Microbes as bio-control agents:

Bio-control is the biological method for controlling plant diseases and pests.

• Earlier, this biological control of pests and diseases was done by using chemicals. But they were found to be hazardous:

1. They are toxic to both plants and animals.
2. They also pollute the environment and soil too.

• So, to overcome above situation organic farming came in scope that works to create a system where the
  insects (pests) are not eradicated, but instead are kept at manageable levels by a complex system of checks and balances within a living and suitable ecosystem.

 Bio-control methods are following:

• Ladybirds and dragonflies are used to get rid of aphids and mosquitoes.
• Bacteria Bacillus thuringiensis(BT) are used to control butterfly caterpillars. These are available in sachets as dried spores which are mixed with water and sprayed onto crops, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get
  killed. Now-a-days the scientists have introduced B. thuringiensis toxin genes into plants. Such plants are resistant to attack by insect pests.
• Fungus Trichoderma species are free-living fungi which act as an effective bio-control agent of several plant pathogens.
• Baculoviruses are pathogens that attack insects and other arthropods. Most of them belong to genus Nucleopolyhedrovirus. These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications because they do not harm non target species. So, it comes under integrated pest management (IPM) program