Fusarium Species Causing Pokkah Boeng and Their Effect on Eldana Saccharina Walker (lepidoptera: Pyralidae)

Pokkah boeng is a fungal disease that can cause serious yield losses in susceptible varieties. Pokkah boeng is caused by Fusarium, but there is some debate regarding the species involved. Previous research has revealed that some Fusarium species isolated from sugarcane could benefit the development of the stalk borer, Eldana saccharina, a serious pest of sugarcane in South Africa. The aim of this research was to isolate and identify the causal organism of pokkah boeng and to determine the effect of the isolates on the development of E. saccharina. Eight representative isolates were inoculated into pokkah boeng susceptible varieties N34 and N41. Typical pokkah boeng symptoms were evident after three weeks. Isolates inoculated into the pot trial and the isolates obtained from inoculated, symptomatic plants were identified as F. sacchari, F. proliferatum and F. andiyazi. The isolates were included in E. saccharina diet and olfactory choice assays. When compared to controls in the dietary inclusion assays, three isolates were considered to be antagonistic (two identified as F. andiyazi and one as F. proliferatum) to E. saccharina, with the mean mass of surviving larvae being significantly lower than the controls. In this study, no isolates resulted in significantly greater larval mass than the controls. Results from the olfactory choice assays suggested that all isolates were attractive to E. saccharina, with significantly more larvae feeding on inoculated maize kernels than the uninoculated controls.