Research provides hope in face of rising crown rot levels
The understanding of crown rot and the challenge it presents cereal growers and their advisors, is continuing to evolve, through research into its prevalence and how to control infections.
While the challenge is perhaps better understood in the eastern states Syngenta is bringing a seed treatment to market to control this yield-robbing cereal disease across Australia.
Random crop disease surveys conducted across New South Wales in 2019 and 2020 by NSW Department of Primary Industries, with co-investment from GRDC, show Fusarium crown rot is the dominant cereal disease in that state.
Nationally it costs the industry more than $400 million each year.
Steven Simpfendorfer is a senior cereal pathologist with NSW Department of Primary Industries, based at Tamworth, and a Fusarium specialist.
He said that agronomists and growers are now finding the disease is worse in non-traditional Fusarium crown rot areas, such as central and southern NSW, than originally thought.
In wheat crops near Forbes last year, across nine paddocks six were showing medium to high levels of Fusarium crown rot, with up to 82 per cent plant infection recorded.
Based on the level of basal browning, Dr Simpfendorfer estimates the yield loss in 2020 across those six infected paddocks at between 17-20 per cent.
In Western Australia, where there has been a rapid uptake of no-till cropping systems, yield losses to Fusarium crown rot are estimated to cost the industry about $115 million annually. Back in 1998 the estimated cost to industry in WA was just $7 million.
Left image: Tell-tale basal browning as a result of crown rot (left).
Right image: A treated versus untreated sample from the same 2019 trial, exhibiting white heads (right), confirmed as crown rot.
WA consultant David Cameron said when he started his agronomy career in the 1990s, Fusarium crown rot was an issue in the lower rainfall regions, however over the past decade he had noticed distribution spreading into medium rainfall zones.
“Crown rot has increased on the back of the increased intensity of cereal cropping. Livestock have left the system and the pasture area has declined. Also, the dry seasons have limited the area of broadleaf break crops being grown,” Mr Cameron said.
“Low levels of infection are costing (some growers) 5-10 per cent of their yield in those low rainfall areas when there is a cut off finish.
“But every now and then a more severe infection will cause up to 30 per cent loss.”
However, for many growers, it’s difficult to quantify the cost of the disease and distinguish whether yield losses are due to Fusarium crown rot or other seasonal impacts.
According to Mr Cameron, that grey area means taking hard line approaches to rotations can be met with resistance from some growers.
“There is some rotation with fallow and broadleaf crops where the seasons allow it, but in general many growers are trying to use short season varieties like Emu Rock and now Vixen,” he said.
“Modern machinery allows us to inter-row seed, but those are minor contributors and a lot is left to the season.
“We do lack effective options. People are trying to do what they can, but they are managing the problem rather than getting on top of it.”
Following massive cereal plantings across the east coast last year, to restore stubble cover off the back of drought, Dr Simpfendorfer said many growers had little choice but to follow up with another cereal crop in the rotation in 2021.
This is likely to cause Fusarium inoculum levels to rise. However, Dr Simpfendorfer said simply removing residue isn’t the answer.
“Conservation cropping has large system benefits but means that the stubble-borne pathogen which causes Fusarium crown rot is going to be in paddocks,” he said.
“What we push hard is not to despair – burning stubble and aggressive management strategies such as cultivation can potentially have worse impacts overall.”
Syngenta, a global leader in agricultural research and development, has observed the challenge this has presented in Australia.
While the expression of this disease is mostly observed during plant maturity, Syngenta turned its attention to the early establishment phase when infection ordinarily happens.
Syngenta Technical Services Lead for Seedcare™, Sean Roberts, has been part of a project team that has developed TYMIRIUM® technology for use as a seed treatment to achieve early and lasting protection against Fusarium.
“VICTRATO®, powered by TYMIRIUM® technology, controls crown rot and provides management of root lesion nematodes in wheat and barley,” Mr Roberts said.
“Compared to existing seed treatments, VICTRATO® outstrips them, with fewer whiteheads and reduced basal browning. Being a novel mode of action VICTRATO® is delivering consistently superior yield, from the roots up, across our trials to date.”
Syngenta Technical Services Lead for Seedcare™, Sean Roberts
VICTRATO® is not registered, Syngenta lodged an application for the registration of the seed treatment with the APVMA on July 31.
Dr Simpfendorfer has observed crown rot trials where cereals have been treated with TYMIRIUM® technology.
“Once the Syngenta product (VICTRATO®) comes online, it will be another tool in the box for the management of Fusarium crown rot,” he said.
“It will give growers more flexibility, so you don’t get those blowouts in Fusarium crown rot that we have seen in the past.
“It’s going to be a very handy additional option for growers but the key will be using it in realistic situations and incorporating it into an overall integrated approach to Fusarium crown rot management.”
Speak to your local Syngenta representative about seeing a VICTRATO® trial near you.
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