Types of pest control
Natural pest control
Already in the year 3000 a. C. in Egypt, cats were used as a pest control method to protect grain stores against rodents. In 1939, a survey found that a cat population could drastically reduce the level of rats found in the area, yet they were unable to completely destroy the rodent population. However, if the rats were baited with poisons and the like, the cats could prevent them from returning to repopulate the area. (or at least an area of about 45 meters)
Biological pest control
Biological pest control is the control of rodents through the management of natural predators and parasites. For example: mosquitoes are often controlled by putting Bt Bacillus thuringiensis ssp. israelensis, a bacterium that infects and kills mosquito larvae, in local water sources. This treatment has no known side effects for humans or the rest of the environment, and it is perfectly fine to drink. The basic point of biological pest control is to completely eradicate a pest while inflicting very little damage to the surrounding ecosystem.
Mechanical pest control
Mechanical pest control is exactly what it sounds like, the use of practical techniques and the assistance of very basic equipment and devices. These protective devices create a barrier between plants and insects. One extremely simple thing about this is physically removing a weed from the ground. This is called tillage and it is one of the oldest methods of weed control known to man.
Destroying the breeding grounds
Proper waste management systems and disposal of standing water eliminate the risk of many pest infestations. This is a good example of why third world countries are often infested with disease-causing insects and rodents. Trash provides shelter for many unwanted pests and bacteria, as well as an area where still water can collect and create a breeding ground for mosquitoes. Again, this is why in first world countries you will see significantly fewer rats, cockroaches, mosquitoes, flies and other pests than if you were in a third world country. This is due to the poor garbage collection and disposal services provided in those countries.
Hunting
In the past, local communities in some European countries would get together when stray cats and dogs became numerous, gathering and killing all the animals where they did not seem to have an owner. Some countries even deploy rat catcher teams in which they chase rats out of a field where they are killed with dogs and simple hand tools.