The incidence, severity and yield loss caused by 41 pathogens were assessed from a survey of 18 wheat pathologists covering the wheat-growing areas of Australia. The survey provided data on the frequency of years that each pathogen developed to its maximum extent, the proportion of the crop then affected in each growing area, and the yield loss that resulted in the affected crops with and without current control measures. These data were combined with crop production and quality data to estimate the value of the losses aggregated to the Northern, Southern and Western production regions. Pathogens were estimated to cause a current average loss of $913 × 106/year or 19.5% of the average annual value of the wheat crop in the decade from 1998–99 to 2007–08. Nationally, the three most important pathogens were Pyrenophora tritici-repentis, Puccinia striiformis and Phaeosphaeria nodorum with current average annual losses of $212 × 106, $127 × 106 and $108 × 106, respectively. If current controls were not used, losses would be far higher with potential average annual losses from the three most important pathogens, P. striiformis, P. triticirepentis and Heterodera avenae, being $994 × 106, $676 × 106 and $572 × 106, respectively. The average value of control practices exceeded $100 × 106/year for 12 pathogens. Cultural methods (rotation, paddock preparation) were the only controls used for 10 pathogens and contributed more than 50% of the control for a further eight pathogens. Breeding and the use of resistant cultivars contributed more than 50% of control for seven pathogens and pesticides for three pathogens. The relative importance of pathogens varied between regions and zones.
bacteria crop loss assessment fungi nematodes rust Septoria tan spot viruses