Early results of Grains Research and Development Corporation and NSW Department of Primary Industries research shows delayed sowing may not be a useful tool for the management of crown rot.
Dr Steven Simpfendorfer, NSW Department of Primary Industries (NSW DPI) plant pathologist, says planting a variety early in its sowing window has the largest impact on final crop yield, followed by variety choice.
"Both of these factors far outweighed the crown rot effect so sowing a longer season variety does not seem to expose it to greater infection from crown rot, nor does delayed sowing impact on level of plants that get infected," Dr Simpfendorfer says.
"However, delayed sowing does increase the severity of crown rot infection as measured by the extent of basal browning.
"Decisions on planting date should be made on earliest adequate soil moisture levels and appropriate variety maturity used to manage frost risk in your region."
Dr Simpfendorfer said the percentage yield loss to crown rot in three bread wheat varieties was similar across three sowing dates.
He says later sowing decreases yield potential and grain size and increases screenings so adding crown rot into the picture further exacerbates losses.
"Last year was conducive to crown rot infection but the percentage yield and quality losses attributable to crown rot were pretty consistent across the three sowing dates," he said.
"If anything they got slightly worse with the later sowings so sowing earlier in the window, if soil moisture allows, maximises the genetic yield potential, grain size and limits screenings in a variety.
"This buffers detrimental effects from crown rot infection."
The research was a collaboration of NSW DPI and the GRDC-funded Northern Grower Alliance (NGA).
Richard Daniel, NGA chief executive officer, says the work was conducted in 2008 to examine the impact of sowing time and variety maturity on crown rot severity and yield loss.
"However it is important to note we are not talking about very early sowings in February to March," Mr Daniel said.
"The time difference between the first and third sowing dates was just over a month, from May 21 to June 27."
He said the researchers originally expected that early planting may increase the amount of disease infection and consequently yield impact but the results indicated that the delayed sowing actually increased the level of crown rot risk.
"This is work that will be repeated in 2009 as it may provide an additional tool to assist in practical crown rot management," he said.
The results suggest the earlier sowings benefitted from cooler conditions during grain-filling which appeared more important than the additional length of exposure to the disease.
"If this effect can be shown to be consistent, bringing grain-fill forward even one to two weeks may have a considerable impact on disease expression by limiting moisture and evaporative stress.
"Certainly there was nothing to suggest growers should be discouraged from sowing a variety early in its planting window due to a perception that this may make crown rot worse."
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