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Crop Advice & Expertise

West: Grassweed and disease control high on the agenda

Gareth Bubb says prioritising jobs is important this month, with problem grassweed control in wheat and light leaf spot sprays in oilseed rape top of the list

This month’s key messages:

  • High levels of Septoria in wheat but don’t rush in with fungicides this month
  • Apply a T0 to barley where mildew and Rhynchosporium are concerns
  • Prioritise grassweed control sprays while targets are small for better control
  • Maintain protectant light leaf spot fungicide sprays – do not delay to stem extension

Crop progress

Cereal crops are looking hungry and it is really noticeable, as plants have turned yellow over recent weeks. Growers will be itching to get on with some fertiliser.

One of the important things to come out of the ADAS Yield Enhancement Network (YEN) is the importance of maintaining tiller numbers in cereals. This is common knowledge for barley growers, which doesn’t have the ability to compensate for tiller losses, but it’s becoming clear that it’s more important than we’d realised for wheat. For that reason, the sooner that early nutrition goes on barley and wheat, the better.

Gareth’s agronomy tips for February

1. Don’t start cereal fungicide programmes too early

We have some very lush wheat crops in the West and a lot of Septoria around, but don’t be tempted to reach for the chemical can just yet. If you do start too soon, you will be locked in to spraying a fungicide every three or four weeks and it isn’t necessary at this stage. The only exception would be if yellow or brown rust is taking hold in a susceptible variety and tillers are at risk.

Some have already applied a T0 to barley to clean up high levels of mildew and/or Rhynchosporium. Where those diseases are a concern in untreated crops, consider a T0 to protect tillers, but aim to use an alternative mode of action to prothioconazole for resistance management purposes.

2. Look to complete weed control programmes in cereals

If growers have grassweeds and spray opportunities arise through February, take the chance to apply contact herbicides. I would urge growers to think about priorities and not to try and do too much all at once later in the spring.

If you have problem grassweeds present, but suspect you might get some late season wild oats, deal with the black-grass and rye-grass first when they are small for optimum control. You don’t need high temperatures, but attention to detail on application is important. Apply to a dry leaf and ensure a couple of hours drying time post-application. Even if it only means one tank per day, it will be worthwhile doing.

Monolith (mesosulfuron + propoxycarbazone) is a good option, but will need a mix partner if broad-leaved weeds are present to improve control. Hamlet is also available and its diflufenican component adds strength on broad-leaved weeds.

3. Don’t delay with light leaf spot sprays in OSR

We have picked up high levels of light leaf spot from SpotCheck testing in January and growers don’t want to wait too long before applying a fungicide with activity on the disease.  There will be a temptation to wait until stem extension/green bud, but a spray now will help keep on top of the disease, which keeps cycling and infecting new growth as it appears. Remember to treat it like Septoria in wheat – we are trying to keep it out, rather than take it out post-infection.

Fungicide rates will be dictated by what you have done in the autumn and varietal susceptibility, but any application should include a prothioconazole base. 

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