In this month’s Crop Walk and Talk Andrew Roy of Frontier, highlights agronomy issues affecting wheat, barley and oilseed rape crops in Stokesley, North Yorkshire. Abby Kellett reports.
At Frontier’s Stokesley trials site, crops had just received their first proper dose of rain in six weeks, having only had around 20mm throughout April.
While the lack of rain had stunted crop growth on some lighter land, it had helped keep disease in check. However, the change in weather is likely to promote disease development, particularly of septoria, according to Mr Roy.
He said: “As we head towards the T2 timing in wheat, which is when the flag leaf is fully emerged, the key consideration for us in the North East is septoria, arguably the most damaging wheat disease.
“Some of the newer varieties like Graham, Costello and Siskin give us a vast advantage in terms of their inherent genetic resistance to septoria and they allow us to adjust programmes slightly, while some of the older varieties, Santiago for example, would be much more vulnerable to septoria and would need a fairly intensive programme.”
He warned that recent rain has encouraged movement of septoria to the upper leaves via rain splash. This will be followed by a latent phase before the disease expresses itself on the all-important top three leaves.
“Yellow rust has been an issue throughout the season but actually on this site it did not show itself until about a month ago when we saw the first sign of pustules developing.”
Untreated plots with poor resistance to yellow rust, such as Reflection, have been ‘devastated’ by the disease.
“The flag leaf is hanging on but you’ve got yellow rust not only onto leaf 3 and leaf 2, but there are yellow rust spores covering the soil surface as well.
“Mildew has been sporadic and at quite high levels in varieties like Leeds, so we need to address that and so use of a mildewicide could be a necessity at T2, alongside your triazole and SDHI mixtures.”
With most OSR crops in the area at late flowering, Mr Roy said the main consideration for growers should be whether a final sclerotinia spray is required.
“Petals are starting to drop off crops and now we have some humidity and rain, we need to consider the threat from late sclerotinia.”
Warmer temperatures have also led to an increase in seed weevil activity at the site. “Seed weevil is actually an indirect problem, because the seed weevil burrows a hole through the pod and gives access for the bladder pod midge to lay its eggs. The bladder pod midge is potentially the more damaging of the two pests as it can cause premature shatter of the pod.
“If seed weevils are found above the threshold, growers need to think about adding a pyrethroid in with the sclerotinia spray.”
Having reached full ear emergence, the difference between barley crops which had received a fungicide-PGR application and those which had not was noticeable. As well as the difference in height, treated crops boasted much longer ears containing larger grains.
“There is a big difference in ear size because you increase the grain to straw ratio by adding a PGR into the programme, it’s something we frequently see.”
Having started the season with high levels of mildew, dry weather from mid to late spring helped check the disease, but some susceptible varieties were still displaying symptoms. Similarly, dry weather helped suppress rhynchosporium spores, said Mr Roy.
However, ramularia remains one of the biggest threats to barley crops in the area, a disease which proved problematic last season.
“The simple solution to ramularia is chlorothalonil. Because it is a multi-site it has fewer resistance issues than other fungicides so it is a fairly essential ingredient at the T2 timing and should be backed up with triazoles and strobilurins or SDHIs, depending on variety and risk,” said Mr Roy.