T0 can be make or break timing for disease14 February 2018
T0 can be a make or break timing for protecting winter wheat’s yield potential against disease, says ProCam’s Head of Crop Production, Nick Myers.
Shifts in yellow rust races, plus heightened difficulties controlling Septoria tritici once established, have brought added weight to the argument for T0 fungicides, says Nick Myers.
Typically applied at growth stage 30, around the third week to the end of March, T0 is about managing risk, he maintains.
“You are trying to future-proof the crop by tackling disease on leaf four, to delay its progress to the yield-building leaves that follow.
“Don’t rely on the weather to do this. Cold weather just slows down disease development. If infection is there, it will come back in suitable conditions. Last year, once rain arrived in May, people started to panic if their earlier disease prevention wasn’t up to scratch.”
Usually after a wet UK winter, Septoria tritici is the most widespread problem that needs targeting at T0, says Mr Myers.
“Ideally, you would protect leaf four before a spore even lands on it.”
However, T0 is also a prime opportunity to get on top of early yellow rust or mildew – both of which were already present in crops before Christmas this season, he notes.
“A lot of varieties appear to have good resistance to yellow rust, but that is adult plant resistance. Before stem extension, the majority are susceptible.
“If you are risk averse, T0 provides an opportunity to lay down early control in this period. You could do nothing, but with the shifts in yellow rust races we’ve seen recently, you may not know what you’re dealing with until the end of the season. By then it’s too late. There’s a greater argument for erring on the side of caution,” he suggests.
Pointing to ProCam trials from last season, Mr Myers says even in what was initially considered a low disease year, a robust fungicide programme of a T0, followed by SDHIs at T1 and T2, plus a T3 spray, still delivered an extra 2 t/ha over untreated.
“The latest full-year results from our farm benchmarking system, ProCam 4Cast, show that the top 25% of growers who achieved the highest winter wheat yields spent a bigger proportion of their crop protection investment on fungicides.
“You don’t have to spend excessively on disease control, but you do need to spend in the right ways and have a plan from the start.”
From a practical viewpoint, Mr Myers says crops should be monitored for disease from February onwards – particularly varieties with known susceptibility to yellow rust.
“Thicker, forward crops this year will provide a sheltered environment for diseases. But interestingly, later-drilled crops can carry a lot of mildew, as the soft growth they produce as they race to catch up on growth stages is prone to infection. This could be an issue this season where growers delayed drilling either for blackgrass reasons, or where waiting for moisture after the dry autumn.”
Fungicide-wise, Mr Myers says a multi-site treatment, such as chlorothalonil, is a ‘must do’ against Septoria at T0. Then, assess what else needs adding against other diseases, he adds.
“Adding suitable triazoles to chlorothalonil will also control rust. But nowadays they will be largely protectant against Septoria tritici, rather than being curative.
“You can use different triazoles to epoxiconazole and prothioconazole at T0 to spare these for later. Alternatively, if rust is the main issue and Septoria risk is lower, there’s an option of using a strobilurin + chlorothalonil combination to avoid using a T0 triazole altogether. Selecting an appropriate strobilurin can also provide early take-all activity, which is important in second wheat.
“Mildew will need a specific mildewicide. And don’t overlook stem base diseases, such as fusarium, and possibly eyespot, which may require adjustments to fungicide choices.
“The overall message with T0 is to begin with a plan tailored to individual fields, rather than just reacting to the season. If you start off on the right foot you can stay on top of disease. If not, you can be chasing it all season long.”
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Photo credit: KUHN Agricultural machinery