May Week 4 2021
Leaf layer tested: Top 4 leaf layers
Summary: With wheat crops at or close to GS39 at most sites, the Septoria tritici that bubbled up on leaves 5 and 4 at the beginning of May has remained there. No infection is present on leaf 3 at any of the UK sites. At Long Sutton, Lincs, Septoria tritici has spread to leaf 2 of Graham, but at low levels.
It is more good news for growers. The Septoria tritici threat to the all-important flag leaf is low and the rain just arrived in time to revive crop fortunes.
That is certainly the case at G H Hoyles Ltd, Long Sutton. After 82mm of rain during May David Hoyles describes the turnaround in crops as ‘remarkable’.
With decent temperatures and plenty of solar radiation he believes wheat yields will be above the farm average - something he wouldn’t have believed back in April. “With the weather and the lack of disease we’ve managed to hang on to a lot of tillers, crops have really filled out now,”
He will be looking to keep crops green for as long as possible, and doesn’t mind a late harvest. It still could go back the other way. A repeat of June 2012 saw dull, cool conditions blunt yield prospects after a promising spring, and just a mile from The Wash, Fusarium is always a concern.
CTM James Wilkins believes the physiological benefits of SDHIs means there is a case for inclusion in T3 sprays - providing only one has been used earlier in the season.
He notes that trials have highlighted that for every day green leaf area is maintained in the upper canopy post GS39 it can be worth as much as 0.45t/ha.
And those greening benefits don’t mean a compromise with Fusarium control. “Aviator (prothioconazole + bixafen) delivers a sufficient dose of prothioconazole to manage Fusarium, plus you’re getting enhanced foliar control and greening benefits from bixafen. It could be worthwhile, especially given wheat potential, grain prices and the risk of late foliar disease.”
Over the last week there hasn’t been any great change in Septoria tritici pressure. Across all sites, latent infection is still low in leaves 5 and 4, with no great evidence of the disease moving further up the canopy.
A possible exception is Long Sutton, where leaf 2 of Graham (6.8) is carrying Septoria tritici. It is low at 0.361 ng/ul and leaves 4 and 3 are clean. Leaf 5 is still holding on to some infection, but minimal at 0.259 ng/ul.
On the Suffolk/Essex border at Ovington Hall, Septoria tritici infection in leaf 4 of Insitor (6.8) now stands at 0.705 ng/ul, not a significant rise from last week of 0.195 ng/ul. Again, the benefit of late drilling is being seen. Leaves 4 – 1 of Parkin (5.5) – sown a month later - are currently free of the disease.
Skip to the opposite side of the country, and at Cornwall it has gone slightly the other way.
Penryn farmers Oliver Bromley of Treluswell Mount Farm and Jason Chapman of Pencoose Farm are working together to compare Graham and Extase (8.0). Leaf 4 of Graham has dipped from 1.017 ng/ul to 0.838 ng/ul. At Pencoose farm, leaf 4 of Extase is carrying just 0.447 ng/ul, the leaves above it all clean. Where they differ is in development. Extase is significantly further on at GS51-59.
Even in Ireland Septoria tritici isn’t concerning Mick Marmion of Greenpark, Dunshaughlin, Co Meath or CTM James Byrne, despite may rainfall six times the monthly average.
Bennington (6.0) and Conros (5.0) are not particularly resilient against the disease so to find leaf 4 with moderate infection ng/ul 2.349 and 6.290 respectively for late May is considered unusual
For James Byrne it highlights how cool April and May have been. “It looks like May 2021 will set a rainfall record, but it has been extremely cool. Apart from the last few days of the month temperatures have ranged between 8 – 13 °C. The disease hasn’t cycled as we would normally expect to see,” he notes.
Yellow rust is only present at one site in the UK in leaf 4 on a crop of Skyscraper. However, over in Ireland at Greenpark, Dunshaughlin, Co Meath, Bennington is now carrying yellow rust on all leaves tested. James Byrne puts it down to variety susceptibility. “Bennington is a highly susceptible variety so it is no surprise, indeed the surprise is we didn’t see it earlier in the season.”
A 29th September drilled crop of Graham in Ireland is also carrying levels of yellow rust in Leaf 1, 2 and 3.