Grain businesses in medium-to-lower-rainfall regions affected by the stubble-borne disease Fusarium crown rot now have the option of planting milling oats to avoid the devastating yield losses experienced by other cereals.

Researchers estimate crown rot costs the Western Australian grains industry $167 million every year in lost wheat yields, limiting crop rotation options in areas with high infection levels.

Nationally, it is estimated crown rot costs wheat growers $406 million annually.

Researchers say the prevalence of crown rot is increasing because of the increased practice of stubble retention and no-till farming practices.

However, with new milling oat varieties recently released to suit the shorter seasons of the medium-to-lower-rainfall cropping zones, growers in these regions now have more confidence to add oats to their rotations.

Research by the WA Department of Primary Industries and Regional Development (DPIRD) has demonstrated a high level of tolerance in milling oats to crown rot compared to wheat, particularly to the F. pseudograminearum species most common in the lower-rainfall regions.

Low impact on oat yields

Data from a two-year trial has shown almost no impact on oat yields in infected plots.

Trials in 2016 and 2017 at Merredin (lower-rainfall zone), Northam and Pingelly (higher-rainfall zone) compared seven milling oat varieties - Carrolup, Bannister (PBA), Durack (PBA), Kojonup (PBA), Mitika (PBA), Williams (PBA) and Yallara (PBA) - with wheat varieties Mace (PBR) and Emu Rock (PBR).

While both Mace (PBR) and Emu Rock (PBR) wheat experienced up to 17 per cent yield losses in infected treatments in the four trials, there was a negligible (4 per cent average) yield impact on all seven oat varieties, across all trial locations.

DPIRD plant pathologist Dr Daniel Huberli believes the findings present a major opportunity to growers reliant on cereals, allowing rotations to be diversified beyond wheat and barley.

We are now seeing growers achieve significant success with the new shorter-season milling oat varieties and so we wanted to test how oats reacted to crown rot.

Dr Huberli says previous research under the GRDC-invested National Crown Rot program, which began in 2014, did not include oats, given crown rot yield losses are most prevalent in lower-rainfall regions and oats have not traditionally been grown in these regions.

"But we are now seeing growers achieve significant success with the new shorter-season milling oat varieties and so we wanted to test how oats reacted to crown rot," Dr Huberli says.

Dr Huberli says additional research, a DPIRD investment through the Boosting Grains Research & Development project, tested inoculum levels at the start of the 2016 season, comparing this data with the inoculum levels at the start of the 2017 season, after both the wheat and oats treatments.

"Unfortunately, while we have evidence that yields from these varieties of milling oats appear almost unaffected by the fungus, we did not see any reduction in inoculum levels in the soil," Dr Huberli says.

"This means oats are not a break crop for this disease and other strategies will need to be used to reduce inoculum levels for future seasons."

Economic analysis outcome

As part of the research, an economic analysis was undertaken to better understand the profitability of planting milling oats in these lower-rainfall regions when compared to wheat, in paddocks infected with crown rot.

Dr Huberli says oats can be profitable for growers in paddocks with high levels of crown rot in medium-to-lower-rainfall regions if prices are around $270 per tonne, given the high yield losses expected in a wheat crop from crown rot.

In higher-rainfall regions, milling oats can be profitable at $180/t.

While the trials did not consider oaten hay varieties, Dr Huberli says he hopes future research will investigate this further.

Separate trials in 2018 under the GRDC-invested National Crown Rot project compared yield loss to crown rot in wheat, barley and milling oats at early and later times of sowing.

Later sowing date yields better

Dr Huberli says these first-year results suggest the earlier-maturing wheat varieties of Emu Rock (PBR) and Scepter (PBR) are yielding better at the later sowing date of 28 May. These are the best-yielding varieties in crown rot inoculated treatments and this was not affected by sowing dates.

"The late start to the season in 2018 may have influenced these interactions and so further work needs to be done to validate these results," he says.

He says these 2018 trials confirmed there was no yield impact on milling oats in crown rot infected treatments.

More information: Dr Daniel Huberli, DPIRD, daniel.huberli@dpird.wa.gov.au , National Crown rot epidemiology and management program.