6. Biological control

Bio predators, bio-pesticides, bio-repellents, and bio-fertilisers are used to control microorganisms, pests, and insects that cause damage to the crops.

By introducing large numbers of predators, the pests are destroyed or killed. Predators like Chrysopa spp. and Menochilus spp. are useful in controlling a wide variety of pests like aphids, whiteflies, cotton bollworms, leaf insects, etc.

 

 

Bio-pesticides are commercially available but difficult to formulate in field conditions. They are of different types based on their origin.

 

Fungal bio-pesticides:

 

Trichodermaviride is a fungus used as a biological pesticide. It controls diseases caused by fungi such as wilt, rusting of leaves, and root disease.

 

Bacterial bio-pesticide:

 

A culture of Bacillus thuringiensis bacteria effectively controls the pest Lepidoptera that attacks cotton, maize, tomatoes, and tobacco plants. Panchagavya and leaves decoction of some plants are also used as biopesticides.

Compound Azadiractin obtained from neem seeds serves as an insect-repellant. Neem leaves, also called as margosa leaves, are one of the earliest pesticides used by humans. The dried leaves repel the pests from stored grains.

Bio-fertilisers are organisms that bring about soil nutrient enrichment. Nitrogen-fixing microorganisms can convert free nitrogen (atmospheric nitrogen) into soluble nitrogenous compounds usable by the plants, thus making the soil fertile. The main sources of bio-fertilisers are cyanobacteria and a few fungi.

 

 

Although chemical fertilisers increase the production and yield of food, they degrade the natural environment and habitat. Free-living bacteria live freely in the soil and fix atmospheric nitrogen and make it available to the crops like cereals, millets, fruits, and vegetables.

Free-living cyanobacterium involves nitrogen fixation along with the photosynthetic process.