Jack always had a clean shaven face, he thought it suited him.
But then, all of a sudden, big bushy beards became fashionable. All his friends were growing them and Jack thought, “Maybe I should grow a beard – even though I will retain a lot of water there after showering, at least the wind won’t cool my chin anymore.”
So Jack grows the beard.
He’s feeling good, feeling confident about himself. He’s also saving money on shaving cream.
But then the beard starts to get really itchy. “This beard is so itchy it’s driving me crazy!” Jack said. “That’s it! I’m shaving some of it off.”
Jack decides to shave only part of his beard away, and keep a moustache and goatee. He said this will keep the wind off his chin and some water there after showering – “It’s nice and cool in summer, after all,” he said.
Research agronomists Mike Ashworth and Leon Hodgson are also managing their stubble to reduce fungal infections.
They’ve found windrow burning of wheat stubble reduces the amount of disease in the field which leads to a reduction in primary disease infection, and is therefore another tactic for reducing the risk of fungicide resistance.
“When growers feel their fungicide control was poorer than usual, or there’s been an extra high disease load, we need to do something more to ensure that any resistant pathogens do not get a chance to infect the following crop,” Mike said.
“We’ve found that burning windrows creates the perfect conditions to kill the target fungal populations in the windrow.
“This is a good result, as burning just the windrow allows growers to continue to gain the wind and water erosion benefits of no-till farming, while knowing they are also reducing the size of the fungal pathogen population which infects the following crop next season.”
How fire destroys fungal pathogens in windrows
Leon and Mike have been working with the Liebe Group growers Keith and Boyd Carter on a paddock under Mace out in Wubin to find out if burning windrows can destroy pathogens captured within the windrow and reduce disease load for next season. The site had huge disease infections in 2015.
Using thermocouples, they first measured exactly how hot it gets within the windrow, and compared this with how hot it gets when burning standing stubble. Interestingly, the temperature and duration of heat within the windrow was a lot greater than expected:
Within windrows, temperatures greater than 200oC were maintained for over 2000 seconds. In contrast, a standing stubble burn could only maintain a temperature of over 200oC for approximately 40 seconds.
Back in the lab, they then worked out how much time and heat was required to kill a mixture of fungal pathogens on wheat stubble. This was done by treating infected wheat nodes at different temperatures and durations and using agar plates to observe fungal growth after treatment:
They then plotted this data:
From the lab work, they now know that 200°C for 40 seconds is enough to kill pathogens on wheat stubble.
“This shows burning standing stubble is right on the border of being effective, unlike windrow burning which is more than effective,” Leon said.
“If you burn standing stubble, it needs to be a hot burn to ensure it’s effective. A cool, slow burn is likely to leave infective stubble behind.”
“By combining the field work with the lab observations, we can now say that windrow burning will be highly effective in reducing any pathogens that are captured within the windrow, and is a strategy worth considering to reduce our reliance on fungicides.”
So, in a nutshell:
Cutting stubble at the right height
Burning windrows will reduce disease load, but what is the maximum cutting height that would ensure that this technique is as effective as possible?
The team are currently analysing pathogen levels on different heights of wheat, with results expected in the near future.
“Cutting low to intercept disease can be difficult with available machinery and can slow down harvest. A better understanding of optimal cutting height is important to maximise the efficacy of this technique,” Leon said.
How does this research fit in a no-till system?
Mike and Leon have successfully added windrow burning as another tool for the integrated disease management toolbox.
They believe that windrow burning could be used when growers have experienced a tough disease season, or following poorer fungicide control than usual. In this way any fungicide resistant pathogens present could be concentrated in the windrow and destroyed.
“At the end of the day, it all comes down to diversity,” Mike said.
“We know that overreliance on fungicides rapidly leads to resistance, so we need to adopt novel strategies to reduce the population size and kill fungicide-selected pathotypes.
“If we add diversity into our agronomic programs, then we can take the pressure off fungicides, and in turn increase the longevity of the few fungicide modes of action that we use in Australia.”
About Leon Hodgson and Mike Ashworth
Leon has had an extensive research career in the agricultural industry, from GM lupin and wheat double haploid plant breeding, to non-wetting soil amelioration and grapevine phenology. Leon joined CCDM in 2015 and has been involved in developing and refining novel non fungicide management techniques to reduce foliar pathogen primary inoculum load as part of an Integrated Disease Management approach.
Mike has been a research agronomist at the CCDM for almost two years, leading integrated disease management projects such as this stubble management project. Mike has now moved on to a research agronomist role at the Australian Herbicide Resistance Initiative (AHRI). Farewell Mike!