DETERMINING STRATEGIES FOR THE BIOLOGICAL-CONTROL OF A SUGARCANE STALK BORER

The African stalk borer, Eldana saccharina, has become a serious pest to the sugar industry in southern Africa. Over the past decade the South African Sugar Association (SASA) has been investigating numerous indigenous and exotic parasitoids as a means of biologically controlling Eldana infestations in sugarcane. Laboratory results indicate Goniozus natalensis to be one of the most promising parasitoids for this purpose. To aid in analysing its efficacy a mathematical model was constructed. The model comprises a system of differential equations governing the populations in the various stages of the E. saccharina life cycle and their interaction with the parasitoid G. natalensis. Using the model, various management strategies relating to the release of parasitoids were simulated. Relationships between the reduction in crop damage and the magnitude and frequency of releases were obtained. It was also found that a change in farming practices could lead to a self-sustaining parasitoid population with a 60% reduction in crop damage.