YIELD LOSSES CAUSED BY LEAF DISEASES: 1999 AND 2003 SELECTION TRIAL ANALYSES

YELLOW SPOT and orange rust are two of the most important leaf diseases affecting the yield of commercial crops in Queensland. Yellow spot is of greatest severity in northern Queensland while orange rust occurs in all cane-growing districts in Queensland and New South Wales. In order to determine more about their current economic effects and variation in yield losses in years with differing climatic conditions, further research correlating varietal resistance in breeding selection trials with clonal yield was undertaken. The research suggested that orange rust and yellow spot caused lower yield losses than Pachymetra root rot and losses were variable. Orange rust caused the greatest losses in the first year (2000 harvest) it reached epidemic proportions, especially in the central district. Since that time, losses have been significantly less. Losses caused by yellow spot were variable, being significant in some trials in some years.