Insects and Other Animals in Tropical Forests

Abstract

Insects that cause economic damage to tropical trees can be classified into various categories according to how they feed. Defoliators remove leaf material, reducing tree growth by reducing photosynthetic area, sap feeders remove phloem or xylem sap, competing with the tree for its own products, whilst borers tunnel into bark or timber killing tress by girdling or damaging timber by creating holes or introducing stains. Insect pest outbreaks can occur for a variety of reasons. Primary pests such as sap feeders and defoliators may render trees susceptible to secondary pests such as the borers. In many cases, trees are susceptible to insect damage by virtue of being planted in locations, soils, and climatic conditions which are unsuitable for them; stressed trees are very often more likely to suffer serious pest attacks than healthy ones. Resistant trees must be grown if possible in sites to which they are suited. In addition, insect population densities may rise to damaging levels because regulation by natural enemies is reduced or missing altogether due to trees being grown in exotic locations, to insects invading from other regions or forest activities such as the removal of native vegetation or the misuse of pesticides. Insect pest management should always in the first instance be thought of as a preventative measure, since pest control, once insects start to cause significant losses, is frequently difficult if not impossible on large plantation scales. Monitoring of pest populations followed by predictions of damage intensities must be used to determine pest management tactics.