Introduction

Chromolaena odorata (L.) King and Robinson (Asteraceae), formerly known as Eupatorium odoratum L., is a weedy pioneering shrub native to the Americas from southern USA to northern Argentina (Gautier, 1992). Chromolaena odorata has become one of the worst terrestrial invasive plants in the humid tropics and subtropics of the Old World over the past century (Holm et al., 1977; Gautier, 1992). From its original point of introduction as an ornamental plant in northeastern India in the mid nineteenth century, it has spread throughout Southeast Asia, into parts of Oceania (Muniappan and Marutani, 1988; McFadyen, 1989;Waterhouse, 1994a), and into West and Central Africa (Gautier, 1992; Prasad et al., 1996). A different form of C. odorata (see below), first recorded as naturalized in the 1940s (Hilliard, 1977), has invaded a large part of the subtropics of southern Africa (Goodall and Erasmus, 1996).

Individual C. odorata plants are easily controlled by chemical and/or mechanical means. However, as it is a weed mainly of the tropics and subtropics, many of the countries in which it is a problem do not have the resources to implement comprehensive control programs using conventional methods. Consequently, biological control has become an important management tool (Goodall and Erasmus, 1996; McFadyen, 1996a).