Bt Toxin and Biocontrol — NEET Biology
✅ Asked in NEET 2024The very familiar beetle with red and black markings – the Ladybird, and Dragonflies are useful to get rid of aphids and mosquitoes, respectively. An example of microbial biocontrol agents that can be introduced in order to control butterfly caterpillars is the bacteria Bacillus thuringiensis (often written as Bt). These are available in sachets as dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed. The bacterial disease will kill the caterpillars, but leave other insects unharmed. Because of the development of methods of genetic engineering in the last decade or so, the scientists have introduced B. thuringiensis toxin genes into plants. Such plants are resistant to attack by insect pests. Bt-cotton is one such example, which is being cultivated in some states of our country. You will learn more about this in chapter 10.
NTA tests how Bacillus thuringiensis (Bt) works as a biocontrol agent. The key concept: Bt produces toxins that kill insect larvae only when ingested—the toxin is activated in the larva's gut and is harmless to other organisms. Students often confuse this with how Bt toxin genes work in genetically modified plants; both kill pests but through the same toxin mechanism. Remember: Bt toxin is effective only against specific insect larvae that eat it, making it a selective pest control method. This explains why it's valuable for sustainable agriculture and why Bt-cotton is resistant to insect attacks—the plant itself produces the toxin.
This paragraph was tested 2 times in NEET.
Given below are two statements (NEET 2024) Statement I: Bacterial infection by Bacillus thuringiensis can kill only caterpillar larvae. Statement II: B. thuringiensis cannot kill adult moths.
Select the correct group of biocontrol agents. (NEET 2019)
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
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