Dry masks threat of septoria: Agronomist
Drier conditions have masked what’s shaping up to be a sizable disease problem for wheat growers, particularly on higher yielding varieties under short rotations.
AW Vater & Co Agronomist Zack Zweck said septoria was particularly worrying on the Yorke Peninsula, with potential for yield losses between 20 and 30 percent.
“We started to see a lot more septoria in 2016, when we had the wet spring, but it wasn’t that hard to find in 2017 or 2018 for that matter, when it was a lot drier,” he said.
“There’s a few agronomists who are thinking like me; Septoria is a storm that’s building and when we do get a good spring, it could really punish us.”
Zack was involved in a 2018 trial that compared popular foliar fungicides alongside ELATUS ACE®, which is soon expected in the market. Loaded with a group 7 active constituent, Benzovindiflupyr, and a DMI (group 3), ELATUS ACE will help with resistance management.
“It’s going to have a really good fit, it was certainly the best performer last year in field trials,” Zack said.
Few wheat varieties offer much in the way of genetic protection against Septoria tritici blotch, particularly higher yielding varieties, with resistance cases now noted across South Australia, Victoria and New South Wales. The pathogen survives season-to-season on wheat stubble, with back-to-back wheat particularly susceptible.
Varieties like Mace and Sceptre have unfortunately experienced some of the highest incidences of septoria. The very same varieties growers on the Yorke Peninsula favour.
“Land is quite pricey around here and you can’t blame growers for wanting to make a good return,” Zack said.
“What’s complicated things here is a trend toward earlier season planting to avoid heat stress at grain filling stage, to really maximise yields. The problem is that these earlier crops are suffering early infection, during the airborne phase, when plants are getting established.”
Zack encourages his growers to take a strategic approach to septoria.
“I do encourage them to grow different varieties and I urge them to get a preventative spray on early, before the disease sets in,” he said.
“Typically we have gone in with triazoles at growth stage 30 to 32, and a quality fungicide at the flag leaf stage, particularly AMISTAR XTRA. ELATUS ACE is definitely a quality product.”
Prevention is better than the cure but Zack sees there being a greater degree of flexibility with ELATUS ACE as compared to other products.
“From the trial work, we saw excellent results as early as GS 23,” he said.
“By keeping the disease out, we aren’t seeing that secondary infection climb the plant, it displayed quite a bit of residual activity.
“Equally, if septoria did get away in a crop that didn’t benefit from an early spray, ELATUS ACE could be used at the flag leaf stage to protect those higher leaves.”
In the past two seasons Zack said yield penalties of between 5 and 10 percent have been common.
“It’s been a disease that growers have been pretty lucky with,” Zack said.
“Those products growers have used to control rusts have been masking the issue, but these sprays haven’t achieved the control of septoria that’s been required.
“If growers are getting screenings at harvest, the crop has clearly suffered at grain-fill. Ruling out other causes like moisture or heat stress, there’s a good chance septoria is at fault, and that can see samples fall from grade one to grade two, with a significant price penalty.”