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Crop Advice & Expertise

What’s happening in fields in the North West this May?

Rozzi Martin discusses disease threats in wheat, barley and oilseed rape this month and gives recommendations on how to stop them denting crop yields.

At a Glance

This month’s messages

 

  • Septoria the main disease threat in the region’s winter wheat crops
  • Ascra proven to give the strongest control of septoria and is best fit at T2
  • Maintain prothioconazole use through wheat programmes for suppression of stem-based diseases
  • Levels of Rhynchosporium and net blotch is high in winter barley
  • Inclusion of a CTL product at T2 a must for ramularia control
  • Tailor sclerotinia fungicide programmes based on risk and length of OSR flowering
  • Prothioconazole offers best all-round option for flowering sprays

Winter wheat

The tough spring conditions in the West have meant only about 50% of T0s were applied to winter wheat and most have turned to a robust azole and SDHI-based T1 spray. There are particularly large variations in growth stages across different varieties and drilling dates, so it is more critical than ever to walk fields and dissect plants to be confident fungicides are targeting the appropriate leaf layers – T1 at leaf 3 fully emerged and T2 at Leaf 1 fully emerged.

The cool, wet start to the year has seen a higher incidence of eyespot, which can be easily found, particularly on varieties with weaker resistance ratings, including Siskin and Graham. In fact, only 6 wheat varieties on the Recommended List have an eyespot rating higher than 5. Whilst earlier in the programme is the best time to get control of eyespot, an eyespot active fungicide such as prothioconazole at T2 will contribute to reducing eyespot levels.

Septoria is the main disease threat and Ascra (bixafen + fluopyram + prothioconazole) has been proven to provide the best septoria control available. In high disease pressure situations or where applications have been delayed significantly, increase to the full rate of 1.5L/ha to maximise eradicant activity. In lower pressure situations 1.0L/ha of Aviator (bixafen + prothioconazole)will still give excellent, cost effective disease control.

Avoid confusion between high disease pressure and requirement for curativity. The focus should be on good application timings and only where applications are delayed should there be a real concern around curativity.

So far, yellow rust has been at particularly low levels this season, only appearing later in weaker varieties such as Reflection. Therefore, a well-timed azole and SDHI septoria-focused T1 and T2 application will be enough to keep on top of this disease in most varieties.

Fusarium control

Stem based browning common, which could be associated with eyespot or potentially microdochium – one of the species that can produce fusarium ear blight symptoms later in the season. In addition, CropMonitor is also finding Fusarium graminearum on the leaf layers, all of which is indicating that there is inoculum building up at the ground level.

Prothioconazole is best azole for all-round activity on true Fusaria and microdochium, primarily at T3, but using it at T1 and T2 in products such as Aviator and Ascra also contributes to reducing inoculum levels.

After the blast of heat in the middle of April, the weather has reverted to more catchy conditions and choosing a good rain fast product will ensure good protection. All the Bayer Xpro range, including Aviator and Ascra, have a superior Leafshield formulation, which gives the best spreadability and drying time and are rain fast within minutes, giving you the confidence that your crops will be protected despite the occasional rainfall.

Winter Barley

The wet spring has seen high levels of rain splashed diseases Rhynchosporium and net blotch in winter barley in the West this season. Ramularia should be a key consideration at T2 with more widespread SDHI resistance appearing last season. Therefore, the use of chlorothalonil is critical at the T2 timing.

Fandango at 0.75L/ha + CTL will be a cost-effective option in lower disease or lower yield potential scenarios. In higher disease pressure situations or high yield potential sites, Siltraat 0.4L/ha + CTL will give good disease control. A higher Siltra rate of 0.6L/ha will be particularly beneficial in the north, where green canopies can be maintained for longer. Apply T2s from GS39-49. The optimum timing for ramularia is GS45-49 before symptoms develop. Ensure the T1 to T2 interval is no more than 4 weeks.

Oilseed rape

With the burst of sunshine in the middle of April, the oilseed rape crop finally came into flower. This, however, coincided with an increase in the risk of sclerotinia infection, which has the potential to cause a yield loss of up to 50% in severe cases.

There is no curative activity against the disease so control must be preventative and applications well-timed. However, if they are applied too early, sclerotinia risks developing towards the end of flowering. The optimum timing is early to mid-flowering before any significant petal fall.

A single application can be enough for some years and sites, but if flowering is prolonged, disease risk is very high or there is a history of severe outbreaks on farm, this can be followed with a second spray three weeks later. Proline (prothioconazole) offers the most cost-effective control of sclerotinia and light leaf spot, plus has useful effects against powdery mildew and alternaria. Therefore, I would recommend Proline (prothioconazole) at 0.46L/ha at early to mid-flowering, followed by 0.32L/ha of Proline three weeks later.

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