The most common reason people use pesticides is to eliminate or keep "pests" in check. However, often pesticides are not needed.
The most important thing to learn as a pesticide-free gardener, is that not everything that looks like a problem, is a problem. Many insects are beneficial to plants and serve as predators to would-be pests. A problem that appears to be the result of disease or fungus, could actually simply be a case of too much sun, or too little water. Before you react to what you think is a pest problem, do a little research! If you reach for a pesticide before correctly identifying that you have a pest, you could actually make the problem worse or create new problems - by killing or deterring beneficial species from the area.
The websites below will help you identify common pest problems in the garden, and also suggest alternative ways of dealing with them!