Timing is again a key theme for our final CropDoctor catch-up of this season. Richard Lawrence and John Sleigh report on what are the main crop issues at this time:

Much of Scotland escaped the worst of the downpours that beset English counties over the Jubilee weekend, but we had more showery conditions as May drew to a close.

Those areas that escaped the worst of the rain were hindered by persistent winds with many spray operators forced to sneak a tank load on before the wind got up in what agronomist, Ben Lowe, described as ‘opportunist’s game.’

That means with spraying plans curtailed, some T2s had been applied late, with forward wheats passing the T2 timing some 10 days back.

“Even with operators making T2 sprays a priority, some delays had been inevitable. It’s a busy time of year with spring barley T1s, winter wheat T2s all running alongside oilseed rape second flowering sprays and potato pre-emergence sprays,” he said.

With plenty of sunlight and enough moisture in the ground, the warning from the CropDoctor team is 'don’t expect a three-week gap to T3 sprays'.

Bayer’s Grant Reid said there were noticeable differences in varieties at its Boghall, Lothian trial site. “The more forward varieties, like Extase, had half their ears out, whereas in Skyscraper the ears were just coming out.”

Ben agreed and said growers needed to be vigilant. He added that with long daylight hours crops will move quickly and suggests regular crop walking to check main tillers moving to flowering.

When it comes to timing, Grant's advice was to go when the anthers were in the middle of the ear, regardless of the gap to T2 timing. This is GS63-65.

That is because the control window is small. “Like many cereal diseases, there isn’t a curative option – there is some leeway with prothioconazole but it is small.

"If Fusarium gets established then you’ll never get it out. Mycotoxin levels are not so exacting for feed crops but Fera and Harper Adams University research has shown yield losses in the region of 10%,” he said.

Where a catchy weather forecast highlighted the danger of T3 sprays being delayed, he advised to go early, rather than hold on. “Beyond GS65 and it is past the period of effective protection,” he added.

Bayer’s Craig Simpson believed there was a solid case for an SDHI at the T3 timing this season. He pointed to untreated plots at Boghall having septoria high in the canopy, especially susceptible varieties.

He also noted some T2s being applied late as crops moved through and beyond GS37 quickly, especially if this is compounded with a susceptible variety or one drilled early.

“With activity against all fusaria species, prothioconazole is a natural fit for ear sprays. Tebuconazole is also a good option if microdochium isn’t a concern," he said.

“Both remain strong yellow rust protectants but their septoria potency has shifted over time, especially with tebuconazole. Adding an SDHI will boost septoria activity, so a product like Aviator (prothioconazole + bixafen) is a logical choice if only one SDHI has been applied so far this season,” he noted.

He also pointed out that many crops look full of promise right now and that with grain prices where they are, growers will want to optimise yield potential.

Ben noted that SDHIs may warrant a place at the T3 but pointed out that growers mustn’t dilute the fusarium element when making fungicide decisions.

“The importance of preserving quality through storage needs to be maintained. Any SDHI mixture must have a sufficient amount of azole to protect against fusarium,” he added.

He was hopeful of applying straight azole in most cases. He expected robust T2 sprays to deal with any established septoria infection in leaf 2, or the flag leaf but acknowledged that it was too early to say.

Also of note at Boghall was the amount of yellow rust in untreated plots, and even some treated ones. Craig said it was the highest level of infection he had ever seen at the site and one not noted as a yellow rust hot spot.

He felt something was afoot. “It might be weather related, but there is possibly an underlying issue. Perhaps we are seeing some change in the pathogen. In susceptible varieties, the disease is on the flag leaf of untreated plots," he said.

What it does illustrate is the importance of timing. “We’ve seen good yellow rust control this season which is primarily down to sprays being applied at the right time, particularly T0 and T1 applications. You can’t let the disease get away from you early on," he added.

Ben agreed and reckoned a fast moving azole, like tebuconazole, or strob such as pyraclostrobin (Comet), would be a useful additions for yellow rust control.

Spring barley shooting on

Spring barley had been growing so quickly that manganese deficiency has been more obvious than ever, noted Ben.

He said that despite the time it takes to get results back, he thought tissue testing was advisable. He warned that zinc, copper and magnesium could also be in short supply. These could be rectified at the T2 or with a follow up PGR application.

He also felt that biostimulants were worth looking into. Ben acknowledged that results can be variable and more research is needed, but pointed to tramline trials on his family farm using Klorofill. It hadn’t necessarily delivered greater yield, but helped straw to the extent of producing an extra bale per acre.

For Ben, anything to improve plant health and minimise the risk of ramularia is welcome. His T2 sprays were likely to be a combination of Jaunt (prothioconazole + fluoxastrobin + trifloxistrobin) with Folpet. His aim is a high loading of prothioconazole to tackle a broad range of diseases, particularly rhynchosporium.

The trip to Boghall confirms those disease risks. Rhynchosporium was creeping into untreated spring barley plots and ramularia was visible in untreated winter barley.

SRUC’s Fiona Burnett pointed out that adding folpet to robust programmes might help ramularia control, although responses can be erratic. She also said Revystar (mefentrifluconazole + fluxapyroxad) was a good choice as a the T2 programme option, although its cut-off date is an issue for malting crops.

Newly-approved Ascra Xpro (prothioconazole + bixafen + fluopyram) also offers activity. Both options rely on their azole- component for ramularia management.

She agreed that any benefit in plant health was helpful. In SRUC spring barley trials, Ascra Xpro has shown slight yield increases over former standard Siltra Xpro (prothioconazole + bixafen) coming from improved net botch and rhynchosporium control.

Fiona also referenced the green leaf retention benefits often seen with SDHI products. “We know that plant stress is a factor in Ramularia infection, so better management of other diseases combined with extended green leaf retention might help,” she pointed out.

Where winter and spring crops differ is that there is probably more variability in spring barley than winter crops. Grant notes that some spring barley crops are quite short, something Ben has witnessed on heavier ground. But he says crops on mixed farms with plenty of organic manure are in fine shape so much so that Ben thinks an additional PGR will be required

Grant wouldn’t give up on backward spring crops. With prices still riding high he says there is still plenty to play for.

Ben agrees and says that roots are searching for water. “In some areas, there has been plenty of showers but it hasn’t always delivered plentiful rainfall. But nature is doing the job – roots are looking for water. These later drilled crops are catching up,” he concludes.