NORTHERN region grain growers deciding whether to plant wheat or barley in paddocks with a medium to high risk of crown rot infection in 2017 should weigh up key factors, including time of sowing and variety choice to maximise profits.
Crown rot is caused predominantly by the fungus Fusarium pseudograminearum (Fp), and is a major disease of wheat and barley crops in northern NSW and southern Queensland, estimated to cost growers around $97 million annually.
At the Grains Research and Development Corporation (GRDC) Grains Research Update at Condamine earlier this month, findings from a research project, which compared the relative benefit of growing barley or wheat in the presence of crown rot infection, provided timely insights for growers and advisers.
Funded by GRDC, the research project collected data from 32 replicated field experiments conducted between 2009 and 2015, and was undertaken by Steven Simpfendorfer, Rick Graham and Guy McMullen from the NSW DPI, Tamworth.
The field experiments included the bread wheat variety EGA Gregory, a widely grown cultivar across the northern grain region, and the dominant malting barley variety Commander.
Senior NSW DPI plant pathologist Dr Steven Simpfendorfer, said the results showed that Commander barley, in most seasons, yielded better in the presence of crown rot infection due to its earlier maturity, relative to the bread wheat variety EGA Gregory.
“Crown rot expression is most prevalent in conditions where there is heat and moisture stress during flowering and grain filling. Barley’s earlier maturity provides an escape mechanism which reduces its exposure to stress during these critical stages,” Dr Simpfendorfer said.
Dr Simpfendorfer said in 62 per cent of trial comparisons, the barley variety Commander provided a significant yield benefit (average 1.04 tonne/ha) over the bread wheat variety EGA Gregory, when grown in the presence of crown rot infection.
“In 30pc of trial comparisons the effect of choosing Commander or EGA Gregory was neutral in the presence of crown rot infection,” Dr Simpfendorfer said.
“And in 8pc of trial comparisons, Commander resulted in a significant yield penalty (average 0.48t/ha) compared to growing EGA Gregory, likely due to stress occurring earlier in the season.
“However, the crown rot fungus does not care what time of year it is when the stress occurs. If there is limited stored soil moisture and relatively high temperatures at earlier growth stages then the crown rot fungus will still proliferate which can reduce biomass production and even kill plants.
“Importantly, barley will not reduce inoculum levels for subsequent crops as it does not have improved resistance to crown rot infection compared to bread wheat.
“It is critical that growers do not continue to confuse improved yield performance in the presence of infection with resistance when considering crown rot.”
Dr Simpfendorfer said barley is very susceptible to infection by crown rot fungus and if sown later in its planting window is more likely to be filling grain under increased stress which may lead to significant yield loss from crown rot.
“To some extent this may also be why the barley variety Oxford, which has a longer maturity, does not yield as well as other barley varieties in the presence of crown rot infection. The escape mechanism is lost through the delayed maturity,” he said.
While some barley varieties may provide a yield advantage over bread wheat in a given season, Dr Simpfendorfer said some of the newer bread wheat varieties have started to close the gap.
“Research conducted across 11 sites in 2013, 12 sites in 2014 and 12 sites in 2015 has highlighted that some of the more recently released bread wheat varieties produced higher yield in the presence of crown rot infection than EGA Gregory,” he said.
“Trial results from Tamworth in 2014 found that crown rot infection caused yield losses in the barley varieties ranging from 10pc in La Trobe, up to 29pc in Oxford. In the bread wheat varieties, yield loss ranged from 14pc in Spitfire up to 23pc in EGA Gregory.
“All of the newer wheat varieties were higher yielding than EGA Gregory in the presence of high levels of crown rot infection.
“Suntop (0.73 t/ha), Sunguard (0.74t/ha) and LRPB Spitfire (0.85t/ha) provided the greatest yield advantage over EGA Gregory. However, even the best bread wheat variety, LRPB Spitfire, was between 0.51 to 1.32t/ha lower yielding than all of the barley varieties, with the exception of Oxford.
“Trials at Garah showed the trends in varietal yield performance in the presence of crown rot were consistent with Tamworth.”
Dr Simpfendorfer said while crop and variety choice was important, they were not the sole solution to crown rot and should be viewed as just one element of an integrated management strategy to limit losses from the disease.