To accurately match the biocontrol agents with the organisms they help to control:
i)Ladybird
ii)Dragonflies
iii)Bacillus thuringiensis

i-aphids
ii-mosquito
iii-butterfly caterpillars

The correct answer is Option (2) –

i-aphids
ii-mosquito
iii-butterfly caterpillars

Ladybirds and Dragonflies are beneficial insects that help control aphids and mosquitoes, respectively. To control butterfly caterpillars, microbial biocontrol agents like Bacillus thuringiensis (Bt) bacteria can be introduced. 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.