THE value of fungicidal treatment of yellow spot in susceptible wheat has been questioned, with new research showing a maximum of $1.50 profit gained for every $1 spent.
The research was undertaken by the Grains Research and Development Council, and chief executive officer Richard Daniel said results from 2011 research on the EGA Gregory variety showed single applications of full registered rates of all fungicides evaluated reduced yellow spot severity by up to 50% on the top three leaves. However, he said yield benefits were relatively modest - a 6% mean benefit across all fungicide treatments at the highest pressure site and a high point of 11% benefit.
"The trials involved single or multiple applications of fungicide on EGA Gregory wheat crops predominantly at GS31-33 or GS39 timings," Mr Daniel said.
"Multiple fungicide applications did improve disease suppression to the tune of about 70% reduction on the top three leaves but at the rates tested, there were no clear or consistent differences in disease suppression between the fungicides evaluated."
Mr Daniel said single applications (close to GS39) would provide good levels of disease suppression but would need to be applied before significant levels of yellow spot infection had been established on the flag leaf.
Previous recommendations of "applying after flag leaf emergence, when yellow spot is already colonising leaves below the flag and the forecast is for frequent rain events" are supported by these trials, he said.
"Certainly these results contrast with the consistency and level of benefits we get from the same fungicides on diseases such as stripe rust in wheat".
Mr Daniel presented the research results into crop disease management at the recent GRDC Update at Goondiwindi.
For more information, visit grdc.com.au/updates.
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