With yellow rust established in a number of crops, growers are being advised to stay vigilant and weigh up their control options.
Procam Agronomist Paul Gruber has picked the disease in Champion, as well as Palladium, Vibe and Typhoon.
To compound matters, he describes the level of septoria bleaching in crops drilled early in October crops as ‘unprecedented’, a huge burden of inoculum waiting to work its way up the crop as the season progresses.
He wouldn’t rule out adding something to T0 sprays for the more susceptible varieties if the conditions remain conducive, advising a multisite or elicitor over prothioconazole, which will feature later in the programme.
Further North, colleague Nigel Scott was one of the first to see the disease appear in varieties thought to be resilient last year. He too, is also finding the disease present in a number of varieties and says the threat has to be factored in as growers start to plan early-season disease control strategies. “It is a disease that you can’t let get away from you,” he cautions.
In East Anglia, Velcourt agronomist Louise Nobbs is a little puzzled by what she is seeing.
On some farms, yellow rust is very evident, particularly in Champion, Skyfall and Extase, but on other farms, the disease is not yet evident.
What she doesn’t know is why and whilst a number of interacting factors could be at play, what is evident is that the proportion of susceptible varieties in the ground and the mild winter means that a robust approach is essential. With many of these varieties, it is not a question of ‘if’ but ‘when’. n ideal conditions, the disease can cycle in as little as a week and early control is key.
Yellow rust is fairly easy and inexpensive to control and Louise is likely to favour a combination of tebuconazole and azoxystrobin at the T0 timing. The question is, will she need to go earlier?
She is reluctant to pull T0 applications forward and stretch the window between T0 and T1 applications, but she might apply a fungicide before T0 if disease is evident in the crop. “What’s important is to ensure the gap to the T1 doesn’t get stretched, and I don’t want the T1 timing compromised given the levels of septoria I’m seeing. A pre T0 to keep a lid on yellow rust might have to be the case.”
Cambridgeshire grower Russell McKenzie is also a little perplexed with the yellow rust situation. Rated at three, there are few varieties as susceptible as KWS Aintree, yet it is clean. On the other hand, some crops of Bamford are “full of it”. He has earmarked tebuconazole for T0 sprays. With its performance possibly tailing off. he will up the rate to 1.0 l/ha.
For those crops under the highest pressure, a strob might be needed to boost persistence. With only two applications allowed, he would prefer to hold for later timings but it might not be possible.
