Crop Crack

All T3 fungicide applications onto winter wheat should now be planned for application over the next week.  Winter wheat crops have moved at exceptional pace during the dry warm period over the last couple of weeks.  The cornerstone for the T3 head spray fungicide is a strong triazole that as well as being effective on Septoria is also effective on Fusarium.  Prothioconazole & epoxiconazole remain the most effective products to give ongoing Septoria protection.  Tebuconazole and metconazole are very strong triazoles for Fusarium and an important contributor at this time. The addition of a strobilurin is also essential to maximise the persistence of the triazole and strengthen activity on Yellow Rust.  Good grain fill is totally dependent on retaining green leaf area for as long as possible, and the addition of the strobilurin extends the retention of green leaf tissue.   Last years’ HGCA trials show pyraclostrobin (COMET) to be the highest rated strob for use in wheat being the strongest performer on Yellow rust and the late ear diseases. Products containing the active prothioconazole are in short supply this season and therefore an alternative choice may be required.  I have seen a lot of physiological tipping on winter wheat and there are a lot of theories as to what may have caused this but most noticeably it seems to be specific to certain varieties.   Mildew has been present on most cereal crops this season where the variety has low resistance a mildewicide must be included in the fungicide program.   All weed control should now have been carried out on spring barley crops and all should now have received the T1 fungicide application as rhyncho is present on most varieties. Concerto and Waggon both have a very low rating for rhyncho resistance.   The two most dominant diseases in our climate are powdery mildew and rhynchosporium with ramularia becoming an increasing problem over recent years.  Ramularia can be difficult to identify but unlike most other physiological leaf spots which are only visible on the upper side of the leaf ramularia is easily seen both on the upper and lower surface of the leaf and the longitudinal edges of the brown lesions remain enclosed by the leaf ridges. Symptoms appear where crops are subjected to stress from alternating periods of wet weather & sunshine, or man-made as a result of scorching.  Chlorothalonil (BRAVO) is very effective when used preventatively, helping to maintain green leaf area when used along with a triazole/strob mixture.   Where growth regulation has not been carried out it is critical to check crops and apply Cerone onto crops beyond GS32 if required.   Moddus can be used on crops which have not yet reached GS32.

All weed and disease control should now be complete on both spring wheat and oats.

Grassland

Attention must now be given to those grass fields which were not sprayed prior to first cut. Grassland herbicides use growth function to kill weeds, therefore peak growth periods should be used for herbicide application. There must be sufficient growth to allow herbicides to be effective and vegetive growth is the key time to apply, as the chemical then gets drawn down into the roots. Herbicides are less successful once plants have progressed to the reproductive stage and have thrown a stem or began to seed. Once weeds are beyond the ideal growth stage for spraying they should be mown or topped and allowed to regrow again, and a herbicide applied to the fresh young growth.

To optimise efficacy of any herbicide, recommended water volumes should be observed, even when it means more time spent spraying. It is important to note ragwort plants in their second year are now coming close to flower and should be sprayed immediately as flowering ragwort is poorly controlled. The routine herbicide treatments for this weed are full rate MCPA or 2, 4-D, and they are most active on growing rosettes with reduced activity as the stem starts to extend. They are not clover safe. You can use a mixture of both these products as Nufarm Lupo which allows an increased dose herbicide compared with either alone, with a consequent activity benefit.   Forefront T is the most effective herbicide on ragwort.

Stock must be kept off until the weeds have rotted away, which can take up to six weeks.

Potatoes

Where broad –leaved weed control has yet to be completed and the crop has passed the latest timing for Sencorex a reduced rate of Sencorex tank-mixed with Titus will provide a wider weed spectrum of weed control than Titus used alone and can be used on emerged crops up to 25cm high where the label allows .Scutch, other grasses or volunteer cereals are not controlled by the Titus/Sencorex mix. Where these weeds become a problem in coming weeks the graminicide Shogun can be used. Shogun can cause transient yellowing and is therefore not approved for use on seed crops.

As canopies close, the soil surface will tend to remain damper, encouraging slugs onto the soil surface. Timing is critical for effective control, just before the crop meets across the rows. Take advantage of any rainfall by applying pellets just afterwards, as this will bring slugs up onto the soil surface. Potato varieties particularly susceptible to slug damage include Maris Piper ,Desiree and Kerrs Pinks.

Blight fungicides move through the plant in three different ways contact, translaminar and systemic.  Dithane,Ranman Top, Shirlan and Tizca are all contact fungicides. These Products protect only the outer surface of the leaf onto which they are deposited.Translaminar products such as Curzate M, Invader, Resplend and Revus move into the leaf and redistribute throughout the leaf tissue as it increases in size whilst systemic products such as Consento, Fubol Gold  and infinito move in through the leaf surface and upwards into the new growth protecting this from infection also. Products that have zoospore activity are the most effective 1^st spray, applied at the rosette stage prior to rapid haulm growth. Shirlan or Tizca will control any zoospores that may be in the soil and provide good protection of the new plant.   During the main canopy development phase with the considerable amount of new growth it is essential the product being used is fully systemic to properly protect the new leaves being put on between applications. Later planted crops are higher risk as they produce more new growth between applications than earlier drilled crops, at a time when the level of inoculum in the air is progressively increasing. If spraying during periods of unsettled weather, rainfastness of all products will be further improved with the addition of a sticker to the spray solution. Guard is a latex sticker and will improve the retention of the fungicide onto leaf surface, so improving both adhesions onto the leaf immediately post application and over the following days should rainfall levels remain high. The way the blight product is applied is as important as the product choice. Make sure nozzle type used is correct to ensure sprayer pressure; droplet size and water applied is as directed on the label. Inspect and calibrate nozzles regularly to maintain performance.   Never use any blight product at reduced rates.  Do not spray when the leaves are wet as this will significantly increase the likelihood of runoff.

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 any 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. Options are ALLY MAX covering 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), OXYTRIL CM controlling (field-pansy, red dead-nettle and speedwells) and SPITFIRE /MINSTRELfor chickweed and cleavers.

Where the range of BLWs present are limited to chickweed, redshank, fat hen, fumitory & day nettle, the hormone mixture products 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-ureas 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 and i have been in crops with ears emerging last weekend.Septoria tritici is 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 will form the key part of the T2 fungicide onto winter wheat. Tri morpholine should be included azoles continue to form the backbone of all treatments but with their performance continuing to decline, 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. Growth regulator must also be applied at this time where required.

Most winter barley crops are now at flagleaf fully out to awns just visible. Because of the very poor growing conditions up until last week, this year more than ever nodes and crop height is not a good indicator alone of the plant growth stage. Due to the extremely wet winter conditions very poor roots were established and there is a real need for growth regulator. 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 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 continue to warm 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.