Chapter 34 - Biological Control of Weeds in Terrestrial and Aquatic Environments

Abstract

Biological control is the study of relationships among weeds, their associated organisms, and the environment, followed by the manipulation of selected species of these organisms to the detriment of a target weed species. The natural enemies used in biological control are self-perpetuating only in the presence of their weed hosts and only within the limits set by the environment. Developing a biological control program begins with a systematic assessment of the weed problem that includes assuring proper identification of the target weed, charting the weed's geographic range, characterizing the habitats it infests, ascertaining the losses caused by the weed, determining the degree of control required, and compiling a list of natural enemies already present or reported elsewhere. Implementing biological control through conservation of natural enemies can be complicated. It requires a thorough understanding of the weed and environment relationship, as well as the technical ability to manipulate aspects of this relationship to increase agent impact. Biological control through the conservation of natural enemies relies on enhancing the buildup of populations already present and augmentation utilizes large-scale releases or applications of natural enemies collected or reared elsewhere.