Winter wheat crops face 'disease control'
Winter wheat growers planning important May T2 disease control decisions will have a number of new considerations this season, with buoyant grain prices and new fungicide chemistry to choose from, say industry experts.
Therefore, it will be important to take these into account, alongside disease risks and drought-affected crops, in order to achieve the best return on investment, they add.
According to Syngenta business analyst Mark Hall, T2 is the most critical fungicide spray of the season, because the uppermost flag leaf and second leaf, both of which are targets for the T2 spray, can contribute well over 60% to yield. Moreover, crops are in financially good shape with wheat prices around £170/t for November 2011, he adds.
"Grain prices are now amongst the highest they have ever been," says Mr Hall. "So there’s a significant amount of margin to be achieved by pushing crop yields.
"Even in an unusually low disease year, such as last year, T2 sprays were found to give a yield response of 0.5 t/ha. In a higher disease year the response was up to 2 t/ha."
Syngenta technical manager Chris Rowsell agrees and says with yellow rust, in particular, now reported in most parts of the country, and a large proportion of the UK wheat area susceptible to yellow rust, it will be important to take this into account in fungicide decisions – even if it isn’t immediately apparent, he adds.
"With the value of crops in the ground, you don’t want to risk their potential," says Mr Rowsell. "We know many growers will be trying the newly-launched SDHI fungicide Seguris for the first time this season – and that’s a good approach because it is broad-spectrum, and yellow rust is a particular strength.
"But where Seguris isn’t available then the traditional strobilurin approach of Amistar Opti tankmixed with a triazole such as epoxiconazole is still a good option. From independent trials it has been calculated to give more than £10/ha extra margin over an alternative strobilurin + triazole + chlorothalonil tank mix," he adds.
Bill Clark, director of Broom’s Barn Research Centre, agrees that yellow rust is widespread and that new SDHI fungicide chemistry at T2 has a clear place.
The starting point for fungicide decisions should be triazoles with chlorothalonil included for added Septoria control, he says, with either a strobilurin or an SDHI.
An SDHI fits because it can increase disease control, help protect triazoles from resistance, maintain green leaf area, and increase yield even where disease control is not improved, says Mr Clark. But in particular, he highlights evidence of improved drought tolerance from SDHI use, against a backdrop of 30% of UK wheat being grown on drought-prone land.
Testing at Broom’s Barn of the SDHI active ingredient in Seguris, IZM (isopyrazam), showed improved greening in drought conditions. Last year in the field, even in the absence of measurable disease, green leaf area on the top two leaves was increased from 59% in untreated to 95% following Seguris treatment, he points out.
"This has an effect in terms of grain-filling because you’re maintaining green leaf area," adds Mr Clark.
"All SDHIs – including IZM – have non-fungicidal activity. They have a number of physiological effects. It’s like with strobilurins – we were seeing yields above and beyond what was achievable no matter how much triazole and Bravo you put on.
"If you see a wheat crop under drought stress and it rains people think it’s recovered. But in fact yield is already lost. Water stress is an under-rated effect.
"Whatever the products do it’s likely to be dose related. It’s always been more cost-effective to put on slightly more than slightly less. If you spend too much it has very little effect on margin," he adds.
Paul Drinkwater, farm manager for Abbots Ripton Farming Company near Huntingdon has already committed to using some of the new SDHI fungicide chemistry on his wheat, and has started to identify where this will be used.
"I’ve bought some Seguris so certainly some will go on the wheat that is most prone to rust. In all the information I’ve found Seguris is going to be good on yellow rust and it’s got the longevity. Improved disease control and longevity are the key things we’ve been looking for," he adds.
Other wheats will receive traditional chemistry. Most likely, he says this wlll be Amistar Opti + epoxiconazole, with the epoxiconazole dose adjusted according to disease pressure.
Jock Willmott of Strutt & Parker farming department, who manages three farms and provides agronomy on others, is planning a similar approach.
"I’ll definitely try some new chemistry. I’m very pleased we have got it," explains Mr Willmott.
"This is not the year to get disease, this is the year to protect yield. We’re going to use reasonable doses of chemistry. Yellow rust pressure is greater this spring than last year which is in favour of Seguris," he adds.
