Good seasonal conditions can mask the effects of fusarium crown rot and rhizoctonia root rot but growers should not be complacent about these damaging soilborne diseases, according to a Western Australian researcher.
“When soil moisture and nutrition is adequate, cereal plants may be able to do quite well even in the presence of high inoculum levels,” said Department of Agriculture and Food WA (DAFWA) plant pathologist Daniel Hüberli, who conducts Grains Research and Development Corporation (GRDC) funded research into soilborne diseases.
“The danger is that growers might be unaware that high disease inoculum levels are present and the diseases might cause significant damage to cereal crops during a dry spring or in subsequent drier years.
“This scenario is particularly the case for crown rot and has occurred in WA.
Dr Hüberli said keeping disease inoculum levels at low levels was the most effective way to minimise crop losses from root and crown diseases and this could be achieved by thinking long-term and implementing management practices over more than one cropping season.
He said detailed information about management options for crown rot and rhizoctonia was available in GRDC Tips and Tactics publications.
“Rotating crops is the most important management option for these diseases and the DNA-based service PreDicta B® can be used before next year’s sowing to identify soilborne diseases so cropping programs can be adjusted if necessary,” Dr Hüberli said.
“For diagnosis of suspected crop disease during the current growing season, contact AGWEST Plant Laboratories.”
Dr Hüberli said symptoms of crown rot were usually not evident until the tillering or heading stage of crop development and the impact of the disease was worse during a dry finish.
“Major yield losses occur when crown rot inoculum levels are high and there is moisture and/or evaporative stress during grain filling,” he said.
“However, signs of rhizoctonia can become evident earlier in the season – at about four to six weeks after seeding – when areas of poor growth (not necessarily bare patches) can appear.”
The GRDC is funding DAFWA trials in Merredin and Wongan Hills to assess wheat and barley variety tolerance to crown rot and improved management strategies through its national project ‘National crown rot epidemiology and management’.
This project is led nationally by the NSW Department of Primary Industries (DPI) and coordinated by the department’s senior plant pathologist Steven Simpfendorfer.