A model for water hyacinth biological control

Abstract

Water hyacinth is one of the most invasive aquatic plants in the world. As such, there have been numerous attempts to model and predict its growth. Some of these models incorporate the influence of temperature or nutrients as the two most important determinants of water hyacinth growth. Other models include the effect of biological control on the growth of the plant, but only one model integrates environmental factors (temperature) with the effect of biological control. In this study, I attempt to incorporate temperature, and biological control effects on the growth of water hyacinth into a single model. Temperature-dependent water hyacinth and stage-structured Neochetina weevil population models were constructed in STELLA 9.1.4 and compared against an empirical dataset for two water hyacinth infested sites in South Africa for a two-year period (2004-2006). Although these models may not simulate field water hyacinth populations accurately, they suggest that Neochetina weevils can reduce water hyacinth populations, to below the assumed carrying capacity (70 kg/m2). It appears that the effects of Neochetina larvae are vital in reducing water hyacinth populations, and need to be further explored in order to simulate water hyacinth/weevil systems accurately.