ABSTRACT
Since the mid 1970s, CSIRO Division of Soils in Australia has had an ongoing major research program on conservation tillage at sites selected to represent major cereal-growing areas of southern Australia. Considering the quantities and range of herbicides used and the crops and environments in which they are used, it is surprising that there are not more deleterious interactions between herbicides and root diseases in conservation tillage systems. R. Heitefus discussed induced morphological and physiological changes in host plants which may ultimately alter resistance and susceptibility to plant disease. The mechanism of increased disease caused by Rhizoctonia with changing tillage practices appears to depend on the cropping system and the aggressiveness of the cultivation. D. K. Roget and A. D. Rovira showed that the severity and carryover of cereal cyst nematode is less in direct-drilled wheat than when the soil is cultivated.
