Crop Watch: Disease lurks at base of cereal canopies

Cold and wet conditions are prohibiting growers getting into fields on all but the lightest land, but that shouldn’t stop preparations being made for the imminent growing season.

That’s why our Crop Watch team are back to offer their pointers on how to get the most from your spring and autumn crops and tackle weeds and diseases wherever they rear their ugly head.

North: Mary Munro, AICC/Strutt & Parker (Perthshire)

Mary MunroNorth of the border we are still in the grip of winter, meaning there is little to report in the way of crop development. The bonus is the impact of wintry conditions on crop pests and diseases.

Winter barley and more forward wheat crops were carrying significant amounts of mildew into the winter but this will have died in the cold, as mildew needs at least 5C to be active.

Some oilseed rape crops are suffering from pigeon damage and light leaf spot, which is normal for this time of year.

Most fields are very wet, and fertiliser application is not yet a matter of debate. There has been a bit of ploughing done this month, but not a great deal of activity.

Cover crops showing value

More growers have tried the Green Cover option for Ecological Focus Areas this season. Many were established at the last moment after a drawn-out harvest, and some looked singularly unimpressive at first.

These are now doing a decent job of providing cover and will be ploughed in prior to spring crop establishment, giving soil organic matter a boost.

This is a good option for the all-arable farmers who don’t have ready access to farmyard manure.

There is a great deal of interest in methods to revive soil health just now and people are burying underpants all over the place to monitor microbial activity.

All soil aspects need to be considered together otherwise progress will be slow – chemistry, biology, and physical structure are inextricably linked.

The basics are not so difficult – soil analysis and correction of nutrient deficiencies; crop rotation, appropriate subsoiling and the return of organic matter; effective drainage and the avoidance of heavy traffic on wet ground will all help make a better environment for earthworms and the other less-visible life that should be there.

South: Richard Harding, Procam, (Sussex)

Richard HardingAs often happens in February, just when you start to think spring is arriving, winter returns.

Ground conditions on the Downs are drying but still fairly wet. We are also experiencing regular hard frosts and you can almost sense the temptation to start applying fertiliser.

It is good agronomic practice not to apply manufactured fertiliser or other nitrogen-containing materials if the soil is waterlogged, flooded, snow covered or frozen for more than 12 hours in the previous 24 hours.

These are part of cross-compliance rules, as is not spreading manufactured fertiliser within 2m of surface water.

You should also not apply if heavy rain is falling, or forecast to fall within 48 hours. Application is allowed on days when early morning frost thaws during that day.

Generally, crops have wintered well and, apart from waterlogged areas, are in good condition and not urgently needing nitrogen – and will not make much use of it anyway until soil temperatures are above 5-6C.

Disease seen in wheat

To date, it is possible to find bottom leaves of some wheat varieties like Lilli showing rust, mildew and septoria but the temperatures of last week might help to supress disease.

Rapeseed crops have come through the winter clean of disease and – not wanting to tempt fate – fairly free of pigeons at the moment.

The main focus for field work so far this year has been spring ploughing where conditions allow, and grazing or spraying off cover crops in readiness for spring drilling.

Deciding whether to direct drill spring crops on the green is always a much-debated topic, and the correct decision is affected by many factors, and generally best decided with hindsight.

In no-till situations, spring oats look like a good fit, and a possible replacement for spring barley, performance of which can be variable when direct drilled in the spring.

West: Antony Wade, Hillhampton Technical Services (Herefordshire/Shropshire)

antony wadeEarly drilled wheat crops have tillered well, I have September-drilled crops with 8-10 tillers with strong leaf area, and we may even lightly sheep graze some of the strongest crops.

The autumn mildew that was prevalent in some of these crops (especially Leeds and Revelation) has browned and looks inactive after frosts but will soon liven up with milder temperatures.

In recent field inspections septoria is becoming evident on lower leaves, and is particularly noticeable on varieties such as Siskin, as a result of the regular rainfall we have had through December and January.

I have yet to see any yellow rust, although I have generally resistant varieties planted – if any can be said to be resistant with current fast-evolving races.

Bigger crops, bigger yield

Data from the YEN conference revealed the only correlation to the highest-yield entries is large biomass crops, so I am hopeful that we have started the season with good potential.

On a couple of my farms that have YEN entries we intend to monitor shoot/ear numbers through the season as I am convinced that the current benchmarked references used are not correct for modern high-yielding varieties.

Other cereals are similarly well set-up. Hybrid and conventional winter barleys have tillered equally well, although leaf area has just started to yellow, so will be first to get nitrogen once we can travel.

The thickest oats are carrying quite a bit of mildew, which will probably need an early spring mildewicide.

Triticale is looking strong, so will require a robust growth regulation strategy, even on the crops that are destined for the anaerobic digester, as they have the potential to lodge.

Oilseed rape is the only crop that I am not so content with looking large, as we know thick crops do not produce the best yields.

Most crops had autumn tebuconazole to hold them back, but although canopies reduced over winter they still have a green area index of 1.5-2 so Caryx (mepiquat + metconazole) is planned for many.

East: Marion Self, Prime Agriculture (Suffolk)

marion self

Very little spring drilling has taken place (too cold and wet) and anyone seizing an opportunity should adapt the seed rate to the field conditions.

Early and later drilled winter cereals have tillered well, appearing healthy with good yield potential.

Cereals are “tinged” by the cold temperatures and wind, with some showing early manganese deficiency symptoms.

Rust and septoria levels are relatively low, although lesions are easily found. Mildew levels have been moderate since autumn, but recent frosts have held the disease.  

Beans look well but some crops may still require a follow up grassweed spray with carbetamide. On wet fields this may be difficult to achieve before the 28 February deadline.

Pigeons assault oilseed rape

Rapeseed is now looking beleaguered by the weather and hungry pigeons. Crops have good root systems and will grow away quickly when the warmer weather arrives and the first nitrogen and sulphur fertilisers are applied towards the end of February.

Some crops will require additional fungicide for late light leaf spot infections and larger canopies will require growth regulation at green bud.

Those in favour of canopy management will be looking to adjust the first N dose according to the Green Area Index (GAI); this gets problematic when pigeons defoliate crops. 

Crops have a range of GAI’s between 1 and 2.5, so care should be taken if adjusting N dose and when selecting the appropriate PGR treatment.

The BASF app can quickly identify the GAI if you are unsure or need calibrating. Cabbage stem flea beetle are easily found in the leaf petioles, although larvae in the main stems are harder to find.

Remember that good seedbeds are often more important than calendar date. It may be some time before some fields are dry enough for action. Now is time to field walk, complete nitrogen and sulphur plans and firm up the spring spray strategies.

Tip of the Week

Avoid relying on green area index alone when assessing how forward oilseed rape crops are if they have suffered significant pigeon damageMarion Self

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