SDHI resistance is threatening to hamper the ability of those chemistries to effectively control septoria and growers are being advised to protect winter-sown wheat crops with an early application of a folpet-based fungicide.

That advice comes from Adama Agricultural Solutions, which used this year’s CropTec event to warn growers that unless adequate steps are taken to protect the current armoury of fungicides, the efficacy of these products will continue to diminish, with growers subsequently left with a limited choice of crop protection options.

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,” advised Andy Bailey, Adama’s 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.”

He also warned 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 warned. “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.”

He advised growers to use a three-way stack of SDHI, azole and multi-site chemistries. “But it is important to ensure that the multi-site chemistry doesn’t impact on triazole uptake," he pointed out.

"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,” he added.