Pests are organisms—such as insects, arachnids, rodents, and others—that cause harm to human health, food, property, or the environment.
The key to determining whether a species is a pest lies in whether it conflicts with human activities and causes actual damage.
For example, bees collecting nectar from flowers are beneficial, but when they build a nest inside a home, they become pests.
Similarly, termites breaking down dead wood in a forest are a vital part of the ecological cycle, yet when they bore into the wooden structures of a house, they pose a serious threat.
Out of roughly one million known insect species worldwide, fewer than 1% are classified as pests.
The definition of a pest is relative and context-dependent—the same organism can shift from beneficial to harmful in different situations.
Modern pest management emphasizes the concept of the "economic threshold": human intervention is warranted only when a pest population exceeds a certain density and the damage it causes outweighs the cost of control.
In a household setting, this typically means that spotting a single cockroach occasionally doesn't necessarily require a full-scale treatment, but if sightings become persistent or happen during the day, action is needed.