PACHYMETRA ROOT ROT SURVEY OF THE TULLY MILL AREA

THE first Pachymetra survey of the Tully mill area was undertaken in late 2004, to determine the severity of the disease in the area. Soil samples were collected from selected crops of Q120, Q158, and Q200A in the seven districts within the mill area, and were assayed for Pachymetra root rot. More than 80 crops were sampled. Spore counts undertaken on these samples suggested wide variation in disease levels between crops, varieties and districts. The highest disease levels were recorded in the El Arish, Feluga and Euramo districts, while the lowest levels were recorded in the Murray Upper area. The results hinted that rainfall and period under sugarcane monoculture may be two factors worth researching as factors leading to higher counts. Spore counts in individual crops ranged from zero to over 600 000 spores per kilogram. High counts were recorded in some crops of Q200A, and these suggest that the disease needs to be monitored in fields growing this variety. The average spore count for the Tully Mill area in 2004 was 41 000 spores per kilogram. This is less than found in recent surveys of the Mackay area, but higher than earlier surveys undertaken in mill areas such as Mossman and parts of the Bundaberg area. Farmers should be aware that one recommendation does not suit the whole district, and there remains a need to undertake Pachymetra assays in individual cropping situations. The estimated annual economic loss from Pachymetra in the Tully mill area was estimated at $914 000, based on 2004 crop yields and cane price.