Why Things Bite Back: Unintended Consequences of Biological Weed Control

Abstract

There is an upside and a downside to the current “boom market” in biological control, the use of living organisms to control pests. The upside is that biological control provides a potentially effective control technique, an alternative to chemical pesticides, and an ecological foundation for pest control strategies. As a method of weed control, biological control can claim a growing number of successes. As of the end of 1996, there have been at least 1150 planned releases of 365 species of invertebrates and fungi on 133 weed species in 75 countries (Julien and Griffiths 1998). (1989) estimates that 25% of all releases made up until 1985 contributed to control; some recent estimates of success rates are higher (McFadyen 1998). As an alternative to chemical pesticides, biological control potentially reduces pesticide use and its undesirable effects on human health and the environment (OTA—U.S. Congress Office of Technology Assessment 1995). In contrast to chemicals, biological control organisms pose negligible human health risk, circumvent the problem of pest resistance (Holt and Hochberg 1997), and reduce the need for repeated and costly interventions to control invasive species, plants and animals that are not native to ecosystems they invade (OTA—U.S. Congress Office of Technology Assessment 1995). As an exercise in applied ecology, the scientific study of biological control systems has helped transform perspectives in pest control from an industrial to an ecological model (Levins 1986), fostering a sustainable pest control technology (Karban et al. 1997) that potentially (1) is effective, (2) requires low inputs of resources, (3) is self-perpetuating, (4) produces minimal pollution, (5) produces minimal effects on nontarget organisms, and (6) is compatible with other management practices.