THE EFFECT OF ORANGE RUST ON SUGARCANE YIELD IN BREEDING SELECTION TRIALS IN CENTRAL QUEENSLAND: 1999--2001

THE outbreak of orange rust in the central district of Queensland in 2000 caused much turmoil in the sugar industry due to low yields in susceptible commercial crops and the high percentage of the crop planted to a susceptible variety. Plant breeding trials offer a way to assess the impact of endemic diseases on yield, and results from analyses conducted using central Queensland trial data from 1999- 2001 highlight the effect the disease can have on sugarcane yield. Orange rust reduced yield substantially (tonnes of cane and tonnes of sugar per ha) in harvests from 1999-2001. The losses were as high as 38% in tonnes of cane in 2000 harvests in highly susceptible varieties. The analyses suggest the disease was present in Mackay previous to when it was first recognised in January 2000. The disease may significantly reduce sugarcane yields and there remains a need to ensure commercial varieties contain adequate disease resistance.