Many insects are pests. They eat many of the
food plants farmers grow and, not surprisingly, farmers try many
tricks to stop the insects.
are the latest human invention for killing pest insects (the '-icide'
bit of 'pesticide' means 'killer'). Pesticides are poisonous chemicals
which farmers spray on their crops. The poison kills the insects.
End of problem. Well not quite. The
pesticides don't just disappear. They stick around and poison
many other creatures (including humans - are thought to die every year because of pesticide
poisonings). 
Untold
numbers of innocent animals die too, but no-one bothers about
them. Pesticides also pollute water supplies and plants
that have been sprayed with them often contain small amounts when
people eat them. People who support genetic engineering (GE) claim
that if farmers use GE plants which make their own pesticides,
then farmers will need to spray less pesticide which will be better
for everyone.
Things to think about