‘Growth is not what we expect’

The winter barley harvest gets underway in ideal weather conditions at Barclay Bell's farm near Rathfriland. Picture: Cliff Donaldson
The winter barley harvest gets underway in ideal weather conditions at Barclay Bell's farm near Rathfriland. Picture: Cliff Donaldson

Growth is not what we would expect for the middle of April, and it is important to note that stress in whichever form will affect nitrogen utilisation.

Nevertheless top dressings are kicking in and crops are starting to come away.

The poor economics across the agri-sector coupled with the persistent bad weather conditions have left a very depressive mood amongst many of the farmers I have been speaking to in recent weeks.

Winter Barley GS30 – GS31

All crops have completed tillering, with the most forward fields past 1st node, GS31. Most are looking well considering the wet conditions over the winter.

There are good plant counts and tiller numbers, but the mild winter means disease is already well established on these young plants with Rhyncho, mildew and net blotch showing in all. Rhyncho remains the most damaging disease of barley, seriously damaging yield potential if not controlled quickly and effectively.

Winter Wheat GS22 – GS30

Growth stages vary widely depending on drilling date but most are at various stages of tillering.

Most have good plant numbers but some fields have suffered from waterlogging, slug, leatherjacket and rabbit damage.

Septoria is established in all crops but particularly so in earlier drilled fields.

Disease Control

Rhynchosporium and Septoria are the two most damaging cereal diseases in Northern Ireland.

Both have always been more effectively controlled protectantly, but in previous times where the curative properties of the azoles were able to rescue a bad situation later, particularly in wheat this is no longer the case.

Growers must now change their approach, looking to keep ahead of both diseases by starting earlier than before and maximising the protectant activity of the chemistry available.

Timing of fungicide applications and rates used are every bit as critical as product choice to achieve the maximum potential response.

To ensure the main disease programme persists right through to ripening, it is adviseable that all crops should have by now received a T0 fungicide.

Farmers should not apply their main T1 fungicide application before about the middle of April, with the T2 and T3 applications following at 4-5week intervals, ie mid-May and mid-June.

This T1 timing should coincide with the beginning of stem extension between 1st and 2nd node, GS31-32.

Holding the T1 timing to GS31-32 should ensure T2 in barley and T2 and T3 in wheat be optimally timed to avoid extended gaps, maintaining persistency right up to and during senescence.

Where a crop has not received a T0 treatment product rates at T1 will need to be increased to take account of this.

Since their introduction, fungicide programmes containing SDHIs, or succinate dehydrogenase inhibitors have consistently out-performed triazole only programmes.

These are the newest family of chemistry available to cereal growers and now considered the mainstay of disease control programmes.

They work by inhibiting fungal respiration and are more effective at controlling a range of diseases than older products, particularly as the performance of triazoles continue to decline each year.

However SDHIs only have this single mode of action and therefore resistance and the associated breakdown in control is a very real threat to these products.

To try and prevent resistance building up against the SDHIs, they must be used only twice in a season and in conjunction with another fungicide, such as a triazole, with a different mode of action.

Of the SDHI products available, penthiopyrad (in AYLORA/CIELEX) has proven to be the most effective performer on both Septoria and Ryncho.

Boscalid (CHORD) remains the strongest active available to control Eyespot and therefore a very good option for use on wheat at T1.

CONCORDE containing isopyrazam and cyprodinil will be widely used as T1 on barley this season.

This is an SDHI mixture proving to be very strong on both eyespot and ryncho.

The T1 treatment in oats should be applied at the same time as the growth regulator.

Whilst traditionally a single fungicide program was often used on this crop, a 2-spray program consistently outperforms a single spray in terms of yield, bushel-weight and profitability.

CAPALO is the strongest T1 treatment available in oats, giving excellent curative activity on Crown Rust and Mildew when applied at 1st–2nd node (GS31-32), and is very persistent keeping new growth clean right up to full flag leaf (GS39) when the T2 is applied.

Weed control

Many crops have received an autumn herbicide but for those still to be treated, control of Annual Meadow Grass (AMG) is the most pressing issue.

OTHELLO is an excellent option for AMG in wheat, however there is no similar late option for barley.

Note that OTHELLO will only control AMG that has already emerged; unlike the autumn products it has no pre-emergent activity.

Where the AMG has been controlled in the autumn but for example chickweed, cleavers or groundsel is likely to be a problem, SPITFIRE is an excellent stand-alone broad spectrum herbicide controlling these and most other emerged BLW.

It also works best when the weeds are growing actively and has post em activity only, therefore delay use until all cleavers have germinated and temperatures have risen to encourage growth.

SPITFIRE is also an excellent tank-mix partner with OTHELLO.

Growth regulation

When applied before 1st node, GS31, application of certain chlormequat growth regulators can significantly increase tiller numbers. Chlormequat works by suppressing apical dominance, ie main stem development.

In doing so it diverts the plant’s resources into producing and supporting more tillers.

Particularly in wheat but in barley also, more tillers will go a long way towards compensating for low plant counts, ultimately increasing yield.

Correct timing is critical to maximise this effect.

The earlier it is applied during tillering the greater the tiller effect, but note early application to increase tiller numbers will also reduce its effect on lodging.

Application of a chlormequat based growth regulator often goes on with a T1 fungicide application sometime around 1st-2nd node, GS31-32.

At this timing it is too late to affect tiller numbers and survival but will maximise the stem stiffening effect.

Early application will also increase root growth and so reduce stem-base lodging.

Stem-base lodging is where the plant folds over at the soil surface as a result of poor anchorage in the soil, and is caused by poor root ball development, more likely when the seedling develops in wet soils that limit root development.

All winter crops have rooted very shallow this season as a result of the persistently wet conditions and therefore stem-base lodging is likely to be a significant problem later this season.

SELON can be tank-mixed with the herbicide and where the crop has begun to tiller, should be applied now.

Nutrient Deficiency

A combination of waterlogged soils, plants already suffering from restricted nutrient uptake and plants now trying to grow is showing up Mn deficiency in many barley crops.

Continuous cereal ground and ground recently limed is most prone to deficiency.

Symptoms begin with small pale green speckles appearing throughout the leaf and these will progress to turn brown unless treated.

As soon as the ground allows, Mn deficiency should be addressed and applied as soon as possible along with the SELON application to increase tiller numbers.

Copper deficiency often accompanies Mn deficiency – its symptoms are complete browning of the leaf tip especially the youngest leaves, and apparent wilting of the plant.

Treatment will be most effective if treated immediately symptoms are seen.

With air quality significantly improving over the last two decades, the most important source of sulphur to the soil coming from the pollutant gas sulphur dioxide has also reduced significantly.

Whilst its deficiency is now being recognised and corrected on grassland through the application of high sulphur compound fertilisers, its impact in cereal crops in NI has by and large been misidentified or overlooked.

After nitrogen, phosphate and potash, sulphur is the next most important element required by all crops, used to make essential sulphur containing amino acids and proteins in all plants.

Soil sulphur is easily leached especially from light to medium soils, making shallow-rooting plants particularly vulnerable to deficiency.

Deficiency causes paling in the cereal plant, caused by a reduction in chlorophyll production and even in the absence of any symptoms, decreased efficiency of nitrogen utilisation.

Whilst often mistaken for lack of nitrogen, sulphur is not very mobile within the crop and therefore deficiency is most pronounced on the younger leaves; the opposite to nitrogen deficiency which affects the oldest leaves first.

Crops of both wheat and barley with high yield potential are particularly responsive to one to two applications of foliar sulphur at the timings of rapid growth.