Arrange the following steps in the use of Bacillus thuringiensis (Bt) to control butterfly caterpillars in the correct sequence:
A. The spores are eaten by the insect larvae feeding on the plants.
B. Dried spores of the bacterium, bought in sachets, are mixed with water.
C. The toxin is released in the gut of the larvae and the larvae get killed.
D. The mixture is sprayed onto vulnerable plants such as brassicas and fruit trees.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → B, D, A, C
Bacillus thuringiensis (Bt) is a bacterium used to control butterfly caterpillars. It is sold as dried spores, and it works only after the caterpillars eat it.
B – The dried spores, available in sachets, are first mixed with water.
D – The mixture is sprayed onto vulnerable plants such as brassicas and fruit trees.
A – The insect larvae feeding on these plants eat the spores.
C – In the gut of the larvae the toxin is released, and the larvae get killed. Other insects are left unharmed.
The correct order is B, D, A, C.
NCERT Extract:
Microbes as Biocontrol Agents – “… 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.”