EFFECTS OF SORGHUM ERGOT ON GRAIN-SORGHUM PRODUCTION - A PRELIMINARY CLIMATIC ANALYSIS

Until 1996 the disease 'sorghum ergot' (Claviceps africana and Clavice ps sorghi) was unknown in Australia. Following an outbreak near Gatton , the disease was found throughout most of the sorghum-producing areas in Queensland within 4 weeks. A climatic risk analysis was conducted to assess the likely timing and frequencies of further outbreaks of th e disease across the main sorghum-producing regions of Australia. Base d on the information available, likely conditions that could lead to a disease outbreak were formulated and a computer program developed to interrogate an existing database of long-term, daily weather records. Case studies were conducted for 10 key sorghum-producing locations, ra nging from Narromine in central New South Wales to Mareeba in far Nort h Queensland and Kununurra in Western Australia. For grain sorghum pro duction, crops flowering in January and February are unlikely to be af fected, regardless of location. However, in up to 30% of years, late-s own grain sorghum crops and crops flowering before January could be af fected, depending on climatic conditions prior to and around anthesis. The frequency and timing of these events differed strongly temporally and spatially and appeared highest in high rainfall years and in regi ons with relatively cooler temperatures and more frequent autumn rains . Hybrid seed production (i.e. breeding programs) and forage sorghum p roduction are likely to be more affected due to their inherently low p ollen generation, again with strong regional variation. Further applic ations of the methodology, such as the development of an early warning system, based on phases of the Southern Oscillation Index, are discus sed.