Biopesticides and biological controls are pest and disease controls for plant protection based on living organisms and naturally-sourced compounds.
They are categorised as microbials, semiochemicals, natural substances and macrobials.
- The microbials consist of bacteria, fungi, viruses and other microorganisms or their metabolites or cell fragments that have the capacity to kill pests or outcompete and prevent diseases.
- Semiochemicals are message-bearing compounds produced by an animals or plants that can be used to change and disrupt a pest’s normal behaviour.
- Natural substances obtained from plants, minerals and animals can have antimicrobial, insecticidal or pest repellent activity.
- And macrobials consist of insects, mites and beneficial nematodes that when released will parasitize and feed on pests.
All can be used to disrupt, deter or kill pests and diseases attacking plants
We use the IBMA definitions for bioprotection and bioprotection agents which you can find using this link IBMA Bioprotection definition
For an illustration of what is meant by biological control watch the short video What is biological control? From the EU BIOCOMES project.
1.2.1 Natural biological control
Natural biological control is an ecosystem service whereby pests are regulated by natural enemies without any human intervention. This could be the situation in unmanaged natural systems such as tropical forests, as compared to agricultural systems.
1.2.2 Conservation biological control
Conservation biological control seeks to actively protect and enhance the abundance or activity of naturally occurring natural enemies (and microbes) & pollinators, by providing:
- Alternative hosts
- Food (energy) sources
- Shelter and refuge habitat
- Appropriate microclimates
- This type of approach also aims to avoid negative effects on beneficials, most of all by pesticides.
An example is the installation of border crops (including hedgerows) in agricultural areas, containing pollen producing plants, nectar producing plants, plants which harbour alternative hosts for natural enemies (banker plants) these provide shelter, nectar, pollen and alternative hosts for natural enemies and pollinators.
1.2.3 Augmentative biological control
Augmentive biological control is the periodical release of large numbers of natural enemies (or microbes) in a specific area. This can be either inoculative or inundative.
A beneficial organism is able to perform well when the pest is seasonally present in damaging numbers, even though it is unable to persist in sizeable numbers the year round. The introduction of relatively small numbers of such species that are present in the ecosystem albeit at insufficient numbers has been termed inoculative periodic colonization.
In contrast, in inundative releases, large releases are made to effect short term control of a pest. Inundative releases simulate pesticide treatments, and the agent simply reduces, rather than regulates, the pest population. Examples are the mass production and release of Trichogramma spp against corn borer species. However, sometimes differences become less clear, as for instance Trichogramma will reproduce in the fields after release thus resembling to some degree inoculative releases. Also in sugarcane, cotton and vegetables, small, inoculative releases of Trichogramma early in the season have proved just as effective in controlling moth pests as regular, massive releases throughout the season.
1.2.4 Classical biological control
Classical biocontrol involves the introduction of a host specific natural enemy (or microbe) from the centre of origin or diversity of a pest organism to manage the pest. This is approach is usually used against invasive alien species which have moved from their centre of origin or diversity to a new area without their coevolved natural enemies.
The classical biocontrol approach has been successfully used for many weed and insect pests including the use of the rust, Maravalia cryptostegiae, to manage rubber-vine weed, Cryptostegia grandiflora in Australia and the control of the Pink Hibiscus mealybug Maconellicoccus hirsutus in the Caribbean, using the predatory beetle Cryptolaemus montrouzieri and the hymenoptern endoparasitoids Anagyrus kamali and Gyranusoides indica.
More information can be found in section 3 on `Types of biocontrol agents`