Question

This is not an example of performing biological control of diseases/ pests using microbes.
(a) Trichoderma sp. Against some plant pathogens
(b) Nucleopolyhedrovirus against insects and other arthropods
(c) Ladybird beetle against aphids
(d) Bt-cotton to increase yield

Answer 1

Hint:
Biocontrol is the control of pests, diseases, and weeds of crop plants using biological agents. By using insecticides and pesticides i.e., chemicals are used to control pests. These chemicals are toxic and extremely harmful.

Complete step by step answer:
Trichoderma species are free-living fungi that are very common in root ecosystems. For plant pathogens, these have been proven effective. These species are developed to treat plant diseases caused by Trichoderma.
The majority of baculovirus used as biological control agents are in the genus Nucleopolyhedralvirus. This baculovirus attacks insects and arthropods.
The ladybird:- it is the beetle with red, and black markings and dragonflies are used to make free of aphids and mosquitoes respectively.
Hence the correct answer is Bt- cotton to increase yield.

Option ‘D’ is correct

Note:
Bt cotton is used to increase the yield as it is introduced to control butterfly caterpillars. This technique was developed by the use of genetic engineering. Different strains of bacterium Bacillus thuringenesis produce different toxins which are harmful to larvae of insects but not to other life forms. Generally, a gene encoding Bt toxin is inserted into cotton as a transgene. This makes cotton naturally resistant to its insect pest-bollworm (lepidoptera). The toxin crystals are produced by the cry gene. It is an endotoxin. These cry toxins are dissolved in the stomach of insects due to high pH levels. It forms ion channels which leave potassium movement unregulated. This leads to the death of the organism.