Pest Control

There are various microbial insect diseases that occur naturally and can be used as biological pesticides. These microbes outbreaks and make the insect populations denser. The bacteria used for biological control infect insects through their digestive tracts and hence it becomes difficult to control insects with sucking mouth parts like aphids and scale insects, with bacterial biological control. The most widely applied species of bacteria is Bacillus thuringiensis that is used for biological control, with four sub-species for controlling Lepidopteran, Dipteran and Coleopteran insect pests. The Fungi are also used for biological control and fungi that cause disease in insects are called as entomopathogenic fungi that include fourteen species of entomophthoraceous fungi which attack aphids. The species in the genus Trichoderma are also used for managing some soilborne plant pathogens.

There are various plants that are used for regulating insect pests. By selecting a wide range of plants for the garden, helps in regulating pests in a various ways such as masking the crop plants from pests as per the proximity of the companion, serving as nursery plants that provide breeding grounds for beneficial insects and producing olfactory inhibitors and odours for confusing and deterring pests. Other ways of using plants is acting as trap plants by offering an alluring food for enticing pests away from the crops.

The plants can also provide an alternative habitat in a form of a hedgerow, or beetle bank or shelterbelt where beneficial insects can reproduce and live. There are nectar-rich plants that bloom for longer periods as many beneficial are parasitic or predatory as larvae however, nectivorous during the adult stage. A good example of it is the soldier beetle, found on flowers as an adult, but its larvae feed on aphids, beetles, caterpillars, and grasshopper eggs. The countries like Benin and Vietnam use the legume vine Mucuna pruriens as a biological control for problematic Imperata cylindrica grass. The Mucuna pruriens is not invasive outside its cultivated area.

The Augmentation of biological control comprises of the supplemental release of natural enemies. It involves the release of few natural enemies at a critical monsoon time called as inoculative release or release of millions of natural enemies called as inundative release. Moreover, to augment the natural enemies, the cropping system may be modified and this practice is frequently called as habitat manipulation. An example of inoculative release takes place in greenhouse production of many crops. The periodic release of the parasitoid, Encarsia formosa, is used for controlling greenhouse whitefly and the predaceous mite, Phytoseiulus persimilis, for the control of the two-spotted spider mite. Also, there is frequent release of Lady beetles, lacewings, or parasitoids from the genus Trichogramma in large numbers (inundative release).

The Habitat or environmental manipulation is a type of augmentation that involves changing the cropping system for enhancing the effectiveness of a natural enemy. There are many adult parasitoids and predators that got benefitted from sources of nectar. Also, there is protection offered by refuges like cover crops, hedgerows, and weedy borders. The provisioning of natural shelters in the form of flowerpots, wooden caskets, or boxes is an example of this type. For example, the natural predator Dermaptera is stimulated by hanging up turnaround flowerpots in gardens with straw or wood wool.

The provision of flowering borders and mixed plantings can enhance the diversity of habitats and also offer shelter and alternative food sources. They are incorporated conveniently into home gardens and small-scale commercial plantings, but they are difficult to house in large-scale crop production. Some examples of habitat manipulation comprises of growing flowering plants (pollen and nectar sources) near crops for attracting and maintaining populations of natural enemies. For example, the hover fly adults get attracted to umbelliferous plants in bloom. Thus, augmentation is the effective way of biological pest control.

The Biological control of pests is a method for controlling pests like mites, weeds, insects that depends on herbivory, predation, parasitism, or other natural mechanisms. It forms an important part of the integrated pest management (IPM) programs. The biological Control is defined as the decrease in the population of pest by natural enemies and involves an active human role. The natural enemies of insect pests are called as biological control agents and it includes pathogens, predators, and parasitoids. The biological control agents of plant diseases are referred as antagonists and it includes herbivores as well as plant pathogens.

The Predators are basically a free-living species that consumes a large number of preys throughout their lifetime. It includes lady beetles and lacewings. Parasitoids are those species whose immature stage develops within or on a single insect host that leads to killing of the host ultimately. A majority of them possess a very narrow host range and it includes many species of wasps and some flies. The pathogens are disease-causing organisms such as bacteria, fungi, and viruses. They kill or debilitate their host and are specific related to some insect groups. Three basic types of biological control strategies comprise of conservation, augmentation and classical biological control.

The conservation of natural enemies is the most readily available biological control practice to homeowners and gardeners. In all areas from the backyard garden to the commercial field, there is occurrence of Natural enemies. They are adapted to the target pest and to the environment. The conservation is not only simple, but also it is cost-effective in nature. For example, the aphid colonies comprise of Lacewings, hover fly larvae, lady beetles, and parasitized aphid mummies. After periods of high humidity, it is common to have fungus-infected adult flies. All these are naturally occurring biological controls that are susceptible to the same pesticides which are used for targeting their hosts. The simple conservation means the prevention of the accidental eradication of natural enemies.

The chemical methods of pest control are frequently used for controlling the pests. Broadly, it is possible to classify chemical pesticides into two groups as per their potency. The broad spectrum pesticides have the ability for eliminating or incapacitating a diverse array of species. The narrow spectrum ones kill only a small and specific group of species. The strengths of these pesticides are, ironically proves to be their biggest weaknesses. They destroy the pests, but are also harmful to friendly animals. They also lead to the extinction of butterflies, many bees, and other insects from the plant. Nowadays, the chemical pesticide manufacturers advise the user regarding the amount of poisons to be used. They also detail about the how and when they need to be used and handled.

In order to make the chemical pesticides environment friendly, there are various researches being conducted. In spite of their drawbacks, these pesticides played major role in ensuring food security and proves to be good option till an equally potent substitute comes in the market. Pests occur everywhere in form or other across the planet. It includes the insects, bacteria, viruses, rodents, birds, mites, snails, nematodes, and others. They have the potential for eradicating the entire economies and starve the people if they are allowed to propagate without any control.

In earlier days, the pesticides available from natural sources were widely used. With the advancement in technology and rapid growth of population, the need for food and raw materials from natural sources has immensely increased. Thus, it becomes necessary to include more areas under commercial agriculture. The chemical pesticides or synthetic pesticides have been used widely during this period as they remove pests from large areas quickly and the left overs also offer resistance for some time period. The chemical methods have acquired great popularity because they can be used to counter all kinds of pest infestations.