Weather records result in ‘patchy’ spring crops

But one record weather event has been followed by another, with April one of the driest. In Angus, just 5mm of rain fell, changing the picture a little for Agrovista’s John Murrie, while variable rainfall has brought its own issues in the Borders for Agrii’s Greig Baird.

Winter wheats in Angus have held on, refreshed by the odd shower, but winter barley has suffered, particularly on heavier land where fertiliser wasn’t washed in. Ironically, crops on lighter soils have fared better, but even here Mr Murrie suspected yields won’t be close to 2019’s exceptional harvest.

Spring barley establishment is ‘patchy’ following cultivations compromised by the dry weather. The plus point is a check on disease threats for both barley and wheat crops.

Low winter barley disease pressure saw Mr Murrie opting for an azole + strob + multisite mix at T2 plus chlorophyll enhancer (Klorofill) to promote crop greening and optimising grain fill.

Currently, septoria is stuck in the base of winter wheat, but Mr Murrie will stick with an SDHI mixture based on crop potential and a possible turn in the weather.

“Here, most winter wheat went into the ground in good time and is looking more promising. But that potential could be struck by an upturn in septoria should we have a spell of wet weather. Yellow rust and mildew are always a threat on certain varieties as well.”

He noted a spell of late season wet weather isn’t unusual, it’s more when it comes. In case it arrives between now until mid-June, he advised growers to stick with respectable rates of potent fungicide options.

With T2 sprays beyond the CTL cut-off date, he will be adding multisites Folpet or Mancozeb to boost septoria protection and to protect azole and SDHI components.

Bayer’s Grant Reid felt that despite low disease pressure, SDHI use is justified due to yield response even in the absence of disease. “Development trials with Ascra (prothioconazole + bixafen + fluopyram) showed high water use efficiency, greater root diameter and increased chlorophyll content, which form part of its label. An azole + multisite mix might give you the necessary disease protection but you might not see the same yield result.”

Mr Murrie suspected nutrient deficiencies still exist – with manganese, magnesium and boron important concerns. Further tissue testing will be required ahead of T2 sprays.

Nutrition will be an important consideration for spring crops. Dry soils have almost been ‘over cultivated’ in some situations, impairing moisture retention.

“May rainfall to date has been variable. Some areas of Angus have received towards 20mm but others as little as 6mm,” noted Mr Murrie. The danger will be if nitrogen goes straight to the grain if crops pick it up late.

Mr Murrie is worried if these crops will find a home if malting spec’ is missed. He aimed to keep crops as healthy as he can, but worried about T1 mixes being ‘too hot’.

Trace elements, particularly foliar potash, biostimulants and a PGR might also be necessary with an azole + strob mix.

“As disease pressure is light, I’ll probably go with a low rate of Jaunt (prothioconazole + fluoxastrobin + trifloxystrobin) to get the greening benefits of the strobs. Sprays will include herbicide, trace elements and possibly Canopy (mepiquat chloride + prohexadione calcium) to help root structure and stem thickness. But rates will also be low to avoid crop damage,” he said.

In the Borders where rainfall had been more up and down, there is great variability in winter crops, but it has still been extremely dry.

As in Angus, septoria is generally low in winter wheat but Mr Baird found active yellow rust in some varieties, including resilient ones like Revelation and Dickens. Mildew is also present in the base of some crops.

SRUC’s Professor Fiona Burnett said the influence of environment on the efficacy of yellow rust resistance genes is pretty strong, particularly temperature.

“This affects different genes (and different varieties) in different ways. Some are more effective at low temperatures, others at high and some are best in the middle range. So that creates variability to how well varieties withstand rust challenges year to year and site to site.”

She also pointed out that the dry weather had made plants less resilient to attack. “Rooting will be poorer and they’ve less to draw on, so yield losses will be more significant spot for spot.”

Mr Baird expected well-timed T2 sprays will deal with those disease threats but therein lies the key concern – timing. The variability between crops could possibly compromise flag leaf protection.

“Usually, as crops approach GS39, we see variation in leaf emergence even out. But by mid-May there was quite a difference in leaf emergence.

“In later drilled, slower developing varieties leaf two was just poking out, but September-drilled Grafton, sown after vining peas, was half-way through flag leaf emergence.”

With the flag leaf the most important in terms of yield response, he urged growers to be vigilant. “Go too late and the leaf will have been out and possibly exposed, go too soon and you’ll only protect that part of the leaf that has emerged. I suggest keeping a close eye on crops and ensure maximum protection.”

Compounding that T2 timing issue is the yellow rust threat. Mr Baird warned that the latent phase is often shorter than septoria. “In cool conditions, septoria cycles much slower and the latent phase can be as long as 25-28 days. But with yellow rust, it is more like 17.”

Rather than compromise flag leaf protection by pulling T2 sprays forward, he felt that a T1.5 is a better option. “You need to get on top of yellow rust so an interim spray might be necessary. It will help with T2 spray timing,” he said.

Despite lower disease severity, he warned of a long run to harvest and how quickly disease pressure changed last year. “T2 and T3 sprays might be a little ahead, but harvest won’t be and you’ll want to keep green leaf area for as long as possible through grain fill.”

Depending on variety rating and disease pressure, T2 sprays will be either Brutus (epoxiconazole + metconazole) plus Imtrex (fluxapyroxad), Boogie Plus (prothioconazole + bixafen + spiroxamine) or possibly Lenvyor Duo (mefentrifluconazole) + Imperis (fluxapyroxad) where septoria pressure is higher or yield potential warrants it. All will get a multisite and the possible addition of a strob where yellow rust threatens.

All wheats are a ‘better shade of green’ after the limited rainfall helped crops pick up nitrogen. But Mr Baird also believed nutrient deficiencies exist – potash, had joined boron and magnesium as particular concern. He will be tissue testing ahead of T2.

Only the most ‘leggy’ wheats will get PGR. Mr Baird applied robust rates of Alatrin Evo (trinexapac-ethyl) + 3C (chlormequat) at T1 and this had been sufficient to boost root structure and limit apical dominance after crops picked up nitrogen.

Winter barley disease pressure is under control. Brown rust seen in hybrid varieties is confined to untreated plots in trial sites and two-row, six-row and hybrids are all carrying significant infection.

With spring barley between early tillering and barely up, he said it shows the value of starter fertilisers. “The better crops are those that had fertiliser when sown,” he noted.

Patchy spring barley establishment applied to broad leaved weeds too, and both said growers should be mindful of herbicide cut off dates, but to try and hold applications to allow weeds to flush.

Disease-wise, mildew in spring oats might give some pointers to potential threats. But a bigger question is what patchy establishment will do for ramularia in the first season without CTL.

Ramularia thrives in stressed plants, but also preferred damp conditions. Professor Burnett said eight weeks of dry weather would reduce risk.

“Impaired tillering probably means crops will remain thin and this is likely to further check the threat from barley’s other wet weather disease, rhynchsporium. This will take the pressure off T1 sprays and put the focus at T2 on keeping the crop green,” she concluded.