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 2 weeks ago
Dry weather throughout much of April has helped to keep many diseases at bay, with Septoria noticeably remaining at the bottom of the canopy on leaves five and six. The lack of rain also helped to facilitate the timely application of T1s at the optimum timing across most of the UK. Overall, the Septoria pressure has been lowered on many crops.
Yellow rust risk, however, increased slightly towards the end of April with the cooler conditions, which favoured disease progression on susceptible varieties.
The priority in May will be to apply T2 fungicides within three weeks of T1s. This will ensure that fungicides don’t run out of steam and maintain protection to crops through critical growth stages.
T2s should be applied when the flag leaf is fully emerged, with a fungicide that predominantly targets Septoria. Where yellow rust is a concern, this should also be targeted, along with brown rust in the south, which can become an issue.
Bayer’s CropCheck service can help you get a better understanding of what diseases are present in your crop before you see symptoms, and compare varieties, drilling dates, different fungicide programmes etc. All you need to do is complete our form and send in a leaf sample. You can also look at the National Snapshot Live results to see how disease is progressing in commercial wheat fields in your area.
For all round disease control 1 – 1.5 L/ha of AscraXpro, depending on variety, disease present, and drilling date, will give good results. For varieties drilled before 14 October, a rate of no less than 1.2 L/ha is required.
Weed control will continue to need some attention during May. Watch out for any late-emerging broad-leaved weeds, and don’t forget wild oats. These can germinate quite late and cause significant yield loss. Pacifica Plus can be used up to GS39 to control a wide range of broad-leaved weeds and wild oats.
Finally, a leaf tissue test can help to ascertain any other crop nutrient requirements to support yield.
Throughout March the mostly warm, calm, and dry weather has allowed plenty of progress to take place, including finishing off grass-weed control, and making a start on T0 fungicides.
Disease pressure is currently average for this time of year, although Septoria and Powdery Mildew can readily be found in crops, and Yellow Rust is increasingly being found in some varieties.
T1 fungicide timings will fall, for most, within April. It is vital to get the timing right, since this is the main building block for season-long disease control, focusing on Septoria, Yellow Rust, Eye spot, Powdery Mildew, and reducing Fusarium infection. Septoria and Yellow Rust have the greatest impact on yield, so the choice of product and rate at T1 is crucial.
However, timing is just as important. Aim to apply T1 fungicides when leaf three is at least three-quarters or fully emerged. Try to time applications so that the gap between T1 and T2 applications is around three weeks to avoid T1s running out of steam if Septoria and Yellow Rust disease pressure is high.
Varieties with good resistance (rated seven or higher) that were drilled in November or later, are likely to be under less disease pressure and growers have the option of either AscraXpro at 1 L/ha or Aviator 235Xpro at 0.8 – 1 L/ha.
Crops that will be more susceptible to Septoria (drilled earlier and/or with lower resistance ratings), or any crops that didn’t receive a protectant fungicide at T0 should consider using a higher rate of AscraXpro at 1 – 1.2 L/ha. The choice of rate will also be dependent on the levels of disease in the crop at the time of application.
Latent Septoria and Yellow Rust can now be identified using Bayer’s CropCheck initiative, before disease is visible in the crop. This can help to play a part in decision making. Find out more about CropCheck and look at the National Snapshot Live results to see how disease is progressing in commercial wheat fields in your area.
Eyespot and Fusarium can sometimes be overlooked at T1, but most varieties in the ground this year have low tolerance to Eyespot in particular. A wet and warm April could drive disease, particularly in second wheats, and wheat drilled into last season’s stubbles where inoculum is present in the trash. Wet weather last season drove Fusarium infections, with high levels of inoculum carried over to this season’s seed, which could cause issues later in the year.
For both Eyespot and Fusarium reduction, AscraXpro at 1 L/ha or Aviator 235Xpro at 0.8 L/ha will provide good levels of protection.
February to March
The late winter storms in February meant that very little field work took place, as it was almost impossible to get machinery onto wet land or was too windy for spraying. However, completing grass-weed control is now a priority in March.
While many crops are looking clean after good levels of weed control from residuals and top-up applications, some grass-weeds remain. It’s important to finish the job to minimise seed return the following year.
For grass-weed and broad-leaved weed control, Pacifica Plus at 0.4 kg/ha is a robust solution, however if brome is the main weed present, increase the rate of Pacifica Plus to 0.5 kg/ha for better control. Alternatively, Monolith at 0.333 kg/ha has shown good control of soft, meadow and rye brome species in Bayer’s weed screens.
As soil temperatures start to rise an application of nitrogen can help to promote tillering, and leaf tissue samples can be taken to determine any other nutritional needs.
T0 timings normally begin at the end of March in the south of the UK, identified by the crop reaching GS30, when the first node is detectable. The main driver at T0 is to control the risk of yellow rust, which has been on the increase in several varieties over the past few years.
If yellow rust is the only disease issue or risk in the crop, 100 – 150g/ha of tebuconazole will be sufficient. However, if Septoria is a threat, the multisite Folpet will hold off disease until the key T1 timing.
Some powdery mildew is being reported in more forward crops. This is best dealt with using a mildewicide if it’s the only issue in the crop. But where yellow rust is also a threat, there is the option of a low dose of tebuconazole and prothioconazole which will keep both diseases at bay until T1.
December to January
This autumn has so far been the opposite of 2020 and 2019, with very favourable conditions for drilling and establishment, albeit rather dry in November. This has provided an extended drilling window with nearly all crops in the ground before Christmas, which has been especially helpful where wheat is following root crops.
Residual herbicides have done a very good job this season, and by the end of November most crops had also received a top-up residual application.
Where grassweeds have come through residual programmes, and if weather conditions are favourable in December, these crops will benefit from a contact herbicide application before Christmas. Atlantis OD, Hamlet, or Othello, can be used to gain good control of black-grass and rye-grass, and a range of broad-leaved weeds.
It’s important to remember that ALS herbicides work more effectively when the target weed is actively growing, so timing is critical. Periods of hard or prolonged frost will slow active growth.
Where grassweed populations are too great in drilled crops, there is still time to spray-off and re-drill this winter. This option is being taken by some growers with extremely high black-grass challenge.
Crops have been under greater pressure from slugs this autumn, but as temperatures drop both slug and aphid activity will reduce. However, if we experience mild temperatures in December this could prolong the threat, so crops should continue to be monitored.
Yellow rust is sometimes seen in crops at this time of the year, but once adult varietal resistance kicks-in, further disease development will be prevented. Disease control is rarely necessary to control disease in the autumn and early winter.
Over the past few seasons we have seen a shift in population strains of yellow rust. If disease is seen before Christmas, it is worth monitoring the varieties in which it is present, as this will help with disease control decision making in the spring.
By the end of October, around 80% of drilling had been completed, with wheat plantings up on previous years’ average.
Where wheat is still to be drilled following maize, potatoes and/or sugar beet, it’s important to review seed rates, and increase to 400, 450, or 500 seeds per square metre depending on the soil type.
Where crops have already been drilled, the focus has turned to weed control.
Crops that were drilled in September may require a top-up with a residual herbicide. If six weeks has passed since applying Liberator at 0.6 L/ha, then a top-up at 0.3 L/ha can be applied. Alternatively, 0.5 L/ha of metribuzin in Octavian Met or Alternator Met gives increased grassweed control as well as important broadleaved weed species, including groundsel, cranesbill, and poppy.
Where grassweeds have established through a residual application, or if none was applied, 1.2 L/ha of Atlantis OD alongside a residual partner (top-up or full rate depending on previous applications) can improve control of black-grass at the 1-2 leaf stage.
Crops that will be drilled from November onwards should be through the worst of the black-grass germination period, and an application of 0.6 L/ha of Liberator with or without another herbicide partner, should be sufficient for most scenarios.
Depending on the temperatures in November, aphids may still need monitoring and an application of insecticide if the T-Sum threshold is met, to protect crops from barley yellow dwarf virus (BYDV).
Slugs are an increasing problem in cereals crops, particularly on heavier land. Slug grazing will be the main activity to watch for in September and early-October-drilled crops, while later drilled crops should be monitored for seed-hollowing. This is the last winter that growers may use metaldehyde slug pellets (up to 31 March 2022), and the full Metaldehyde Stewardship Guidelines should be followed when using this treatment. Ferric phosphate slug pellets are an alternative option.
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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.