YIELD LOSSES CAUSED BY SUGARCANE SMUT IN SEVERAL CROPS IN QUEENSLAND

SUGARCANE SMUT is a major disease world-wide, a direct result of the ease with which it spreads and the devastating effects it can have on crop yield. Previous Australian studies have focussed on highlighting the speed of spread across districts, the escalation of the disease within crops of susceptible varieties and the development of resistant varieties. In research reported in this paper, the losses caused by smut in commercial crops were investigated. Disease severity was assessed in a commercial crop of Q157 in the Herbert district; plots were marked encompassing varying levels of disease severity. All stools within each plot were given a severity rating between 0 (no disease) and 4 (grassy growth). The average severity rating for each plot was calculated and related to the commercial yield obtained from the same plots. There was a very significant relationship between disease severity and yield. A predicted maximum loss (‘0’ vs ‘4’ severity rating in individual plots) was 62%. Average losses in that particular crop were estimated at 26%. Similar effects of smut on individual stool yields were also estimated in a Mackay-based natural spread trial. Smut yield effects are similar to the results reported from overseas, confirming the status of smut as a disease of major significance.