How can insects, rats, and other pests be eradicated and controlled?

You don't want to eradicate them. Insects are extremely important. They are food for lots of other animals. They also are important in helping polinate plants and there are many that are detritavores. If they were not here we would be up to our ears in waste and we would not have the food we need to survive.How can insects, rats, and other pests be eradicated and controlled?
They can not. We can take measures to reduce their effects on our existence, but it is impossible to eradicate them without seriously causing something else to go wrong. And the ';something'; is worse than the original problem. It is better to learn to live with the problem, reduce its effects, and take precautions to keep it from becoming a larger one.