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Crop Advice & Expertise

What’s happening in fields in Norfolk this March

Light leaf spot infection is high in OSR crops for Jack Hill. He also looks ahead to the T0 fungicide timing in wheat, where susceptible varieties will require treatment

At a Glance

This month’s messages:

  • High levels of LLS infection in OSR crops across Norfolk
  • Prioritise OSR LLS fungicide sprays where risk is high
  • Plan a rust-active T0 in susceptible wheat varieties
  • Beware including contact herbicides in complex tank mixes at T0

It is wet in Norfolk and there hasn’t been much field work completed in recent weeks, except for the odd field destined for a spring crop being sprayed off with glyphosate. The last of the sugar beet has now been lifted.

Oilseed rape

Getting some nitrogen on to OSR crops will be at the top of the priority list for most growers once they can travel. Where we have carried out disease sampling using the SpotCheck service since Christmas, results have been showing high levels of light leaf spot. Although the recent cold snap will have slowed the disease, a detection rate of 70% highlights the need for treatment as soon as possible.

Growers will be tossing up whether to wait until stem extension to apply a fungicide, but as light leaf spot is a polycyclic disease, its lifecycle will continue unless a fungicide is applied. Look at your varieties’ resistance scores and whether it had any treatment in the autumn and prioritise a separate spray ahead of stem extension where necessary.

Where holding off to stem extension, ensure any fungicide application contains an active with good activity on light leaf spot, such as prothioconazole. Like septoria in wheat, the disease needs to be treated protectantly and if you see the disease in the crop, it is too late.

With earlier-flowering OSR varieties now dominating, plants are often past the susceptible stage at green bud by the time pollen beetle numbers increase. However, with the late spring this year, one potential consequence could be an increased risk of pollen beetle damage. This is due to crops being less developed as the migration starts and is something growers need to keep an eye on.

We have an OSR variety demonstration trial at Morley Farms near Wymondham this year and we are starting to see interesting differences in spring vigour. Growers are welcome to come and have a look on 5 April between 9am and 1pm.

Cereals

Cereals have come through the winter with good plant numbers and once soil temperatures start heading in the right direction and nitrogen is applied, they will be in a very good place.

I haven’t seen a great deal of yellow rust in wheat, but there is a little bit of septoria bubbling away in the bottom of crops. If it warms up, its latent period will start to shorten. In winter barley, mildew has been an issue, but the cold conditions have stopped it in its tracks.

For wheat, the T0 timing towards the end of March is the ideal time to start rust programmes on susceptible varieties. You get good knockdown activity from the strobilurins and non-primary azoles provide good persistent activity within the leaf. Keeping rust out early will allow you to focus on septoria control at subsequent timings, which is important, as it’s the most difficult disease to manage.

There is potential drop the T0 spray on later-drilled and more resistant wheat varieties after roots, as they will be carrying less disease. However, my advice is if you are going through with a PGR anyway, the addition of straight chlorothalonil is cost effective and will ensure you aren’t putting all the emphasis on getting the T1 timing spot on in April.

There was a small window for applying post-emergence contact herbicides in February and some took their chance. However, for others, jobs are now concertinaing and growers might be considering applying large tank mixes at T0.

The ideal scenario is to apply Monolith (mesosulfuron + propoxycarbazone) and Atlantis (iodosulfuron + mesosulfuron), plus Biopower, in a separate pass to ensure maximum efficacy on grassweeds and crop safety. Remember to wait at least seven days after application before applying a T0.

If you must use these products in complex tank mixes, remember to avoid tebuconazole and chlorothalonil products. Also consider applying nitrogen before application to ensure the crop isn’t stressed, with a healthy crop helping to negate any crop safety issues.

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