Question

Write a note on biocontrol agents.

Answer 1

i. The agents which are employed for biological control are called biocontrol agents.

ii. Microbes like bacteria, fungi, viruses, and protozoans act as biocontrol agents. They act in three ways, either they cause the disease to the pest or compete or kill them.

Example:

i. Bacillus thuringiensis

1. It is used to get rid of the butterfly, caterpillars where dried spores of Bacillus thuringiensis are mixed with water and sprayed onto vulnerable plants such as Brassica and fruit trees.
2. These spores are then eaten by insect larvae.
3. In the gut of the larvae, the toxin (cry protein) is released and the larvae get killed eventually.

ii. Trichoderma

1. Trichoderma species are free-living fungi found in the root ecosystem (rhizosphere).
2. These are effective as biocontrol agents of several soil-borne fungal plant pathogens.
3. The fungus produces substances like viridin, gliotoxin, gliovirin, etc. that inhibit the other soil-borne pathogens attacking root, rhizomes, etc. causing rot disease.