June Week 3 2021
Leaf layer tested: Top 3 leaf layers
Summary: Foliar diseasecontinues to build after the gains seen the previous week – June week 3 qPCR results setting a new high for the 20/21 season.
That is primarily due to unsettled conditions across much of the country but stretched application timings is also a factor – slowed leaf emergence coupled with weather interrupted T2 sprays resulting in increased leaf exposure. Septoria tritici and yellow rust is now being detected in the all-important flag leaf at some sites.
The yellow rust situation continues to fascinate. At some sites, the disease has once again stalled with ug/ul levels falling away after last week’s spike, but at others, pressure intensifies.
Why there is no room for complacency with Septoria tritici is clear with the latest National Snapshot results.
The disease hardly registered during much of spring but is now rising sharply, resulting in a late foliar threat to wheat crops.
In Herefordshire at J P Clay Farms, Septoria tritici continues to make significant progress in the upper canopy of Extase – a ten-fold plus increase in leaves 4 and 3 at 30.710 ng/ul and 24.355 ng/ul respectively. For the first time Leaf 2 is under real pressure, harbouring 2.802 ng/ul.
Wolverine (5.3), which hasn’t been troubled of late, is also feeling some heat. The disease is now present in leaves 4,3 and 1. Despite its lower rating, levels are much reduced than those of Extase, but it is present in the flag leaf, at 0.217 ug/ul.
Close to 200 miles away and Septoria tritici is also intensifying in Insitor (6.8) and Parkin (5.5) at Ovington Hall on the Suffolk/Essex border. It isn’t in leaf 1 of either variety but is possibly heading that way if showery weather persists. Leaf 2 of Insitor is carrying 1.192 ug/ul, Parkin 0.627 ug/ul, and pressure continues to build below.
Leaf 4 of Insitor is burdened with 17.769 ug/ul, leaf 3 a fraction higher at 18.159 ug/ul. Leaf 4 of Parkin is in the high teens but leaf 3 levels much reduced. Parkin probably benefitting from a later drilling date and conditions. Slow out of the blocks, humidity hasn’t built so readily in the thinner canopy.
A few miles up the road at Troston, Suffolk, Firefly (6.8) is still troubled by Septoria tritici. The situation can be described as ‘static’ with leaf 4 pressure rising to 2.074 ug/ulbut leaf 3 falling back a little to 3.330. With its October 10th drilling date, it still perplexes CTM Ella Crawford.
The yellow rust in Insitor (5.0) at Ovington Hall has fallen back. The mini heatwave that hit much of the southeast probably helped but Ella notes that the disease is visible in susceptible varieties like Skyfall (3.0) and Kinetic (4.0) on her travels.
Where the disease is certainly visible is Greenpark, Dunshaughlin, Co Meath. Bennington (4.0) is taking an absolute battering with leaf 1 infection now a startling 34.351 ug/ul. At the turn of the month the disease could only be found in leaf 4, and then just 1.230 ug/ul.
Surprisingly, CTM James Byrne isn’t surprised. Given its susceptibility and the recent weather, he feels the inevitable has occurred. “The weather has been fair for Co. Meath but despite blue skies, temperatures have remained a little cool. Most days have been around 14 – 18 °C, ideal conditions for the disease.”
How ideal those conditions have been is that the disease is also in Conross (8.0). It is lower in the canopy, and intensity, with leaf 3 carrying 14.353 ug/ul, but still notable given its rating.
Moving further south and at Balyraggert, Co. Kilkenny, yellow rust is also in Graham (7.0) and Costello (8.0). Leaf 1 infection is low at 0.237 ug/ul and 0,642 ug/ul respectively but perhaps further evidence that the disease is no longer ‘occasional’ and limited to weak varieties.
James still considers Septoria tritici as the primary disease trait growers need to look for but says those bordering the Irish Sea need to think carefully about selecting prone yellow rust varieties.