A quantitative post-release evaluation of biological control of water lettuce, Pistia stratiotes L. (Araceae) by the weevil Neohydronomus affinis Hustache (Coleoptera: Curculionidae) at Cape Recife Nature Reserve, Eastern Cape Province, South Africa

[from the introduction] Water lettuce, Pistia stratiotes L. (Araceae) is recognized as being among the world’s worst aquatic weeds. In its adventive range, the plant forms extensive mats capable of blocking navigation channels, impeding water flow in irrigation and flood control canals, and disrupting hydropower generation (Holm et al. 1977). Dense mats of the weed prevent light penetration into the water column which negatively affects submerged aquatic plant communities, causing a lowering of the oxygen concentration and thereby reducing benthic invertebrate and fish populations (Neuenschwander et al. 2009)