THE EFFECT OF SMUT RESISTANCE ON DISEASE INCIDENCE AND SEVERITY UNDER NATURAL SPREAD CONDITIONS

THE SUGARCANE SMUT epidemic has reached a peak in the production areas where the disease was first recorded : the Bundaberg, Mackay and Herbert districts. The effect of varietal resistance on the disease has been very clear and has enabled effective management to be implemented. Further assessments of the effect of varietal resistance were undertaken in several trials in 2011 to highlight the linkage between resistance, incidence and severity. The effect of irrigation was also examined in a variety trial planted in the Burdekin area. In each case, a few highly susceptible varieties showed high smut incidence and severity, while varieties rated resistant, intermediate and susceptible (but not highly susceptible) showed much lower smut levels. Generally there was a good correlation between resistance and incidence / severity; highly susceptible varieties (Q117, Q157, Q207A) were affected to a much greater extent than other slightly more resistant canes. There was no evidence of increased smut arising from drought stress as created through restricted irrigation. Irrigation experiments may not replicate the effect of varying climatic influences on smut spore dispersal/infection, as they alter only the soil environment and not atmospheric conditions. Further assessment of the irrigation trial should be undertaken to confirm the responses seen. Current smut management practices are continuing to provide effective disease control under field conditions.