Mechanical harvesting reduces sphacelia/sclerote levels of claviceps africana

Abstract

A study was undertaken in Queensland (Qld) and New South Wales (NSW), Australia, between 1999 and 2001 to quantify the reduction in sorghum ergot (C. africana) sphacelia/sclerotia during mechanical harvesting of eight sorghum (Sorghum bicolor) crops (crop 1, grower A, at Warwick (Qld) in 1999; crops 2 and 3, grower B, at Warwick in 2000 and 2001, respectively; crops 4 and 5, grower C, at Nobby (Qld) in 2000; crop 6, grower D, at Willowtree (NSW) in 2001; crop 7, grower E, at Kingaroy (Qld) in 2001; and crop 8, grower F, at Dalby (Qld) in 2001). There was considerable variation in the mean number and mass of sphacelia/sclerotia between crops before harvest and in the range of values within crops. This variation was also reflected in the 'after harvest' data. In six of the eight crops (crops 1, 3, 4, 5, 7 and 8), the mean numbers and % w/w of sphacelia/sclerotia after harvest were significantly less than the corresponding values before harvest. The after-harvest % w/w mean values for seven of the eight crops (crops 2-8) were less than the Australia stockfeed limit of <0.3%; however, in three of these (crops 3, 4 and 7), the upper value of the range was >0.3%. The reduction in sphacelia/sclerotia mass, as a result of mechanical harvesting, ranged from 44% (crop 4) to 76% (crop 1), and the reduction in numbers ranged from 0% (crop 2) to 80% (crop 5). Findings suggest that mechanical harvesting can significantly reduce the admixture levels of sphacelia/sclerotia in sorghum grain.