REDUCING POOR ROOT SYNDROME OF SUGARCANE IN AUSTRALIA BY MINIMUM-TILLAGE PLANTING IN PREVIOUS INTER-ROWS

Poor root syndrome (PRS). a major disease of sugarcane in Australia wa s reduced by the use of minimum-tillage planting techniques involving planting into the inter-row of the previous crop. Populations of patho gens and yields were compared with planting into the previous row and with conventional cultivation and planting. The density or oospores of Pachymetra chaunorhiza was always lower in the inter-row at planting. At one site, planting in the previous inter-raw gave 14% higher yield s than planting into the previous row in the Pachymetra root rot susce ptible cultivar Q90. The Pachymetra root rot resistant cultivar, Q138, yielded 6% more when planted in the inter-row compared with planting in the previous row. The density of oospores of P. chaunorhiza in the row was ten times higher than in the inter-row at this site. At two ot her sites the oospore density was relatively low in both the row and i nter-row and no difference in yield was found between the two planting positions. At a fourth site, high oospore densities were recorded in the row but the inter-row also had oospore densities above the thresho ld for maximum disease in susceptible cultivars. No yield difference w as measured between the planting positions at this site. There was no advantage from conventional cultivation at the two sites where this tr eatment was included.