The term "biological control or biological control" has been defined differently by various biologists.
In the worst known definition, biological control; has been referred to as “the use of predatory insects (predators) and parasitoids to control another organism”.
Professor Harry Scott Smith, known as the father of modern biological control, defined biological control as "the use of natural enemies (whether introduced or otherwise manipulated) to control insect pests".
Dr. Paul DeBach further developed Professor Smith's definition, stating that biological control is "the act of keeping the population density of another organism at a lower average with a parasite, predator, or pathogen". DeBach defined biological control as "the maintenance of an organism's population density within identifiable lower and upper limits under the influence of abiotic and/or biotic environmental factors", distinguishing it from natural control.
Dr. Robert van den Bosch defined biological control as "manipulation of pest control by humans with natural enemies" and called natural control "control without human intervention".
In the light of these definitions, we can simply define biological control as “the use of a population of one organism to reduce the population of another organism”.
Biological control can be used to regulate numerous types of organisms: insects, mites, spiders, snails, weeds, trees, fungi, algae.
biological control;
- Classical biological control
- Protection of natural enemies
- It can be examined under 3 headings as the reproduction of natural enemies.
If a different or new pest enters the country from a different country and the pest does not have a natural enemy in the country it enters, the pest reaches a high population after a while, causing economic damage to the crops. In such a case, in order to deal with this pest, natural enemies are imported from the country of origin and placed in the region where the pest is found. Because it is the oldest known biological method, it is called classical biological control.
These are the measures taken to protect and maintain the natural enemy populations residing in a particular region. For example, avoiding or reducing the use of pesticides in that area for the protection of natural enemies.
Natural enemies in nature can suppress 95% of the pests in the agricultural ecosystem. For this reason, natural enemies need to be protected in order to increase their effectiveness.
Measures taken to increase populations or beneficial effects of natural enemies.
If the natural enemies cannot reproduce in the area they are in and cannot move on to the next year, or if they are not in the population that can keep the existing pest under control, the struggle with the release of mass-produced natural enemies into the area where the pests are located is called multiplying the natural enemies.
In this method, entomopathogens (those that cause disease on insects) are mostly used. In today's world, many entomopathogens are produced and used commercially against harmful species.
Biological control, which is a very broad concept, can be used in pest control in many places.
Plant pests can be confined to natural enemies such as fungi, bacteria or arachnids. Biological control can also be used to combat insects and fungal diseases and damage from nematodes. There are a variety of organisms and crops that can be used to grow many different crops, such as cereal seeds, oilseeds, potatoes, maize, peanuts, and cotton.
In open growing areas covering large areas such as fields, replicative biological control is more difficult to use. Instead, we can implement bioprotection control and support natural enemies against naturally occurring pests in the environment.
Biological control works well in greenhouses. It is important to apply beneficial organisms quickly when a pest appears. Thus, it is easier for the beneficial organism to control the pest. Today, biological methods are used in greenhouses for many pests such as spider mites, aphids, thrips and flies.
You can create good conditions for natural enemies in greenhouses, and biological control is often an effective measure if established early.
Insects, mites, bacteria, fungi, viruses, nematodes, fish, birds, mammals, snails and slugs, protozoa etc. found naturally in nature. There are natural enemy species in almost every living group, and they are grouped under the names of parasitoids, predators, entomopathogens and antagonists.
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The term parasitoid was used to mean "parasite" in many entomological literature and especially in older literature. However, parasitoids kill the host by feeding on their hosts, while parasites also feed on their hosts but do not kill the host. The pre-adult stages of parasitoids feed on only one host, they do not leave the host they feed on, and they use that host as a living place at the same time.
Adults, on the other hand, are mobile and generally need honeyed matter, nectar and pollen to survive. However, the adults of some species also feed on their hosts and in this way they are effective on their hosts. Parasitoids are usually smaller than their hosts and parasitize a certain period of their host. Thus, they are grouped as eggs, larvae, and pupal parasitoids.
In some cases, the parasitoid lays its eggs in any stage of its host and emerges from the next stage as an adult. For example, when the egg is released into the larval stage of its host, parasitoid adults emerge in the pupal stage of the host. Such parasitoids are called larval-pupal parasitoids.
Parasitoids that attack a non-parasitoid host are usually called primary parasitoids, and those that attack other parasitoids are called hyperparasitoids. Presence of hyperparasitoids in the environment is generally undesirable in terms of biological control. Parasitoids usually attack only one host species or several related species. This has made parasitoids the most suitable agent to be used in biological control.
They constitute a group of agents that are most used in classical biological control and biological control programs that are propagated and released due to their easy production compared to predators and narrow host spectrum.
While there are innumerable many species in natural and agro ecosystems, approximately 78% of parasitoids are found only in Hymenoptera and some in Diptera, it is reported that predators are found in almost all orders of insects more or less.
Predators found in many insect orders are usually polyphagous. Very few are specialized in a particular hunt. Both pre-adult and adult stages of these are usually hunters.
Although it is not very common, the adults of some predators are not consumed with their prey, but with honeyed matter, nectar, pollen, water, etc. They feed on substances. Adult predators lay their eggs in the places where their prey is found, the hatched larvae begin to search for their prey and consume what they find voraciously by either chewing or stinging-sucking.
They usually attack smaller and weaker prey. However, when some predator species attack larger individuals, they first immobilize them with a venom and then begin to eat them. It is known that some bride beetle adults consume up to 100 aphids per day in their 1-2 month life.
Because they are polyphagous, predators constitute one of the most important natural enemy agents that can be used in biological control programs, especially in the form of protection and support. However, the fact that mass production is expensive and difficult, and that there are significant difficulties in determining the activities of those produced in artificial nutrient media, limit the use of predators in biological control programs by multiplying them.
In addition, the occurrence of cannibalism in some species and the feeding of some species with other non-harmful creatures constitute other negative aspects of predators.
Entomopathogens used in biological control against insects include bacteria, fungi, viruses, protozoa and nematodes. In some literature, protozoa and nematodes are studied in separate groups with their own names. However, very few of them are used in pest control.
Entomopathogens found naturally in nature attack, infect, and sometimes kill insects. Many entomopathogens have been mass-produced and marketed as "biological insecticide". One of the foremost among them is Bacillusthuringiensis and it is used successfully against many insect species. Entomopathogens are generally applied by mixing with standard spraying tools or irrigation water.
These commercially produced entomopathogens are generally species-specific, so they can be safely used in biological control. Unfortunately, these preparations constitute only 2-5% of the world pharmaceutical market. Studies on this subject are continuing rapidly and it has been revealed that many entomopathogenic species give promising results in biological control.
On the other hand, it should be tried to increase their efficiency by creating suitable microhabitats for entomopathogens found naturally in nature.