Question

(i) Why are microbes considered effective biocontrol agents in sustainable agriculture ?

(ii) Explain the role of the following as biocontrol agents naming the pests or diseases they help to control :

(1) A Bacterium

(2) A Fungus

(3) Virus

Hint:

Microbes are specific and leave no toxic residue. Examples: Bt for caterpillars, Trichoderma for plant fungal diseases, baculovirus for insects.

Answer 1

Step 1: Part (i): why microbes work as biocontrol agents:
Biocontrol means controlling pests with living organisms instead of chemicals.
Microbes act on a specific pest and leave useful organisms alone. They do not leave toxic residues in the soil or the crop.
They multiply by themselves and do not pollute the environment, so they suit sustainable farming.

Step 2: Part (ii)(1): a bacterium:
\( \textit{Bacillus thuringiensis} \) (Bt) is used. Its spores are sold in dried form and sprayed on plants.
The caterpillar eats the leaf and the toxin protein is released in its gut. The gut wall breaks and the larva dies.
It controls butterfly caterpillars such as cabbage budworms and corn borer.

Step 3: Part (ii)(2): a fungus:
\( \textit{Trichoderma} \) species live in the root zone and are free-living fungi.
They are effective against several plant pathogens, so they control root diseases of plants.

Step 4: Part (ii)(3): a virus:
Baculoviruses (genus \( \textit{Nucleopolyhedrovirus} \)) attack insects and other arthropods.
They are species-specific and narrow-spectrum, so they do not harm non-target insects.
They are used against insect pests in integrated pest management.

Final Answer:
(i) Specific, residue-free and eco-friendly. (ii) Bt controls caterpillars, Trichoderma controls fungal plant diseases, baculovirus controls insect pests.