Harvest is upon us, and as we edge towards the finish line, crop diseases are becoming far less of a problem. But what a season for diseases it has been!
In this Spotlight story, we’re taking a moment to reflect on what happened across Australia, and what could have been done differently in hindsight, with reflections from agronomist Dan Taylor (WA), agronomist Sam Holmes (SA), agronomist Greg Toomey (VIC) and pathologist Steven Simpfendorfer (NSW).
Dan Taylor, DKT Rural Agencies, Central Wheatbelt WA
With harvest very close (if not happening already), Dan said the cereal crops were looking good in his region, despite the powdery mildew in wheat being a big problem for growers.
“I think we managed the powdery mildew fairly well as best we could. Once we were aware it was spreading throughout the region, most growers were quite proactive in having a look, and we did manage it to the best of our ability,” Dan said.
“I think there certainly has been some yield loss associated. Hard to say at this stage, but in cases where we had poor or no treatment applied upfront, there will be some yield loss, in the order of somewhere between 5 – 15%.”
Dan said he will definitely make some changes with his recommendations for 2023, particularly with upfront fungicide management of wheat powdery mildew.
“We were trying to be sustainable and move away from using flutriafol across the board, as we had done since the last time we had a massive mildew outbreak in 2015, but we clearly got caught out in some cases,” he said.
“So I think the message going into next year will be to use flutriafol in-furrow but we’ll be drumming home that you must follow up with an alternate mode of action and a fungicide timing of somewhere around full flag leaf emergence, or even early head emergence, so we can make sure we are rotating that fungicide mode of action and not further treading down that path of resistance.”
Sam Holmes, Central Ag Solutions, Yorke Peninsula SA
Sam said the season is looking good with overall above average expectations for most crops.
He said considering the amount of disease around, it was mostly managed well, but if he could do the season again, he would have looked at different variety choices and more fungicide upfront.
“To go back in time, I wish we’d had some different variety choices in for wheat. Just watching how those varieties of wheat that were VS (very susceptible) went – to get even to S (susceptible) or MS (moderately susceptible) is a really big step up, particularly with powdery mildew,” Sam said.
“Also in hindsight, I wish we’d done a bit more flutrifol at seeding time just to keep disease levels more under control, as this gives you a little bit more time on your management regime when you’ve got that in the program.
“Other than that, though, I’m probably giving us a tick considering the season that we’ve had.”
Greg Toomey, Nutrien Elmore, VIC
With some extreme rust pressure around his region, Greg said they’ve been able to take some of the pressure off with flutriafol, but they still had to apply two fungicides – something they’ve rarely ever done before.
“In general we’ve lost a bit of leaf area, but overall I think we’ve maintained the vast majority of our yield potential on most of our crops,” he said.
“We’re hoping our wheat has 6.5 – 8 t/ha on the dry, which is probably double the average, but we’ve sort of thrown the kitchen sink at them in many cases for fungicides and nitrogen.”
Greg said following a successful pre-emergent program, and few weeds in winter, they left a lot of the herbicide work to the end of August to coincide with fungicide programs, when the weather is usually better and trafficability is okay to carry out a late tidy up of weeds as well as fungicide applications.
“But that wasn’t the case this year, so maybe as a strategy we should do a third of our cereals earlier, say in late July, early August, so that we have paddocks that can be sprayed by air with a fungicide and the planes are happy to do that, rather than relying on ground application for all of our crops,” he said.
“But this is probably a 1 or 2 in 10-type experience and the rest of the time that system works quite well.”
Steven Simpfendorfer, cereals pathologist from the Tamworth Ag Institute, NSW DPI
Steven said this season has seen a lot of disease, one of the biggest he’s seen in his time, receiving a lot of phone calls for advice.
“This has been massive and just so much complication and angst with the different pathotypes of stripe rust kicking around, causing confusion with varieties that reacted differently this year to last year,” he said.
In certain situations where very susceptible varieties were used and fungicide timing was not right, Steven said there would be some dramatic yield penalties from disease.
“There was a crop where the grower just couldn’t get the plane on it for ten days, so it didn’t get its flag leaf spray. We estimate it probably cost about 40 – 60 per cent in yield loss just from a 10 day delay in a plane,” he said.
“That happens in very susceptible varieties, fungicide timing is critical. So I think with the wet conditions, the lack of being able to get ground rigs on a lot of country, and the logistics of being able to spray so much country with planes, there’s really a question of how much acreage of very susceptible varieties we can sustainably grow.
“And with a wet summer likely, means our stripe rust risk (because it needs that green bridge to survive) is likely going to be very high again.
“So I think we’ve really got to look at the use of flutriafol on starter fertiliser and be a lot more proactive with that early management, as adult plant resistance kicks in later so we really need to protect these crops early and take the pressure down.”
A final word from CCDM
CCDM Director Mark Gibberd said it was fantastic to hear the prospects of an average to above average season, however, as with most wet seasons, diseases have still had an impact.
“One of the interesting parts of all the comments, is the need to really get on to diseases as early as possible,” Mark said.
“Early disease control, whether that’s seed treatments or in-furrow treatments, then a follow up with a good rotation of chemistry, is absolutely key to try and avoid the development of fungicide resistance and to optimise the efficacy of the chemistries that go on later.
“As we get more resistant material, that’s going to become easier with time, but in the interim, those early chemical applications and then the follow ups at the right time, in particular with the right rotations, are absolutely critical for success.”
Liked this blog? Why not listen to the full interviews on the Crop Disease Podcast.