The pesticide paradox

“A poor farmer loses his crop and is advised to use pesticide. The next season, he sprays the crop with DDT killing the pests and improving the yield. A few seasons later, the pests become resistant to DDT and now he is advised to switch to a different pesticide ‘Malathion’. The yield improves but the story repeats again after a few seasons.
“The pest that you kill with a pesticide, makes the pest resistant to that pesticide”.

This is the story of pesticide paradox, wonderfully illustrated by Dr Boris Bezier in his classic book “Software Testing Techniques”.