March Week 4 2021
Leaf layer tested: Newest leaf layer, leaf 4 at some sites.
Summary: Despite reports of yellow rust symptoms in some varieties, there are still no positive results of yellow rust in new leaf layers. Septoria tritici is also restricted to the base of plants, with only a handful of positive results, and these being September drilled susceptible varieties.
With cold weather forecast this Easter weekend no immediate change is anticipated.
The divide between the north and west to south and east has disappeared. All sites are currently returning low Septoria tritici pg DNA from the newest leaves. After the disease was found at a number of sites during January and February is has fallen away – probably down to dry and cool weather for much of March and in some cases variety resilience kicking in.
The biggest turnaround is in Perthshire. The newest leaf of LG Sundance (7.9) at Keillor Farm is free of the disease and nearby at Middlebank Farm it has waned in LG Skyscraper (5.1). The disease is still present but readings dipping from 4.8 to 3.081 pg DNA.
At Middlebank Farm, George Taylor is hopeful of not applying a T0, but the crop will get some trace elements and spring herbicide. But a T0 is planned at Keillor Farm. With an eyespot rating of just three LG Sundance is a little vulnerable. This is likely to be a tebuconazole + prochloraz mix as a holding spray until the T1.
Close to 300 miles away at Long Sutton, Lincs the Septoria tritici that was present in Skyscraper (5.1) isn’t present in the newest leaf.
The question for David Hoyles is whether another follow up yellow rust treatment is needed following a pre T0 spray. Just a mile from The Wash the site is buffered from the worst of the frosts and yellow rust is a particular problem. Later drilling adds to the threat but cool weather has thwarted crop development. “In the past I’ve been happy to lose a few tillers on some forward crops, but this season with crops being more backward I want to hang on to every one we have. We’ll be going through with some micronutrition and growth regulation – the question is if the disease ‘bubbles up’ and we need some tebuconazole. Thinner crops and dry, breezy conditions have kept down canopy humidity, and disease. If it stays like this, we might be able to hold off until the T1,” he notes.
Septoria tritici cannot be found at Malshanger Estate, Hampshire either. The disease that was present in both Skyfall (5.8) and Extase (8.0) not detected in leaf 4.
In the past yellow rust hasn’t been a great concern but this season Ian Margettes and agronomist Steve Wood are planning a tebuconazole T0 for Skyfall. This is purely down to concerns over a possible new race and Skyfall’s susceptibility to the disease with its revised rating of three.
The disease control programme for Extase (8.0) will start with the T1. The question around this timing is the use of a multisite. The decision will be made nearer the time but with dry, cool weather during the latter half of March, they might just opt for a higher rate of azole + SDHI, particularly for Extase with its Septoria resilience.
New leaves at all sites are clean with no positive results currently.