Management of an incursion of sugarcane smut in Australia

Sugarcane smut is caused by the fungus Ustilago scitaminea, which is primarily spread by wind-borne spores and infected sugarcane cuttings. It was identified as a high-risk exotic disease in a pest risk analysis conducted in 1997, and a contingency plan to deal with incursions was prepared in 1997. Sugarcane smut was reported for the first time in Australia in the Ord River Irrigation Area (ORIA) of Western Australia in July 1998. The disease spread quickly through the susceptible cultivars NCo310 and Q117 (30% of the crop) and eradication of the disease was not feasible. Quarantine regulations were enacted in Queensland and New South Wales to reduce the risk of spread by plant material or appliances. The ORIA cane growers cooperated by ploughing out heavily infested fields and had removed all susceptible cultivars by 2001. This has reduced the risk of wind-borne spread from the ORIA. Extensive surveys of over 44 000 ha in Queensland and New South Wales have failed to detect sugarcane smut. Australian cultivars are being screened for resistance to sugarcane smut in Indonesia and the ORIA, and 75% of the cultivars tested are susceptible to smut. Breeding for smut resistance has commenced and smut-resistant cultivars have been propagated in preparation for possible incursions. DNA fingerprinting of the smut isolates collected from Western Australia and Indonesia showed that the isolates were identical. Further screening of isolates from around the world showed little variation except in Thailand, Philippines and Taiwan where there was significant variation between isolates within this region and with isolates from all other countries.