Natural population fluctuations may cause a temporary increase in a pest population, but these are usually brought under control by a corresponding increase in predator populations. The checks and balances that have evolved in the ecosystem over time provide stability and generally don't require any intervention on our part. In many cases a pest situation is complicated by the existence of a pest complex, a number of pests that act in various ways on a tree. When dealing with a pest complex, it makes sense to identify and control the primary pest or cause of the weakened trees. It can be a natural occurrence like climatic change, the introduction of a non-native organism, or any number of other circumstances.
Stress is often at the heart of a pest problem.
Healthy trees have natural defenses to injury and are much less likely to suffer from pest attack than those that are stressed. For this reason, the best strategy in dealing with pests is generally a proactive effort to keep your forest healthy. One of the most important stress-causing agents is drought. Others include excessive rain, competition from other trees, air pollution, soil problems such as compaction, excess pruning, insect damage, etc. Knowing how to maintain the health of your trees and minimize stress is an integral part of pest management.