THE AUSTRALIAN SUGARCANE SMUT EPIDEMIC: EPIDEMIOLOGICAL CONSIDERATIONS AND PREDICTIONS FOR THE FINAL STAGES

A SMUT epidemic probably began in Australian east coast sugarcane production areas as early as 2003, but was recognised for the first time in 2006. There has been a very strong industry response to the disease with emphasis on developing management options, and a focus on highyielding resistant varieties. The rates of disease spread and within-crop escalation of the disease have been examined; this paper reports on epidemiological considerations for this major epidemic for the coming few years. Natural-spread trials in the Mackay area have shown that highly susceptible varieties are infested very quickly; infestation of some less susceptible varieties has been slower and this may reduce, in part, direct yield losses caused by the disease. Monitoring of disease levels in susceptible crops has highlighted that some susceptible varieties succumb very quickly to smut while others exhibit more limited infestations, at least initially. Yield loss estimates have been made for the Herbert and confirm that sugarcane smut can cause major losses; it also suggests very significant crop losses will occur in the 2010, 2011 and, perhaps, 2012 seasons. Predictions are for the epidemic to peak in the first-affected districts (Herbert, Mackay and Bundaberg) in 2010 and 2011 while the disease should become a relatively minor influence on commercial crop yields after 2012. Critical years for the industry are therefore likely to be 2010 and 2011.