Crop Crack

The mixed weather and below average temperatures have certainly made things difficult for both arable and grassland farmers recently. We have almost accepted there is no such thing as the norm anymore. It has been very frustrating for farmers trying to grab every available opportunity to spray crop as ground underfoot has become very soft. Conditions however have been ideal for weed control onto potatoes and veg as residual herbicides require moisture to work effectively.

SPRING CEREALS

The above average rainfall over winter has depleted many soils and it is essential to replace essential nutrients. Spring barley crops grown on low PH soils with a low P index seem to be struggling most this season. This must be rectified with lime and Phosphate fertilizer in accordance with soil analysis.

An application of a balanced and rapidly available source of macro & micronutrients at this key time will minimise the adverse effects of restricted soil nutrient uptake. CEREAL HIGH N supplies 3.7%Mn, 1.5%Mg, 1.8%Cu, and 0.6% Zn in the most rapidly available form to the plant through the leaf and also supplies high levels of Nitrogen and Sulphur.Potash deficiency is also showing up in many spring barley crops with pale green yellow tips being the first symptom.Deficency is most likely on light sandy soils or in crops following intensive grassland. Manganese deficiency is also appearing on crops especially those in a continuous cereal regime or where lime has been applied recently. A foliar application may be applied along with the weed control.

To minimise the effects of competition on the crop and optimise the level of weed-control, herbicide application should be carried out at the earliest opportunity, once all the weeds have emerged but are still small, and before they begin to compete with the crop for nutrients and light. With low soil temperatures since drilling, weeds are not coming through as rapidly as expected but chickweed is beginning to choke out young plants and must be sprayed as soon as possible.

Product choice will depend on the weed type and size present and the crop growth stage. Broad leaved wise, Sulfonyl-urea (SU) herbicides will likely be the starting point, controlling a wide range of weeds and very safe to the crop. ALLY MAX covers a wide spectrum of BLW with the max formulation giving improved control of polygonums & other BLW over the old ALLY formulation. HARMONY SX controls a wide range of BLW at sizes larger than any other SU. However they must always be tank-mixed with another BLW herbicide to control SU resistant weeds (chickweed) and those weeds not controlled by the SU’s (cleavers, fumitory& fat-hen). Ideal partners are COMPITOX controlling (chickweed, fat-hen, fumitory), and SPITFIRE /MINSTREL for chickweed and cleavers. HUSSAR may be applied to spring wheat and spring barley to help control annual meadow grass.

Where the range of BLWs present are limited to chickweed, redshank, fat hen, fumitory & day nettle, the hormone mixture products, such as Mircam Ultra, will work well without the need to tank-mix, but must be applied by GS31. Where the likes of field pansy, forget-me-not, speedwells & corn-marigold are also present, sulphonyl-urea products will improve control.  AXIAL gives excellent control of wild and tame oats in spring barley and spring wheat and has an excellent window of opportunity.   Application should be held off until at least 6 weeks after drilling to ensure all wild oats have germinated. It can then be applied up to full flag-leaf of the crop and full flag leaf of the wild oatGS39, allowing a minimum of 21 days to have elapsed after application of the BLW herbicide.  The wetter ADIGOR must be used in all situations along with the AXIAL.

WINTER WHEAT

Most crops are now at flag leaf with Septoria tritici present in most crops at variable levels depending on T1 timing but with recent weather expect levels to rise if fungicide rates and timings are not correct. Mildew is present on almost all winter wheat varieties and a morpholine based product should be applied to clean up the crop. The inclusion of Talius in the program will give very good persistent control of mildew. Of all fungicide treatments, T2 has the greatest impact and response in terms of grain yield and quality, keeping the top three leaves clean and the ear as it emerges. The dose rate applied must be sufficiently robust to ensure long term protection of the flag leaf plus eradicate disease already present on the lower two leaves that also contribute to yield. Epoxiconazole & metconazole in mixture(BRUTUS) will form the key part of the T2 fungicide onto winter wheat.  SDHIs are now regarded as essential partners to maximise the yield of all crops with any reasonable potential, with the most responsive timing for the newest SDHI molecules being at T2. Products such as PEXAN or AYLORA/PROSARO mixtures are ideal for use at the T2 timing. Growth regulator (CERONE)must also be applied at this time where required.

The last fortnight has offered very little spray opportunity but every available chance must be taken to ensure correct spray timings. Most winter barley crops are now at flagleaf fully out to awns just visible. Because of the very poor growing conditions this spring, nodes and crop height is not a good indicator alone of the plant growth stage. Growth stages in cereals are hugely influenced by day length. The longer days are driving ear development, and with it ear emergence.

In winter wheat the weakest part of the stem tends to be the lowest internodes and therefore growth regulation at this time maximises strengthening, in barley it is the higher internodes that are weakest. In winter barley the SELON growth regulator applied some weeks ago enhances root anchorage and tiller survival, but has little effect on controlling stem lodging. It is during the later stem extension stages and early flag leaf emergence that the maximum straw strengthening effect will be achieved. When the application is delayed beyond this timing efficacy drops off rapidly, as with each passing day the stem has already added on further length. In any event it is essential the growth regulator is applied before the awns start to appear – a late application as the awns are emerging can damage the emerging ear. The T2 fungicide program should now be planned for winter barley. Properly protecting the top three leaves and ear at T2 is critical to yield and profit – up to 80% of the yield is generated from these leaves. Foliar disease not controlled effectively at this time will hasten the senescence of these leaves during grain filling, and therefore compromise yield and grain quality. Yet there is little point in applying any input if it does not give a financial return. To get the best return on fungicides, applying them at the correct timing is critical.

Spring Cereals

To minimise the effects of competition on the crop and optimise the level of weed control, herbicide application should be carried out once all weeds have emerged but are still small, and before they begin to compete with the crop for nutrients and light. Carrying out the weed control at the 2-4 leaf stage is much more effective especially on difficult weeds such as fumitory and knotgrass, rather than delaying to coincide with the 1^st fungicide application.

Broad leaved weeds resistant to certain herbicides in NI is not a new problem – continuous use of straight metsulfuron (ALLY) in previous years has resulted in strains of chickweed that are no longer controlled by this chemistry. Sulfonyl urea (SU) herbicides such as metsulfuron have a single mode of activity, blocking the production in many BLW of a key enzyme, acetolactate synthase. Products that use this mode of activity are known as ALS inhibiting herbicides and include the SU chemistry. ALS resistance is becoming a bigger problem with other weeds now developing this type of resistance, including mayweed and poppy. This development seems inevitable following the continued use of products with the same single mode of action, and more than ever mixtures of products with different modes of activity are essential to maintain good weed control. ALS inhibiting herbicides must therefore always be tank-mixed with another non ALS herbicide to ensure satisfactory weed control, especially of chickweed in NI.

Leatherjackets

Leatherjacket numbers are very high this year with widespread damage seen in recent weeks to new leys and established grass swards particularly in the west of the province. Damage will become evident as spring crops emerge, leaves and whole plants yellowing, cut off just below ground level. Crow activity is also a sure sign of leatherjackets being active. Crops most at risk are those drilled into old ley or dirty stubble, but monitor all emerging crops closely for signs damage. Feeding activity and therefore the likelihood of damage will increase as soils warm up as the leatherjacket continues to feed for some weeks yet before hatching out in late May / early June.

Growth Manipulation

Since tillers are a critical component of yield and tiller numbers decline the later the crop is drilled, it is important that these crops be encouraged to tiller to improve yield potential. Because of the more rapid progression through the growth stages than the winter crop, the growth regulator must be applied very early to maximise the suppression of the main stem development (apical dominance) and therefore divert nutrients and growth to promote tiller development. Optimum timing for barley is from the 2 expanded leaf stage to beginning of tillering, GS12–21; in wheat the optimum timing is slightly later, 5 leaf to mid tillering, GS15-24. SELON is the only chlormequat product approved for use on spring barley. Because an early application suppresses the main stem development and so diverts the growing efforts to the tillers, this extra growing effort also increases root development in the plant, improving crop establishment, stem base lodging (not brackling) and yield. This treatment also gives a consistent straw shortening effect in wheat, but not in barley.

Horticulture

The recent frost has had serious implications on many of our horticultural crops especially the apple and early potato crop.SEAMAXX is a seaweed based fertiliser that can help improve resistance to environmental stress such as extreme temperature, wind damage and drought. It helps the orchard to maintain growth during hostile growing conditions, by reducing stress there is more energy available for flowering and fruit set leading to improved yields. At this critical time MACANNI should be applied as it is safe through the blossom.

With temperatures rising, days getting longer and top dressings kicking in, crops are starting to come away, especially those on drier soils. Soil temperatures have not dropped as low as usual with the milder winter and therefore the early start to growth comes as no surprise and is encouraging in terms of building yield. Leather jacket numbers remain high and all crops should be monitored closely. Now is the time to spray autumn reseeds to ensure weed competition does not choke out the young grass.

Winter Barley GS30 – GS31

All crops have completed tillering, with the most forward fields past 1^st 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 poor seedbeds, waterlogging, slug and leatherjacket damage. As temperatures rise slugs and leatherjackets are still a threat to more backward crops and should be treated if any new damage is seen. 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 NI. 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 then right through to crop senescence.

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 have 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 1^st and 2^nd node, GS31-32.

Holding the T1 timing to GS31-32 should ensure T2 in barley and T2 & 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) has proven to the most effective performer on both Septoria and Ryncho. Boscalid (in WHISTLE or KINGDOM) 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 1^st–2^nd 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

While most crops received a herbicide treatment in the autumn, 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 into the spring, 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 1^st 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 1^st-2^nd 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 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.