INVITATION PAPER (C.P. ALEXANDER FUND): CLASSICAL BIOCONTROL OF WEEDS: ITS DEFINITION, SELECTION OF EFFECTIVE AGENTS, AND ADMINISTRATIVE–POLITICAL PROBLEMS

Abstract

AbstractDilemmas in weed biocontrol are wide ranging. Even the term biological control is confusing as meanings may be restricted to the use of parasites and predators or extend to the use of all non-chemical means of control. Another problem is that two-thirds of the agents released do not become numerous enough to inflict major damage to the weed population, although this statistic is misleading as it includes agents costing little in pre-release studies where failure is of little consequence and those costing about two scientist years each, or currently about $400,000. Many of the suggestions for improvement are costly and time consuming. Delay is unacceptable where agent release is seen by sponsors as a mark of progress in a program likely to require 20 years and funding is difficult. Analysis of previous biocontrol attempts for attributes of "success" have been disappointing, partly because there are a number of steps involved, each with its own attributes. This paper recognizes four graded "success" steps and discusses many agent selection methods.There are public demands for a change in emphasis from chemical to biological control; but in the absence of effective enabling legislation, the practice of biocontrol can be legally and politically hazardous; biocontrol should be carried out by a multidisciplinary team but it is usually assigned to a single scientist; it needs to branch in new directions to remain scientifically stimulating, but this increases the risk of failure. Possible solutions for these dilemmas are discussed.