Crop Watch: Cereal disease and OSR fertiliser decisions

Plenty of disease is being reported in winter cereal crops, with septoria in early-drilled wheats in the South West and net blotch rife in northern winter barley crops.

In oilseed rape, decisions are being made on fertiliser strategies based on biomass, with rates knocked back for big, bulky early-drilled crops. 


David Martindale

Arable Alliance (Yorkshire)

An exceptionally dry start to 2023, along with spells of above-average temperatures, have made spring-like conditions arrive early. This has been good news for the sowing of spring crops, with good progress already made.

Seed-beds have been good too. Even some heavier soils have been drilled for some time now, which seems surreal. Autumn-sown crops are coming out of winter in good condition.

See also: Lincs grower tightens grip on top-yields record with new win

Many cereal crops look like they had already received 50-60 kg N/ha prior to receiving any nitrogen fertiliser. Good progress has been made with first nitrogen fertiliser applications to oilseed rape as well as cereals.

Oilseed rape crops have appeared quite ragged recently as older leaves have died back through natural senescence and frost effects, as well as larval damage from cabbage stem flea beetle (CSFB).

These effects have been more noticeable in earlier-sown crops where there was a larger canopy to lose leaves and greater CSFB larval numbers compared with those sown much later.

New growth so far looks good, although this can change if high numbers of CSFB larvae congregate in the main stem, where the damage can be severe.

Light leaf spot is now appearing and fungicides are being applied to more susceptible varieties.

From 1 March any remaining weeds such as thistles, mayweed and cranesbill can be controlled with herbicides such as clopyralid with or without halauxifen-methyl. The cut-off timing for these herbicides can be quite tight on very advanced crops, so it is worth checking crop growth stage before spraying.

OSR fertiliser

Earlier-sown crops already have a green area index (GAI) of well over 2, which is a considerable biomass for the time of year. These crops will shortly receive a plant growth regulator to reduce their final height.

However, delaying the first dose of nitrogen has a much more significant effect in managing canopy height, so some gentle persuasion to keep the fertiliser spreader out of the field has been required in some cases.

Early-sown wheat crops look particularly well. The mild autumn has allowed additional tiller formation, so these crops look quite frothy at the moment. Starving these thick crops of nitrogen is necessary in order to keep shoot populations to a manageable level and prevent lodging. Otherwise, most wheat crops have now received their first dose of nitrogen fertiliser.

Yellow rust is visible in some crops. However, infection levels at present are relatively low compared with recent years. Even the higher-risk coastal areas are not too badly affected so far.

In contrast, there is a lot of Septoria tritici on the older leaves so if the spring proves to be wet there is plenty of inoculum already present to splash up the canopy.

Contact-acting herbicides for grassweeds such as ryegrass and bromes will be applied as soon as temperatures have risen sufficiently.

Winter barley crops look particularly well, having hardly lost their green colour this winter. These crops seem to be carrying higher levels of disease compared with winter wheat. Net blotch is particularly rife, with brown rust levels also high in susceptible varieties.

The first dose of nitrogen fertiliser has been applied to winter barley crops in order to maintain tiller numbers and maximise yield potential.


Neil Potts

Matford Arable (Devon)

We saw a very wet spell in November and December which meant any field work, including spraying for barley yellow dwarf virus, was largely impossible. The wet episodes were broken by a very cold snap in early to mid-December and another one, accompanied by snow, in January.

Early planted forward crops suffered a bit in the snowy cold spell as growth was pushed down onto the ground, where patches have subsequently been frosted and then rotted. Apart from this, though, crops on the whole have come through the winter looking very well and carrying more biomass than usual.

Despite the cold spells, winter has been a fairly mild affair for the deep South West. This has created the larger-than-usual crops, in turn leading to many crops having some fairly ugly levels of foliar diseases.

Septoria is rife in earlier-drilled crops, with little difference between resistant and less-resistant varieties at this stage. Winter barley crops are carrying levels of all four major foliar diseases: rhynchosporium, net blotch, mildew and, in pockets, brown rust.

Oat disease

Winter oat crops have high levels of Septoria avenae while mildew and crown rust are not difficult to find. I know it is early, but unless we have a long dry period going into late March and April the season is shaping up to be very challenging from a disease control point of view.

On the plus side, large biomass crops have plenty of potential to yield well if managed properly.

Oilseed rape crops have done what they usually do over winter and shed biomass as lower leaves die back and the frost, snow and, in places, pigeons have all had their part to play as well.

Nitrogen management is going to be interesting, with most growers having bought at high prices and current crop values below where they need to be. The forward bulky crops coming out of winter have at least trapped a fair amount of N from the soil, so we will not be looking to apply large amounts to build biomass in all crops.

On the other hand, adequate N will need to be applied fairly early to ensure that we keep these larger crops going. The last thing we want to see now is crops shedding tillers which have taken energy to grow.

Should the season turn out to be a bad one for foliar diseases, supply chain issues are bound to be a bit of a problem, with most manufacturers producing finite amounts of fungicide, based largely on last year’s usage. Last year was hot and dry, so by no means a bad disease year.

There is plenty of potential out there at the moment. Let’s hope we are all able to realise it and that something comes along to help nudge grain prices in the right direction. 


Tod Hunnisett

AICC (Sussex)

It’s the last week in February and we haven’t had any real rain for at least three weeks. People have started drilling spring barley, which is going in under very good conditions.

We haven’t even had prices for pre-emergence treatments yet. I do wonder if we are in for a long spell of wet weather, as it seems that’s the way the weather patterns run these days. The tabloid-promised Beast from the East has not yet materialised, so for that we can be thankful.

Winter drilled cereals, generally speaking, look absolutely fantastic, with autumn herbicides having done a superb job.

I have a couple of very late drilled crops (both second wheats) that have not enjoyed the alternating very wet followed by very cold weather.

OSR looking good

Most oilseed rape looks happy. Ironically, some of those drilled into bone-dry seed-beds look the best.

I don’t bother looking for flea-beetle larvae these days. There’s nothing I can do about them anyway, and they never seem to correlate to yield effect provided there are enough plants surviving to make a crop.

Some of the worst-infected fields I have seen in the past have gone on to produce good yields, and vice-versa.

It’s too cold to be thinking of spring grassweed applications just yet. The weeds need to be actively growing to get the best out of contact-type herbicides.

Very often the reason why they don’t work is not because of resistance – they just haven’t gone on in the right conditions.

If the kind weather continues, people will be itching to go on with other spring crops. Peas and beans can be drilled early if they go into good conditions, but if the ground is puggy then patience is a virtue.

And nobody should be thinking of drilling linseed or spring OSR until the weather is much warmer – they have to get up and away straight after drilling.

Tractor and trailed drill drilling spring wheat

© Tim Scrivener


Ben Pledger

Farmacy (Bedfordshire/Hertfordshire)

A dry spell towards the end of January saw the start of nitrogen fertiliser application to most autumn-sown crops.

With the greater reliance on urea this year, earlier applications than deemed usual have allowed for the extra time taken for the product to become available to the crop, and indeed it is now evident that this has been taken up and is now being used.

Oilseed rape in particular – where it has made it through the CSFB larvae and heavy frosts – has started to grow away from the later-than-usual bombardment by pigeons.

Even after what seemed to be a decent wet spell over the winter, soils are still dry at depth.

Soil structure in most places is still in good order after the very dry summer, and this is evident if you look at the speed soils dry out after a rain event.

With parts of France and Italy declaring drought conditions this early in the year, the mind is focused again on getting the best from our crops with potentially less-than-ideal soil moisture this spring.


Getting root systems well established and working for us will be key to getting the best possible take-up of nutrition. Tissue testing will also be carried out through the spring, with deficiencies corrected by applications of foliar nutrition.

Frost lift has been widespread, and spring rolling of autumn-drilled cereals has already started to ensure good root-to-soil contact.

Phosphite will be applied where rooting is poorer to encourage root growth, along with trinexapac-ethyl once growth stages allow. This will also reduce the risk of root-based lodging.

Spring drilling is under way, albeit in some cases earlier than the textbooks would suggest, regarding the fight against blackgrass.

Where spring barley is being drilled for blackgrass reasons, variable seed rates are being used to increase seed rates and so competition in areas with higher blackgrass populations.

Where soil moisture is present in blackgrass situations, diflufenican, flufenacet and pendimethalin will be applied pre-emergence.

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