Tailor well-timed T0 sprays to combat disease threat

Wheat growers are advised to walk their crops carefully before applying T0 sprays to ensure they match chemistry to disease threat and apply the spray at the right time.

“The detection last year of yet another race of yellow rust has undermined further the reliability of wheat resistance ratings,” says BASF business manager Ben Freer.

“The only way to be sure is to get out in to crops and see what’s there. The winter will have dampened down infections but if the disease was present earlier and has apparently disappeared, don’t be fooled. It will return.”

The T0 spray also provides a solid start to the Septoria control programme, clearing up disease in the bottom of the crop and protecting new growth, says Mr Freer.

“T0 should be applied as leaf four emerges, within three weeks, and a maximum of four weeks, ahead of the T1 (GS 32) spray. If you apply it too soon you risk stretching the T0-T1 interval, which could compromise the whole fungicide programme.”

As an approximate guide, the T0 timing usually falls at beginning of April in England and a few days later further north, but could be earlier if the weather warms up.

T0 applications are cheap insurance as they are protectant only. Expensive curative chemistry is not needed, says Mr Freer.

He recommends chlorothalonil (CTL) at 500g/ha to provide early Septoria control. “A half-rate epoxiconazole, as contained in Opus Team or Capalo, should be added for rapid control of yellow rust and to provide additional protection against Septoria,” he adds.

“If rust is a problem and you are not planning to use a strobilurin later in the programme you could use Comet to knock it out.”

Farmers assessing crops

Three of BASF’S Real Results growers, one in the north, one in the east and one in the west of England, are assessing crops with a view to T0 applications.

Russell Price of Bishop’s Frome in Herefordshire says: “Thanks to a really good autumn and one of the kindest winters crop-wise for a long time, the wheat is looking fantastic. There’s a bit of Septoria on lower leaves but no rust about.”

Russell McKenzie, manager of John Sheard Farms, Bedfordshire says: “We didn’t start drilling until the 12 October, so generally everything seems to be a little bit cleaner.”

In Yorkshire, Richard Hinchliffe of HInchliffe Farms says his winter wheat looks good. “There is a bit of Septoria down the bottom but it is only the start of March, so it’s to be expected.”

To date (second week of March) none of the growers had seen any yellow rust in their crops.

Mr McKenzie says he is conscious that yellow rust could bubble up in the right conditions. “However, we still have good eradicant options. Triazoles will still do a good job and strobilurins are still quite effective.”

Mr Hinchliffe has used a triazole-free T0 for the past couple of seasons. “Depending on variety, we will either go with straight CTL or CTL plus strobilurin, if it is second wheat or we think it will benefit from it.

“Basically the T0 spray is a fire break. It’s dampening all that winter disease down. We’ll get serious with the T1 spray and then really serious at T2.”

Ian Oliver, agronomist for Russell Price says the T0 provides some flexibility on the T1 application timing especially if there is a weather delay. “We will apply CTL for Septoria and most probably a mildewicide, as there seems to be a lot of mildew in crops. Some varieties, especially Reflection, may have tebuconazole or epoxiconazole at T0, just enough to keep a lid on any yellow rust.”

Coping with T0 delay

If bad weather delays the T0, growers can to choose from the following options, says Mr Freer.

• If within seven days of GS32 it may not be worth applying the T0, unless if a long period of bad weather is forecast, which could risk delaying the GS 32 spray.
• If only the tip of final leaf 3 is visible, it is still worth applying the T0 as temperatures at this time of year can fluctuate widely and leaf emergence can be slow.
• If leaf 3 is half to three-quarters emerged, then T0 should be abandoned and the focus should switch to T1.