The effect of damaging pests and diseases on forest plantations, worldwide, is reviewed. The basic ecological concept of diversity leading toward stability in ecosystems would lead to the conclusion that mixed species, natural forests are less susceptible to pests and disease than single species plantations. However, both natural forests and plantations are known to be adversely affected by these agents. Case histories of pest occurrence in both exotic and indigenous species plantations are given as well as case histories of introduced vs. indigenous pests. The most frequently encountered situation is when plantations of exotic tree species are attacked by accidentally introduced pests or disease.
Both natural and plantation forests should be managed with the objective of keeping them in a healthy, productive condition, one in which pests and disease are kept at low levels and do not interfere with management objectives. Integrated pest management provides a framework of decision-making and action tools designed to maintain and improve forest health.