Published on 29/09/2023
“We’re starting to see a shift in Septoria sensitivity to existing chemistry so the industry needs to incorporate new modes of action into those programmes before full resistance develops, and good chemistry is lost,” says national marketing manager Glen Surgenor.
“SDHI’s (Group 7) have been a market standard for the past decade, and we can’t afford to break them.”
He’s referring to ongoing Foundation for Arable Research monitoring, supported by all major crop protection suppliers, which tracks the sensitivity of New Zealand Septoria strains to fungicides with different modes of action.
Most recent testing suggests small sensitivity shifts in the SDHI fungicides, although they currently remain effective.
FAR data identify the biggest sensitivity shifts are in DMI (Group 3) fungicides, including significant changes for epoxiconazole and prothioconazole.
Surgenor says the value of such monitoring lies in giving NZ growers early warning of what might be coming.
“Unlike in the United Kingdom, for example, where they no longer have access to some SDHI technology because of resistance, we have time to protect what we have. But to do so, we can’t just keep doing the same thing we’ve always done.”
Cue Questar, with its unique active ingredient Inatreq. This is the first member of a new class of cereal fungicides, the picolinamides (Group 21), which have a different target site to all other fungicides currently applied for Septoria control in wheat.
Questar is the first naturally derived fungicide brought to market by Corteva Agriscience; Inatreq is produced by fermentation of a naturally-occurring soil bacterium first discovered at Osaka University in Japan.
It’s been winning support since Corteva launched it three years ago, but should be strategically integrated into more programmes as a critical circuit breaker to protect existing chemistry, Surgenor says.
It has no cross resistance to existing fungicides in the wheat market, and is highly efficacious, making it invaluable for resistance management strategies.
It’s also flexible in terms of application timing – up to T3 – although most applications will be at T1 or T2 which are the most important fungicide timings for Septoria control. But again, it must also be used with care.
“We’re strongly recommending only one Questar application per season, which will help protect Questar from the development of resistance, and also make the most of this new MOA in slowing resistance to other fungicide groups,” Surgenor says.
“We very much want to be part of a responsible resistance management strategy for all fungicides for Septoria and other cereal disease control.
Maintaining the efficacy of current fungicides requires careful management, which includes using different modes of action like Questar, applying the correct rates at the right time and growing Septoria tolerant wheat.
Questar – key points:
• Innovative resistance management tool – different MOA against a new target site in Septoria.
• Natural origin – derived from a soil microbe.
• Residual protectant, and curative activity.
• Flexible application timing – up to T3.
• Advanced formulation technology– improved retention and redistribution across plant surface as well as local plant mobility.
• Favourable toxological profile – low mammalian toxicity, low persistence in the environment.
For more information, contact your Corteva Agriscience territory sales manager.