Herbicides are chemical pesticides that are used to manage vegetation. Usually, herbicides are used to reduce the abundance of weedy plants, to release desired crop plants from the competition. It is the context of most herbicide use in agriculture, forestry, and lawn management. Sometimes herbicides are not used to protect crops, but to reduce the quantity or height of vegetation, for example, along highways and transmission corridors. The reliance on herbicides to achieve these ends has increased greatly in recent decades, and the practice of chemical weed control appears to have become an entrenched component of the modern technological culture of humans.