pode ser usado com outros agentes de controle biológico ou componentes de manejo integrado de pragas (MIP)
EPNs can be applied together with other biologicals such as Bacillus thuringiensis (Bt) or conventional insecticides such as Imidacloprid to manage insect pests, often with synergistic effects or the effective use of lower doses of insecticides.
- Pode ser usado na agricultura orgânica
Um exemplo de sucesso do uso de nematóides benéficos no Reino Unido é o controle do gorgulho da videira (Otiorynchus sulcatus) em morangos https://www.ibmabiocontrolsuccess.org/ case/beneficial-nematodes-epn-control-vine-weevil-in-strawberry-in-uk/
For a novel Claymation presentation of the entomopathogenic nematodes watch the video below.
What are microbials?
Microbials are micro-organisms, including bacteria, fungi and viruses and may also include their metabolites or fragments of cells.
Examples of fungal biocontrol agents
Trichoderma: A biopesticide with multiple modes of action and more besides
Trichoderma is a fungal group which contains a wealth of species used as commercial biopesticides. It is one of the most commonly used microbial biopesticides, with nearly 200 commercial products in the Americas, Europe, Asia and Africa. However, its use is much greater than the commercial sector with many local informal production facilities producing Trichoderma at a farm or community level.
Why is Trichoderma so successful?
A direct approach
Trichoderma spp. are primarily recognized for their direct biocontrol action against a wide range of pathogens, both soilborne and those on the aerial parts of crop plants. These pathogens include fungal and oomycete pathogens, such as Rhizoctonia, Fusarium, Verticillium, Pythium and Phytophthora. Although Trichoderma usually attack a wide range of pathogens, there are also those which have evolved to target a particular pathogen, such as T. stromaticum, which is effective against the witches’ broom pathogen in Brazilian cocoa orchards. These direct actions include;
Mycoparasitism; where the fungus colonizes and feeds on the mycelium of the host fungus
Antibiosis; where its metabolites directly act against the target pathogen
Competitive exclusion; where the physical presence of the Trichoderma actively prevents access to a host plant.
An indirect approach
In addition to these direct methods of antagonism towards a pathogen or group of pathogens, Trichoderma has other more subtle means by which it can aid a crop in combating pathogen attack. Close association of the Trichoderma within the rhizosphere, around the roots or within the roots, or even as an endophyte within other aerial tissues of the plant, can have a profound effect on the host plant. This includes;
- Increasing the solubilization and uptake of nutrients, thus improving the general health and fitness of the crop
- Activating the host plant’s defence system, priming it for a more effective response to the presence of a pathogen; analogous to human vaccination and subsequent immune response! This maybe local – or systemic – (throughout the host plant) induced resistance.
- Providing tolerance to abiotic stress such as drought, which in turn will provide resilience to a pathogen attack.
The extent to which these more subtle effects are expressed may be highly dependent on the Trichoderma spp. or strain selection for a given cropTrichoderma spp. colonising, and sporulating on, mycelium of Moniliophthora roreri (frosty pod rot pathogen) on a cacao pod
Where can Trichoderma be used?
Trichoderma can be used for crop protection in a wide range of production systems. It can be effectively used, dependant on manufacturers’ recommendations and national registration for;
- Covered crops, greenhouse or polytunnels
- Field crops
- Orchard crops
It can also be used in forestry, in nurseries for seedling production, but can also be used to manage the more rapid destruction of inoculum such as Armillaria spp. (in tree crops) and also Ganoderma spp. (in Oil Palm) by application to diseased material in the field.
Want to find out more about Trichoderma and its role in crop protection?
See how Trichoderma has been successfully applied in Spain for lettuce production in the field
Examples of bacterial bioprotection agents
Examples of virus bioprotection agents
What are semiochemicals?
Semiochemicals are chemicals emitted by organisms which act inter- or intra-specifically as a means of communication. They can act as attractants or repellants and have a specific, non-toxic mode of action.
Examples of semiochemicals
3.1.4 Natural Substances
What are natural substances?