“The break-even point is 0.2t/ha. T3s usually pay three years out of every four.”
There was more benefit where T2 sprays were delayed or ineffective, he added. “Where things have gone wrong earlier in the season, the T3 spray has greater value.”
There were three options at T3. “If you are after top-up foliar disease control for septoria, brown rust or both to protect yield, then a triazole alone will do the job.”
More broad-spectrum foliar and ear disease control, for both yield and quality, required a triazole/strobilurin mix, he said.
“This also has more timing flexibility, so if you need to go in a bit early and are looking for more persistence, then buy in a strobilurin.”
Where mycotoxin reduction was needed, through control of the fusarium species, growers should opt for a higher dose fusarium-active triazole, advised Mr Knight.
“In this scenario, you don’t need a strobilurin as you get longer persistence from the higher dose triazole. But you will need to use three-quarters rate, which won’t always be cost-effective.”
The decision was usually driven by two factors at farm level, he said. “The grain price and the conditions last year are the two main drivers. On that basis, there will be widespread use of robust T3s this year.”
The popularity of an Amistar (azoxystrobin) triazole mix at T3 was due to its ability to fulfil all the requirements of an ear spray, Dave Ranner of Syngenta suggested.
“It covers all the bases. Amistar gives the yield and greening effects, as well as controlling brown rust, septoria nodorum, Microdochium nivale and soots and moulds, while the triazole controls septoria tritici, brown rust and the fusarium species.”
It brought an extra 0.3t/ha yield over the use of a triazole alone, he said. “We’ve also recorded a 1.0kg/hl improvement in grain specific weight, which may be the difference between meeting a specification or not.”
Amistar had a big effect on Microdochium nivale, helping to prevent a potential establishment problem in the following crop, Mr Ranner added.
“Where Amistar can’t help is with the control of true fusarium,” he admitted. “So if you know you’re at specific high risk, then you need to up the rate of the triazole.
“Finances will dictate whether you can also afford to use Amistar.”
Otherwise, his recommendation was to add either prothioconazole or tebuconazole to Amistar Opti at T3. “Triazole choice will depend on the disease risk. If septoria is your concern, use prothioconazole. But if it’s rust, switch to tebuconazole.”