Credit: Infonet Biovision / Wam K Dennler
Credit: Wam K Dennler
Natural Enemies are Farmers’ Friends.
The natural enemies of plant pests are considered as farmers’ friends. Various beneficial organisms that can help the farmer to keep pests (and some diseases) under control and prevent them from causing economic damage.
Areas of land which have not been cultivated or disturbed contain hundreds or thousands of species which tend to form a balance, with each of them depending on some of the others. Although large outbreaks of plant-eating pests do sometimes occur in natural systems, any one particular species is less likely to build up a large population if the organisms which feed on it are also present – in other words, its natural enemies.
Predators are one type of natural enemies which tend to keep the population of their prey in check. They catch and eat other insects and mites, including pest species. Parasitoids are another type of natural enemies. They lay eggs in or on other species of insect (called hosts) and the larval stage kills the host as it feeds on it and develops. The third major group of farmers’ friends is pathogens. These are fatal or debilitating diseases to arthropod pests and include fungi, nematodes, bacteria, viruses, and other microbes. Fungi, particularly Deuteromycetes, can infect pests externally under favourable conditions, but other pathogens must be ingested to be effective as control agents. Pathogens are very specific to their hosts. Pathogens can be used as biopesticides because they can be applied in similar ways to chemical interventions.
Credit: Wam K Dennler
Beneficial living organisms which reduce pests and diseases are usually present in any crop unless broad spectrum pesticides (which kill a wide range of arthropods) have been used.
These so-called natural enemies can be conserved by taking care with farming practices so that they are not killed or are actually encouraged. If numbers of such biocontrol agents are still not sufficient to keep pests at acceptable levels, it is possible to release additional beneficial organisms of the same type – a process known as augmentation or inundation.
Farmers who collect ladybird beetles in field margins and release them on their crop are practising augmentation. Alternatively if suitable types of beneficial organisms are not present in the crop, they can be introduced. Where introduction involves a local beneficial organism which has simply not yet reached a particular crop, this is known as inoculation.
If the introduced beneficial organism is from outside the area (typically from the country or area where the troublesome pest originated) and becomes established as the controlling factor for the pest in the new area, it is known as classical biological control. A new balance is created so that the pest becomes less important.