Topical wheat disease control issues debated

  • Are T0s essential?

Perhaps surprisingly, the issue of T0s wasn’t clear cut. James Alford, Velcourt‘s trials manager, was a clear advocate of the practice suggesting at least 80% of Velcourt-managed wheats would receive one this season. That was up from 65-70% from last year. “The only ones missed will be late drilled or highly resistant varieties.

“It is a risk management tool in case you get delayed at T1,” he explained. “Our trials have shown a yield response from T0 four years out of five.”

It also helped counter any rust holes of Proline (prothioconazole), he said. “Where we used a T0 we didn’t have any problems controlling rust with Proline.”

Independent agronomist Sean Sparling, from Lincolnshire, was slightly more sceptical of T0s. “Closer to 30% of my wheats will get a T0. If it gets anything it will be Bravo plus low dose triazole, unless there is a massive amount of rust.”

The timing was logical if rust was the issue, Steve Parker, a researcher from the Central Science Laboratory in York, said.

“But I have a problem with them for septoria control. It can work with a specific timing so you create a green bridge, but it is really difficult. If you’re going to put on high rates of triazole put it on leaf three.”

Despite that warning, Norfolk Sentry Farms‘ farm manager, John Barrett, was planning to use T0s. “We’ve got sugar beet, so it helps as a management tool with timings.”


  • Should growers be spending more on fungicides?

Whether growers should spend more on fungicides this season, given higher grain prices, largely depended on what previous programmes were, the table decided.

Velcourt programmes were unlikely to change too much, Mr Alford said, other than to allow for an increase in the cost of product. But the firm had already been committed to robust doses at the main timings and using T0s in past seasons.

Those were the two areas where other growers might look to increase their expenditure, along with ear sprays.

“Some growers have pared back their spending,” Alison Daniels of Bayer said. “I can see people with that borderline approach moving up, and increasing dose to get a little more latitude [with timing].”

Mr Sparling’s advice at T1 and T2 is unlikely to change. “If it was the right way of doing it at £60/t, it will be right at £200/t because we were looking to optimise output. But we wouldn’t be below three-quarter dose triazole plus a robust strobilurin on the flag.

“The things most likely to change are T0 and T3. T3 is an added complication [with the new mycotoxin rules], so will be an extra spend. There used to be no benefit on non-high value crops, but the price this year justifies it. You need to keep them healthy to the end.”

Mr Barrett looked at spending from a slightly different perspective. “We aim to spend around £6/t on fungicides. I expect a lot of any increase this year will come from higher prices too. But the upside is a lot higher so there is the opportunity to spend more, wisely.”

  • Will prochloraz help manage septoria resistance to triazoles?

The panel was united in its opposition to using prochloraz as a tool to manage septoria resistance to triazole fungicides.

“There has been a lot of hysteria about azole sensitivity, which I feel has been raised unnecessarily,” Dr Parker said. “There is no evidence of programmes failing despite rates going down. I would be careful about the science and how it is being interpreted.”

The science wasn’t in place yet, agreed Dr Daniels, although her colleague Nigel Godley said investigations had identified different effects from prochloraz on various mutations, but hadn’t seen any additive disease control in the field. “The big danger is substituting some prochloraz in for one of the more active triazoles. It won’t do as good a job as you would with the higher dose of Proline, for example,” he said.

Mr Alford suggested its use was “a red herring”, while Mr Sparling advised “sticking with what you know works” this season.

  • Will broad-brush fungicide programmes become the norm?

A broad-acre approach using fewer chemicals that could cover the disease spectrum across most varieties simplified programmes for both farmers and agronomists, Mr Barrett and Mr Sparling agreed.

“The fewer varieties you grow, the simpler it is, and it makes it easier to hit timings,” Mr Barrett said.

“Logistically you don’t want to be spraying five different things at the same timing,” Mr Sparling noted. “I try to keep it to two different brews at T1 and T2. Growers don’t want complicated – they want simplicity. If I had to tailor programmes to individual fields I would be out of business. An agronomist can do simplicity because technically it is the right thing to do.”

Broad-spectrum products, such as Proline, helped, Dr Daniels suggested. “Regardless of location and disease pressure our trials have shown a consistent 0.2t/ha benefit over epoxiconazole.”

But Dr Parker warned against going too far down a prophylactic route. “Given that variety and seasonal differences are enormous I would find it disappointing if ideas were set.” Good management was being able to measure and adjust to take into account changing conditions, he said.