Spring spraying advice as crops get moving at last
3rd April 2018
With the T0 timing approaching rapidly, there are good reasons not to be tempted to miss the first fungicide spray, says Chris Bean, technical director of Zantra. Septoria is easy
With the T0 timing approaching rapidly, there are good reasons not to be tempted to miss the first fungicide spray, says Chris Bean, technical director of Zantra.
Septoria is easy to find in wheat crops drilled before November, so there is potential for it to spread up the plant as growth takes off, while PGR programmes should start at T0 to avoid a repeat of last year’s lodging problems, he advises.
“With disease, it will all depend on the rainfall we get from now on, but the first spray timing allows us to manage any inoculum already present,” he comments. “A T0 has given a consistent yield response in our trials, not just in rust situations.
“Don’t forget too that windy conditions allow leaf rubbing to take place, which is another way that septoria can spread.”
Zantra trials results show a 0.3-0.4t/ha response to T0 sprays, depending on variety, season and importantly choice of T0
fungicide, highlights Mr Bean. “These are relatively low-cost treatments which have both a disease management and a yield enhancement effect.
“Remember that the ‘green bridge’ provided by cover crops and stubbles with volunteers can also harbour disease – even brown rust infections begin in the autumn, even if it doesn’t appear at severe levels in crops until later.”
Any lodging risk should be managed by getting PGRs on at T0 and T1, with subsequent crop growth and conditions then influencing decisions on late season use. “Most growers will want to do more with PGRs this spring than last, which means getting the early applications right.”
For the first application, chlormequat should be used along with either trinexapac (as in Trinexis and Moddus) or Canopy, with a follow up at T1, he suggests.
“Soils aren’t warm yet, so any thin, backwards crops might benefit from a foliar feed containing phosphate, such as PK Plus, at the same time. Roots struggle to take up phosphate from the soils at temperatures below 10°C.”
A nutrient and PGR application will also help promote tillering where crops are behind, he notes.
Both brown rust and yellow rust have been knocked back by the snow and frost for now, but mildew remains lively in places, adds Mr Bean.
“It’s a fairly standard picture as we come into the T0 timing. In the south, leaf 4 will be fully emerged by next week in most crops, so spraying will begin in earnest after Easter.”
He is recommending T0s on all wheat crops drilled by the third week in October. “Only the very late drilled crops can wait until T1 for their first spray – although a PGR plus nutrient mix to encourage tillering might be a useful replacement for the traditional T0. On the others, there is too much at stake to ignore the T0, especially where nitrogen has been applied.”
A triazole/multi-site mix will be used in most situations, with a bit of mildew activity included where necessary.
“That means that the T1 timing won’t be compromised – it can take place in the last week of April, some three weeks after the T0, as planned.”
Nitrogen top dressings are up to a month later than planned this spring, so some cereal growers will find that they end up applying the total fertiliser requirement in two rather than three splits.
Applications that should have been made in late February have been going on over the last few days, so there will be situations where it’s better to roll some of the first application into the second one, advises Chris Bean.
“There’s no need to amend the amount you are planning to apply, just make sure that it is there when the crop needs it,” he says. “If that means putting it on in two applications, instead of three, that’s fine.”
Any nitrogen applied earlier, before the snow arrived, is likely to have leached down through the soil profile as conditions thawed, he warns.
“Don’t expect to see an immediate uplift in these crops, as the early applications won’t have been of much use.”
Drilling of spring barley, wheat and pulses is also later this year, with some catching up to do. “There is no point in rushing crops in, soils remain cold and are drying quickly on the surface, but remain wet underneath. The same is true in winter crops, especially where minimal disturbance establishment systems have been used and water has drained away well.
“It may seem as though we’ve had a very wet winter in the south, but the reality is that there has been some rainfall on most days, rather than huge amounts.”