Biological control is a method of plant disease management by inhibiting plant pathogens, improving plant immunity, and/or modifying the environment through the effects of beneficial microorganisms, compounds, or healthy cropping systems. The involvement of the use of beneficial microorganisms, such as specialized fungi or yeast or bacteria to attack and control the plant pathogens and the diseases they are causing. A wide variety of bacterial genera, including Agrobacterium, Alcaligenes, Arthrobacter, Bacillus, Enterobacter, Erwinia, Pseudomonas, Rhizobium, Serratia, Stenotrophomonas, Streptomyces, and Xanthomonas have been described to have plant disease protection activity against fungal and bacterial pathogens. Many biocontrol strains can protect the host plant by out-competing phytopathogens for nutrients. They help the plant also by colonizing niches in the rhizosphere and preventing pathogens from infecting the plant. Natural pest control methods include cutting, mulching, mowing, tillage, and organic soil coverage and barriers. This method also includes simply hand-packing insects or hand-pulling weeds. Some devices can also be used to protect crops from pests. It includes row covers, protective nets with varying mesh sizes according to the pests.

A wide variety of bacterial genera, including Agrobacterium, Alcaligenes, Arthrobacter, Bacillus, Enterobacter, Erwinia, Pseudomonas, Rhizobium, Serratia, Stenotrophomonas, Streptomyces, and Xanthomonas have been described to have plant disease protection activity against fungal and bacterial pathogens. Biological control is a method of plant disease management by inhibiting plant pathogens, improving plant immunity, and/or modifying the environment through the effects of beneficial microorganisms, compounds, or healthy cropping systems. Biological control, the use of living organisms to control pests. A natural enemy such as a parasite, predator, or disease organism is introduced into the environment of a pest or, if already present, is encouraged to multiply and become more effective in reducing the number of pest organisms. The use of biological control suppresses the pest populations, making them less damaging than they would be. They play an important role in limiting the densities of potential pest and include natural enemies such as predators, parasitoids, and pathogens. Biological control, often referred to as “biocontrol”, is a method of reducing or eliminating the impact or damage caused by a target pest or weed using a biocontrol agent, traditionally a predator, herbivore or pathogen.

• Biological methods can be used to control plant diseases by using natural enemies or microorganisms that are capable of inhibiting the growth of pathogens or reducing their virulence. This approach is known as biological control and can be an effective alternative to the use of chemical pesticides.
• Microorganisms play a critical role in biological control of plant diseases. They can be used to control plant pathogens directly or indirectly by enhancing the natural defenses of the plants. Some of the microorganisms that are commonly used in biological control of plant diseases include:

Trichoderma spp: These are soil-borne fungi that are capable of inhibiting the growth of many plant pathogens. They do so by secreting enzymes that break down the cell walls of the pathogens, or by producing antibiotics that kill the pathogens.

Bacillus spp: These are bacteria that are commonly found in soil. Some strains of Bacillus are known to produce antimicrobial compounds that inhibit the growth of plant pathogens.

Pseudomonas spp: These are bacteria that are commonly found in soil and on plant surfaces. Some strains of Pseudomonas are known to produce antibiotics that can inhibit the growth of plant pathogens.

Mycorrhizal fungi: These are fungi that form a symbiotic relationship with plant roots. They can enhance the plant's ability to absorb nutrients from the soil and also stimulate the plant's natural defense mechanisms.

• Biological control of plant diseases can be achieved by introducing these microorganisms into the soil or onto the plant surfaces. This can be done by applying microbial formulations or by using plant growth-promoting rhizobacteria (PGPR) that can colonize the plant roots and provide protection against pathogens. In some cases, the use of biocontrol agents may require a combination of several different microorganisms to achieve the desired effect.
• Overall, the use of biological methods for plant disease control can be an effective and sustainable alternative to the use of chemical pesticides.

Dear Ajeet Kumar thank you for your contribution to the discussion

Biological treatment methods use microorganisms, mostly bacteria, in the biochemical decomposition of wastewaters to stable end products. More microorganisms, or sludges, are formed, and a portion of the waste is converted to carbon dioxide, water, and other end products. A variety of chemicals are available that have been designed to control plant diseases by inhibiting the growth of or by killing the disease-causing pathogens. Chemicals used to control bacteria fungi , and nematodes may be applied to seeds, foliage, flowers, fruit, or soil. A wide variety of bacterial genera, including Agrobacterium, Alcaligenes, Arthrobacter, Bacillus, Enterobacter, Erwinia, Pseudomonas, Rhizobium, Serratia, Stenotrophomonas, Streptomyces, and Xanthomonas have been described to have plant disease protection activity against fungal and bacterial pathogens. Biological control is a method of plant disease management by inhibiting plant pathogens, improving plant immunity, and/or modifying the environment through the effects of beneficial microorganisms, compounds, or healthy cropping systems. So, microbial agents are highly specific against target pests so they facilitate the survival of beneficial insects in treated crops. This may be the main reason that microbial insecticides are being developed as biological control agents during the last three decades.A pathogen is defined as an organism causing disease to its host, with the severity of the disease symptoms referred to as virulence. Pathogens are taxonomically widely diverse and comprise viruses and bacteria as well as unicellular and multicellular eukaryotes. Microorganisms that cause disease are collectively called pathogens. Pathogens cause disease either by disrupting the bodies’ normal processes and/or stimulating the immune system to produce a defensive response, resulting in high fever, inflammation and other symptoms. Biological wastewater treatment method, also known as the conventional method, is a common and widely used method of treatment. It takes into account biodegradation bleaching by taking aid of several micro-organisms, fungi, bacteria, yeasts, and algae.