With SDHI resistance threatening to hamper the ability of these chemistries to effectively control Septoria, growers should protect winter-sown wheat crops with an early application of a folpet-based fungicide. That is the advice from Adama Agricultural Solutions.
Septoria resistance to SDHI fungicides has been well documented over the last 12 months, with growers and agronomists being warned that the efficacy of these products could become eroded.
“Growers need to be aware that unless they protect the ongoing efficacy of SDHI chemistries, they may reach a point when they can no longer rely on this technology to provide foolproof protection against Septoria,” advises Andy Bailey, Adama’s Cereals Fungicide Technical Specialist. “With no new modes of protection arriving in the short term, and increasing regulatory pressures threatening the restriction and/or removal of many active ingredients, we could be looking at a scarcity of effective crop protection products in future years.
“Growers therefore have a responsibility to protect and prolong the efficacy and lifespan of existing chemistries by utilising alternative modes of protection, namely multi-sites, to slow the rate of resistance.”
Mr Bailey also warns that growers need to reduce their reliance on azoles. “Azoles still provide some curative benefit, but they are no longer fully effective in this role,” he warns. “In fact, trials have shown that the preventative effect of azoles has reduced by 20% over the last 10 years, while their curative efficacy has fallen by a huge 60% or more.”
In order to limit the effects of disease resistance, Mr Bailey advises growers to use a three-way stack of SDHI, azole and multi-site chemistries. “Stacking chemicals is recognised as the most efficient and effective method of crop protection,” he explains. “But it is important to ensure that the multi-site chemistry doesn’t impact on triazole uptake. To get the best results, a multi-site active, such as folpet, should be applied prior to stem extension at T0 and again at T1 to protect the newly emerged leaf 3. If disease pressures remain high, folpet can also be applied at T2 to combat fresh and spreading infections.”
Folpet-based products such as Arizona (straight folpet at 500 g/l) and Manitoba (folpet at 375 g/l plus epoxiconazole at 50 g/l) provide three stages of biochemical protection and are therefore less susceptible to resistant mutations. “They are more robust and as such are vital to prolong the role of azoles and SDHIs,” Andy continues. “New research even indicates that using folpet-based products such as Arizona can counteract the effects of selection pressure thereby making subsequent Septoria infections more sensitive to epoxiconazole.
“Folpet also aids green leaf retention, particularly when applied at T1, with this translating to the potential for improved yield benefits when compared to crops treated with chlorothalonil.”
Products such as Arizona and Manitoba provide an effective anti-resistance effect for the control of Septoria and also give good protection against other key cereal diseases including Yellow Rust. “Using these products early in the season reduces selection pressure and gives broad spectrum, flexible disease control in cereal crops. They can be used as standalone products or as mix partners for straight SDHI’s to provide a full ‘belt and braces’ approach to cereal crop protection,” Mr Bailey concludes.