Biological Control of Tropical Weeds Using Arthropods: Eichhornia crassipes (Mart.) Solms–Laub. (Pontederiaceae)

Introduction Eichhornia crassipes (Mart.) Solms-Laub. (water hyacinth; Pontederiaceae), an erect free-floating herbaceous plant, is indigenous to tropical South America (Gopal, 1987), but has been spread throughout the world. In the absence of its original suite of natural enemies, and usually in nutrient-enriched waters, it quickly becomes invasive, and is now the most important aquatic weed worldwide (Center, 1994; Julien et al ., 1996). It colonizes still or slow moving waters, resulting in thick extensive mats, which impede water traffic, reduce water quality (Edwards and Musil, 1975), and alter social structures for human riparian communities, such as those living on the Sepik River of Papua New Guinea. Infestations continue to plague freshwater bodies, particularly in tropical Africa (Navarro and Phiri, 2000), India (Kathiresan, 2000), and China (Ding et al ., 2001), causing significant environmental, economic and social problems, particularly for communities reliant on water bodies for sustenance and survival (Fig. 11.1). Taxonomy Eichhornia crassipes is in the Pontederiaceae, a taxonomically problematic family, which has recently been included in the Commelinales (APG II, 2003; Strange et al ., 2004). Eight other genera occur in this family of predominantly neotropical, freshwater aquatics, and eight species in the genus Eichhornia (Cook, 1998), all of which originated in South America, except E. natans (P. Beauv.) which is native to tropical Africa (Gopal, 1987). Only E. crassipes is regarded as a pantropical aquatic weed. The common names of E. crassipes are “water hyacinth”, ‘waterhyacinth’ or “water-hyacinth.”