Getting the most from your wheat crop means making smart decisions throughout the season to get the best control of threats to your yield from diseases, weeds and pests.
Posted a year ago
As harvest nears there will be relief for many that this difficult season is coming to a close. Crops are a mixed bag depending on when they were drilled and whether they received sufficient rain in time.
A useful task for July/August is to take note of fields, or areas within fields, where herbicide programmes have broken down and weeds have come through. Mapping problematic areas of blackgrass, ryegrass and bromes can help you to tailor cultivations, seed rates, and herbicide programmes come autumn.
There is still time to sign up for a free trial of FieldView, which enables you to map the field into different areas. This would allow you to implement different cultural and chemical methods of weed control and assess the results, with yield data available straight off the combine.
Where weeds haven’t yet shed seeds, and if it’s possible to do so, hand-roguing can reduce some seed return which helps to gradually reduce the seedbank.
Where crops are not maturing uniformly across fields, or there is significant green weed present, consider a harvest management application of Roundup. This will reduce the quantity of green material going through the combine, and improve straw chopping and spreading. Check the harvest interval to ensure you have sufficient days between spraying and combining.
Post-harvest, take opportunities to create stale seedbeds where there is enough rainfall to encourage seeds to chit, to reduce weed burden in the following crop.
No-one needs reminding that it’s been a tough season so far. After months of rain through most of the winter and spring, we are now experiencing extremely dry conditions which is beginning to cause stress in the crops particularly on lighter soils - and with it declining yield potential - although the weather forecast early June may help restore moisture and reverse this somewhat.
So far, the lack of rain has kept Septoria prevalence down, and if we do see it it’s mainly found down at the crop base. Yellow rust, however, is still easily found at our demo sites among the untreated varieties, brown rust is expected to start becoming a threat on the more susceptible varieties. In some cases, the T2 application will have burnt yellow rust off, but it’s vital to check the crop for active yellow rust before making your T3 recommendation.
The T3 fungicide spray will help protect against fusarium ear blight and top-up foliar disease control. The decisions around T3 – what to use when and getting the dose right – are crucial. T3 needs to be applied in the middle of flowering when the anthers are visible in the middle of the ear. Timing is crucial – going past this will see a decline in control, so if are in doubt or you expect the weather may delay your application then it is best to go earlier.
If your main concerns are fusarium ear blight and microdochium nivale, then Proline (prothioconazole) used at 0.4 to 0.55 l/ha is really the only option and an outstanding choice as it’s the only triazole offering strong protection against both.
Tebuconazole (used at rates from 0.5 up to a 1.0l/ha) of a 250g formulated product will be a good mixing option if your main concerns are fusarium ear blight and rust. If it remains dry then the addition of a strobilurin (if two applications have not already been applied) will do a good job, and boost leaf greening during the yield-building period of June.
Again, it’s vital to hit the optimal mid-flowering timing and avoid the potential decline in control.
There is not likely to be any record wheat yields in 2020 but at least late April saw welcome rain in many places. This should mean the large variation of growth stages between crops starts to even out as crops push on and get hold of the nutrients they need.
Yellow rust pressure will remain depending on situation and conditions. However, the showers and warmer weather has increased the risk of Septoria development, the number one yield-reducer.
T1 sprays should mostly have happened by early May, so decisions this month are around T2 timing, assessing when GS39 is reached so that the flag leaf is fully emerged, and fungicide coverage can be maximised.
The wide range of drilling dates and local weather variations mean flag-leaf emergence is even less consistent than normal, making T2 timing decisions more complex. Full flag-leaf cover at T2 is essential but this must be balanced with other risks, not least the cut-off date of 20 May for last applications of chlorothalonil, if you have it in store.
A shorter interval means a lower percentage of flag leaves fully emerged, but leaving the interval too long means leaf two has a longer period untreated and exposed to disease.
A broad-spectrum product such as Ascra is a good choice for flag leaf sprays. It uses a unique formulation of two SDHI fungicides (bixafen + fluopyram) and the most effective azole partner (prothioconazole) to give effective all-round control. And assuming the wet weather continues, a product such as Ascra – which is rainfast in minutes with the Xpro formulation – may prove a wise investment.
Priorities for May:
Spring is finally here but the impact of the previous wet weather has left its mark on wheat crops, and this could hinder disease control this season. As fields got drilled at some point between September and late February, the diversity of growth stages seen in the surviving crops poses a challenge in finding the right timing for fungicide applications.
Identifying leaf 3 emergence is crucial to get T1 timing right. With the later drilled crops racing through growth stages and plants dropping the odd leaf, leaf 3 could emerge earlier than you might expect looking at nodal development.
It is always important to avoid compromising T1 protection – but especially in those crops that have not received (and will not receive) a T0 application. Although directly dissecting samples in the field to assess growth is extremely challenging, identifying leaf 3 emergence in crops is crucial to ensure they are fully protected. Richard Cromie, an independent agronomist, shows the 5 key steps to identifying leaf 3 in this video.
T1 sprays this April should consider the crop susceptibility for diseases based on drilling date and disease rating. Even though late drilled crops are likely to be under reduced pressure from Septoria, other threats such as yellow rust, mildew and eyespot should also be considered.
In the current scenario, a flexible, all-rounder product like Ascra (bixafen + fluopyram + prothioconazole) can be ideal where any of those diseases are a concern, but especially Septoria or yellow rust. Ascra’s dose flexibility means it is easily matched to suit varying crop development and disease situations.
For the most resilient Septoria varieties, there is still a place for Proline (prothioconazole) + chlorothalonil but the gap to GS39 must be kept short.
Priorities this April (location dependent):
The impact of autumn and winter wet weather is still evident, with a good proportion of the season’s crop area not planted. As we enter March the likelihood of those fields being planted with winter wheat diminishes further.
Perhaps the one small silver lining in this year’s weather is that if and when ground conditions improve, there should be a good opportunity to get on top of black-grass with Roundup in the fields that will now be destined for spring cropping.
For those who have managed to drill winter wheat, consider the scenario you face. If you have any grass-weed concerns, coupled with broad-leaved weeds, then Pacifica Plus is an ideal partner, new for spring 2020. If black-grass is the primary concern then Monolith remains the tried and trusted specialist.
When planning disease control programmes for this season, consider how delayed drilling will influence disease pressure. Any late drilled crops are likely to be under reduced pressure from Septoria however, other threats such as rusts and mildew may be more prevalent.
This combined with the considerable variability likely to be seen in crops this season, means fungicide control and timings could be difficult to judge, and flexibility in dose will be key. An excellent all-rounder, such as Ascra will be ideal in these conditions, and ticks all these boxes.
Priorities this March (location dependent):
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Find out more information about the key disease threats to your wheat crop. For each disease you can learn how, where and when the disease infects wheat, average yield impact, symptom recognition and our advice on appropriate control strategies.