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All weed control should now be almost complete on spring cereal crops. There was certainly plenty of opportunity to catch up on spray programmes over the last couple of weeks. Crops are moving through the growth stages very quickly this week with the damper conditions. Some spring barley in parts of North Down are already at flag leaf and East Down have crops with awns appearing. Wild oats may be controlled now as long as a period of three weeks has occurred from the weed spray application. Axial and Adigor may be used on both spring barley and spring wheat up to flag leaf. It is certainly a season where growth regulator will be required in abundance. As most crops are now past 2nd node growth regulation products are limited to Cerone for barley up to first awns visible and Adjust and Cerone on to spring wheat up until flag leaf sheath opening. Fungicide application is priority now as rynchosporium is spread by rain splash. This disease has been present in low levels up until now with netblotch being the most dominant disease in spring barley. Whatever the fungicide choice for spring wheat it is critical to include something to cover mildew as most varieties have mildew present on them.

Winter Cereals

Protecting the top three leaves 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 affecting 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. Trial work in UK & ROI has consistently shown even in a low disease pressure year, a well-timed application will give returns of 2-4 times their cost and in high pressure situations 5-6 times their cost. In winter barley this should be applied from the end of booting through to awns fully emerged, GS45-59, and be robust enough to protect the upper leaves and ear through to the end of the season. Awns also contribute to yield and it is important to keep them free of disease also.
For winter wheat the T2 should ideally be applied between mid flag leaf to mid-booting, GS38-45 along with the growth regulator. The T3 treatment is then applied post ear emergence to mid flowering, GS59-65, targeting ear diseases and prolonging control of foliar disease on the top two leaves, especially important in wetter seasons and on susceptible varieties.Sumi-alpha should be applied along with the fungicide.

Potatoes

Much of the potato crop this season has gone into cold soils and therefore drills are only warming up now. Both weeds and potatoes have been slow to emerge to date. Most weed control programmes are based on residual products ie products that are taken up through the soil, and are therefore very dependent on sufficient soil moisture to work effectively. Soil conditions are ideal therefore at the moment, moist enough on the tops of the drills to allow the herbicide be taken into the soil and taken up by the germinating weeds.
A huge amount of SAC work suggests that growers should spray before crop emergence to moist clod-free ridges. Holding off until crop emergence will set the potatoes back significantly reducing final canopy cover, and compromise weed control especially if weather delays the application further. The weeds are best treated pre or very early post emergent, especially important on the difficult weeds; fumitory, knotgrass, bindweed, annual meadow grass.
The key message is to apply the herbicide combination before crop emergence, therefore avoiding any check to the crop once emerged and maximising range of weeds controlled.
It is Tuesday today as I write this article and the steam is rising up from the road as I look outside. This certainly has been the first day since potato planting I could say there is a risk of blight. During the early canopy development phase, emergence to rosette products that have zoospore activity are the most effective 1st spray. RANMAN, SHIRLAN or TIZCA will control any zoospores that may be in the soil (either from ground-keepers or infected seed) and provide good protection of the new plant.

Grassland

With farms being short of grazing because of the cold conditions it is important to minimize the effects of encroaching perennial weeds. When targeting nuisance perennial weeds such as docks, nettles and thistles it is important to apply herbicides when the plants are actively growing and at the correct growth stage.
Most herbicide applications to silage ground occur prior to or just after first-cut. Depending on cutting date, the quality and quantity of silage taken will vary, placing greater importance on achieving the best second-cut possible.
Perennial weeds such as docks can significantly affect both the quantity and quality of grass harvested, so well-timed herbicide applications after first cut can reap rewards for the rest of the season and even into the next spring. This is likely to be particularly so this year with recent rainfall in helping to stimulate weed growth. To optimize results, wait for 2-3 weeks after cutting for docks to regrow to the rosette stage, and then apply DOXSTAR to actively growing plants. Doxstar has been developed to deliver the highest levels of dock control. The formulation and the presence of two actives; fluroxypyr and triclopyr, delivers a significantly higher level of control than straight fluroxypyr.

Good levels of weed control can also be achieved in grazing leys at this time of year. Where mixed weed populations are present, including docks, nettles and thistles, PASTOR is the most appropriate product to use. With the dry spring limiting grass growth, stock will have to graze closer to thistles leaving sheep vulnerable to orf. Getting rid of thistles in sheep pasture with THISTLEX significantly reduces the spread of orf while increasing grassland productivity.

FOREFRONT may be applied onto grazing ground giving excellent weed control with no effect on the grass. FOREFRONT contains Fluroxypyr and aminopyralid. As well as controlling docks it will control chickweed, buttercup, dandelion, nettle and thistle.
Treat weeds at the rosette stage, when they are actively growing. If stem extension is already occurring, use a mechanical topper first, and then treat regrowth when it reaches the correct stage.

The prolonged period of cold weather over recent weeks had restricted growth of all spring crops sown in late March. Whilst all germinated well, growth of most crops had been particularly slow. Rainfall has been adequate, enough to maintain good soil moisture ensuring even germination of crop and weeds, and not too much to cause any transient yellowing associated with plants struggling to take up nutrients in waterlogged soils.

The problem was very much the lack of heat, restricting nutrient availability and therefore growth and development. The pleasant rise in temperature this week has encouraged both weeds and crops to move rapidly. To date aphids have been discouraged from flying due to cool conditions but this will have changed this week with the sudden increase in temperature.

The well below average air temperatures up until now mean soil temperatures have also been well below average for the time of year. The Nitrogen mineralisation process in the soil where fertiliser nitrogen is converted to a form that can be taken up by the crop is a soil microbe process and therefore dependant on soil temperature. Hence colder soil has slowed the availability of nitrogen to the crop, and many other nutrients also, particularly manganese. Many crops are beginning to show nutrient deficiencies as a result.

The application of a broad-spectrum trace-element mix along with key macronutrients at this time is a very useful and beneficial way to supplement the plant’s nutrient requirements during periods of restricted availability, especially when coinciding with phases of rapid growth ie. during tillering and as stem extension begins. An application of a balanced and readily available source of macro & micronutrients that is not dependant on soil availability at this key time will minimise the adverse effects of restricted soil nutrient uptake.

Spring Cereals

To minimise the effects of competition on the crop and optimise the level of weed-control, the herbicide application should be carried out sooner rather than later, once all the 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 will lower rates of herbicide and give a much more effective result than delaying to coincide with the 1^st fungicide application.

Product choice depends on the weed type and size present and crop growth stage.

Broad leaved wise, Sulfonyl-urea (SU) herbicides will likely be the starting point, controlling a wide range of weeds and are very safe to the crop.

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 however, sulphonyl-ureas products will improve control. Conditions over the last week have been ideal for hormone products with consistent day and night temperatures. Compitox, Minstrel and Oxytril are the most widely used tank mix partners with SU’s.

Grass weeds are commonplace this season especially on head rigs, HUSSAR is the only product now available to treat AMG in spring crops, controlling it up to the end of tillering. It also gives very useful suppression of wild oats that are emerged at the time of application (further plants are likely to emerge later). It also controls a range of BLW very similar to the other SU’s.

If clover is part of the mixture, a clover safe product must be used. TRIAD is a new clover-safe herbicide available for the first time last season. Whilst currently labelled for use in ‘Spring Barley undersown with IRG’ only, a new wider label is currently going through the approval process reading ‘Spring Barley undersown with grass, and grassland’. If seedling docks, thistles and buttercup are also problem weeds, SPRUCE must be added to the TRIAD to improve control of these also. SPRUCE is 2,4DB, a clover safe hormone type herbicide.

Winter Barley

Rhyncho is present in most crops at various levels depending on the disease control already applied. The cool and damp weather pattern over the last month has been ideal for this disease, and without a robust and properly timed fungicide application this disease will move rapidly up the plant onto the upper leaves, awns and heads. Mildew is also present at varying levels. Ramularia is also beginning to show, with newer varieties showing greater sensitivity to this late developing disease. It tends to show late in the season usually after booting, symptoms are very similar to manganese deficiency.

The SDHI chemistry now available have a good position at T2 on winter barley crops where they retain green leaf and are very active against Ramularia. However whilst Bixafen (Bayer) and xemium (BASF) have curative activity, triazoles are still essential to the core of the T2 fungicide mix, with prothio, epoxi and flusilazole being the most robust for Rhyncho, both preventative & curative The SDHI actives are more long lasting than other chemistry groups, providing enhanced disease control and extending the protection period by up to 3 weeks. They also give consistent increases in green leaf area in the field, delay senescence and improve drought tolerance, all components that build yield.

Bixafen, available in mixture with prothioconazole as SILTRA for barley is particularly strong on Rhyncho. Xemium is also very strong but its partner triazole in ADEXAR, epoxiconazole is not as strong as the Bayer triazole. BASF also have boscalid, another SDHI active available in mixture with epoxiconazole as CHORD. Whilst the boscalid is not as curative as xemium, CHORD is very strong on Rhyncho and also has excellent activity on Ramularia at T2. Isopyrazam (Syngenta), in mixture with cyprodinil as BONTIMA for barley is particularly strong on rusts. None are particularly strong on Mildew or Fusarium.

Chlorothalonil is still an option when used preventatively to improve Ramularia activity but only when an SDHI is not being used at T2. (It has no activity on any other barley diseases.) FIELDER is an ideal triazole partner, combining both TALIUS and chlorothalonil in the one pack to control both  Ramularia and Mildew Where the SDHI chemistry is not being used, strobs also have a very important role in the T2 fungicide programme in those crops with good potential, improving control of Brown Rust, Net Blotch & Rhyncho. With a different mode of activity to the triazoles, it is an excellent partner in resistance management.

Winter Wheat

Most crops have now moved through the stages of stem elongation.Septoria tritici is present in all crops at variable levels depending on T1 timing. Mildew is also present in all varieties depending on whether TALIUS has already been applied.

The flag leaf will be emerging in most crops within the next week or two, and this is the key time to apply the T2 treatment. Of all fungicide treatments, T2 gives the greatest response in terms of grain yield and quality, keeping the top three leaves clean and the ear as it emerges. For this reason the manufacturers are targeting their new SDHI chemistry at this timing when the big spend will give the greatest return. Trial work on both sides of the Irish Sea last year showed consistently higher yields when these products were applied at this time.

While not as curative as the triazoles, each manufacturer claims extended persistency against Septoria for their SDHI actives. Co-formulated with triazoles, they all show excellent Septoria activity as well as extended activity on rusts and in the absence of disease enhance green leaf retention (similar to strob activity), so boosting grain-fill. Whilst their disease performance is not enhanced by the addition of a strob or chlorothalonil at this timing, from a disease resistance management point of view chlorothalonil should continue to be added.

Epoxiconazole and prothioconazole remain the key triazoles for controlling Septoria. However the difficulty in controlling this disease should not be underestimated. Part of any pathogen’s survival mechanism is to change in response to outside influences that adversely affect its development, and the Septoria pathogen is continuously modifying itself in response to a fungicides’ mode of action, developing ways around it. Population strains of the Septoria pathogen continue to change. New genetic variants are more able to tolerate particular fungicides, becoming harder to kill with epoxi and prothio (Group 1 triazoles). However these same strains are easily controlled with certain older triazoles including tebuconazole and metconazole (Group 2 triazoles). Hence the rationale for the best performing triazole products in recent years to be co-form triazole mixtures. In PROSARO, Bayer have demonstrated over the last 3 years that the effect of two triazoles mixed together is greater than the sum of both when used separately, the tebuconazole improving the product performance on Septoria over straight prothioconazole. BASF have identified a similar effect with BRUTUS, a mixture of epoxiconazole and metconazole. This product consistently outperforms straight OPUS, gram for gram and produces results in the field similar to PROSARO.

The rising temperatures over the last week have been very welcome for all crops but unfortunately awns have begun to appear on winter barley with critical plant growth regulator missed. Mildew is present on almost all winter cereal crops and should be treated at T2 timing. In spring barley & spring wheat an early application of ADJUST increases root development and the numbers of surviving tillers which will improve crop establishment and yield. Because of the spring crops more rapid progression through the growth stages than the winter crop, the growth regulator must be applied very early to maximise the suppression of apical dominance and therefore divert nutrients and growth to promote secondary tiller development. Optimum timing for barley is from the 2nd expanded leaf stage to beginning of tillering, GS12 – 21 whilst in wheat the optimum timing is slightly later, 5 leaf to mid tillering, GS15-24. This treatment also gives a consistent straw shortening effect in wheat, but not in barley.
Leatherjacket numbers are considerably higher this year with widespread damage to grass swards particularly in the west of the Province. Damage is now becoming evident in some of the earlier drilled cereals. Feeding activity and therefore the likelihood of damage will increase as soils continue to warm. Crops most at risk are those drilled into old ley or dirty stubble, but monitor all emerging crops closely for signs of damage. The grubs will be quite easy to find in areas of poor emergence, when the soil is dug down to a depth of 4-5cm.

Spring Barley

To minimise the effects of competition on the crop and optimise the level of weed-control, the herbicide application should be carried out sooner rather than later, once all the weeds have emerged but are still small, and before they begin to compete with the crop for nutrients and light. Product choice depends on the weed type and size present and crop growth stage. Broad leaved wise, Sulfonyl-urea (SU) herbicides will likely be the starting point, controlling a wide range of weeds and are very safe to the crop. 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 and fat-hen). Ideal partners are Compitox,Oxytril Cm and Spitfire. Each of these partner options are very tank mixable, and other products such as ADJUST and MAXMAN can also be safely added.
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 however, sulphonyl-ureas products will improve control. Spring barley, spring wheat and spring oats undersown with grass and clover should be treated with TRIAD and where clover is not important MIRCAM PLUS should be applied. If seedling docks, thistles and buttercup are also problem weeds, SPRUCE must be added to the TRIAD to improve control of these also. SPRUCE is 2,4DB, a clover safe hormone type herbicide.

Winter Barley

All winter barley crops have now received their T1 fungicide, with the T2 planned for the coming weeks. Prothioconazole in (MOBIUS or SILTRA) or epoxiconazole in (MANTRA or ADEXAR) at this critical timing will give maximum benefit over straight triazole products. Mildew levels are extremely high and thereforeTALIUS should be added.

Winter Wheat

Like the winter barley, the mild winter means Septoria and Mildew levels are higher than seen at the same time in recent years. Yellow Rust has also been found in some earlier sown crops and the threat will remain high. Robigus and Einstein have both broken down to new races of this disease and are more susceptible than ever. Like the barley, the T2 application should now be planned as recently applied fertiliser coupled with warmer temperatures will push crops through the growth stages very quickly.

Potatoes

With planting progressing well to date, this year’s crop is going in in almost perfect conditions right across the Province. Drills are moist and with this week’s increased temperatures rapid emergence of both crop and weeds will occur. Therefore growers should be planning weed control now, taking good advantage from the moist soil conditions. Most weed control programmes are based on residual products ie products that are taken up through the soil, and are therefore very dependent on sufficient soil moisture to work effectively. Soil conditions are ideal therefore at the moment, moist enough on the tops of the drills to allow the herbicide be taken into the soil and taken up by the germinating weeds. Contact products such as RETRO,ROUNDUP and TITUS may be applied. All require the inclusion of a residual partner to maintain clean drills up to the time of the crop canopy closing the drills. Residual products are DEFY, SENCOREX, AFALON and GAMIT.
All potato herbicides carry timing restrictions and some namely SENCOREX have varietal restrictions and it is therefore important to seek advice on the best product choice.
SHOGUN has a full recommendation for scutch control on ware potatoes. It will also give excellent control of perennial ryegrass, wild oats and volunteer cereals. If the crop is under drought or temperature stress when sprayed, transient yellowing may occur. For this reason its use is not approved on seed crops since these symptoms could be confused with viral disease.
Grass and weeds have been under stress up to now and where silage is still some weeks away there is an opportunity to apply herbicide.