A BRIEF HISTORY OF DISEASE EPIDEMICS IN QUEENSLAND AND OF SOME ECONOMIC OUTCOMES

VARIETAL COMPOSITION and individual variety dominance within mill areas, regions and whole industries influences the outbreak of disease epidemics in Queensland. Disease epidemics that have affected part or the whole industry within the past 60 years are brown rust, eye spot, Fiji leaf gall, leaf scald, orange rust, Pachymetra root rot, smut and sugarcane mosaic. The rapid onset of orange rust in a cropping situation dominated by one variety resulted in the most widespread, severe disease occurrence and largest, single-year financial losses of any of the epidemics. There was a strong correlation with some of these diseases (brown rust, Fiji leaf gall, leaf scald, orange rust and Pachymetra root rot) between the percentage of an area planted to one variety and the occurrence of a major disease epidemic. Financial analyses are reported which consider the profitability of individual varieties within a district or region versus the relative costs incurred as a result of the disease epidemic (was it the right decision to allow that variety to dominate production). These analyses showed that the industry earned more from Q124 than would have been the case if a mix of other varieties had been grown prior to the year of the orange rust outbreak (2000).