(a) How do organic farmers control pests ? Give two examples.
(b) State the difference in their approach from that of conventional pest control methods.

(a) The organic farmers control pests by using the plants genetically modified for pest resistance. Usually, the gene that makes the plant resistant to the pest is introduced into the plant.

For Example -
i. Bt Cotton : The cotton plants were incorporated with the Bt toxin gene of the bacterium Bacillus thringiensis. The gene known as the cry gene provided the cotton crops resistance against the bollworms.

ii. The nematode Meloidogyne incognita infects the roots of tobacco plant and causes reduction in yield. RNA interference (RNA i) involve silencing of a specific RNA. Using agrobacterium vectors, Nematode specific gene is introduced into host plant. The introduction of DNA was such that it produced both sense and antisense RNA into the host cells. These two RNAs being complementary to each other formed a double-stranded RNA that initiated RNA interference reaction and provided protection against the pest.
(b) In conventional pest control, various pesticides were sprayed on the crops or agricultural fields to provide protection against the pests. This usually killed the good insects or organisms too and was responsible for pollution too. The pesticides used were toxic to animals and humans too. 
However, the organic farming does not involve the use of pesticides and hence caused less pollution and toxic in nature.