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All winter barley crops all looking well and the gates are now closed until desiccation takes place in the coming weeks. Most winter wheat crops have received their T3 earwash with a few later drilled crops still to be sprayed. Tebuconazole is the most effective triazole for Fusarium in particular and an important active in its own right at this time. The addition of a strobilurin is essential to maximise the persistence of the triazole, to strengthen activity on Yellow Rust, and delay early leaf senescence. 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.
Aphids in cereals
As the grains begin to fill the aphids begin to feed at its base on the ear, drawing off the sugars that should be filling the grain if left unchecked. Growers need to continue checking crops for aphids right up to early milky ripe stage (GS73) in barley, late milky ripe (GS77) in wheat, and spray if present in numbers. Where aphids are not present, unnecessary application should be avoided as any insecticide application at this time is not bee friendly. Of the aphicides approved for use for this purpose, SUMI-ALPHA is the least harmful to bees.
Pre Harvest Glyphosate
Winter barley crops are ripening well and thoughts will now turn to grain quality, moisture levels, and ease of harvesting. Pre harvest application of glyphosate is an essential tool to improve the efficiency of harvesting, giving a range of benefits. It looks like propionic acid is going to be unavailable this year so there is even more need for pre harvest glyphosate.
Independent trials carried out over a number of years in GB, looking at the effect of using Roundup in various replicated treatments consistently show moisture contents being reduced by 2.0-2.5% at harvest compared to plots where no treatment is applied.
Application should be made once the grain moisture gets down to 30% or below, ideally 10-14 days (and not less than 7 days) before cutting. An easy and reliable test to estimate this 30% moisture level is to press the thumbnail into a number of grains; if the indentation holds on all the grains the crop is ready for spraying.
Most spring cereal crops continue to benefit from the recent hot weather with many racing through the growth stages in a matter of days after the early spring conditions. With temperatures now well above average and daylight hours considerably longer than for a crop drilled in early April, such conditions increase the likelihood of crop stress through too little moisture, or not enough nutrient availability to support the potential rate of growth. As a result many fields are beginning to show variation of colour and growth, and such variation is very difficult to address in a satisfactory way. Manganese (Mn) deficiency is widespread in much of our local soil types, and particularly damaging if not treated. Continuous cereal cropping, ground recently limed and dry soils all increase the likelihood of deficiency. Symptoms begin with small pale green speckles appearing throughout the leaf and these will progress to turn brown unless treated. Barley is particularly susceptible to Mn deficiency.
A young plant that is growing extremely rapidly is producing a huge amount of new plant tissue each day. This rapid growth is limited only by the availability of nutrients to synthesise biomass, dependant on soil fertility and the plant’s own root development to take up the nutrients. It is at this time therefore when nutrient deficiencies are most likely to appear and in doing so, suppress growth rates.
The application of a broad-spectrum trace-element mix along with key macronutrients during this time is a very useful and beneficial way to supplement the plant’s nutrient requirements during periods when availability does not meet demand, most likely to coincide with phases of rapid growth. Application of a balanced and readily available source of macro & micronutrients that is topping up what is being made available from the soil at this key time will minimise the adverse effects of restricting nutrient availability.
CEREAL HIGH N supplies 250gm N,38gmMg,45gm Cu and 15gn Zn per hectare
Disease pressure has been lower than that seen for a long time on winter cereals and fungicides are now complete on winter barley. T2 applications should now be complete on winter wheat crops.
Dry conditions have held back disease and at present all crops are fairly clean, but in our typically moist climate the likelihood of Rhyncho and Net blotch infections breaking out are inevitable unless controlled in good time.
Even where crops are considered to be clean, controlling Rhyncho early is much more effective than leaving it until it is seen. Once this disease comes into the crop, any eradicant treatment has limited efficacy, will stress the crop and increase the risk of Ramularia infection.
The young spring wheat plant isn’t subjected to the same disease burden as the overwintered winter wheat plant, therefore a two-spray programme usually suffices, with the T1 applied at 1st-2nd node, GS31-32, and the T2 applied at some point during booting, GS41-49. Whilst a large proportion of these crops are harvested as whole-crop earlier than the conventional combined crop, the feed quality of the harvested crop is very dependant on maximising grain-fill, therefore product choices and rates are similar to those of the winter crop, with significant yield responses to a proper programme.
Application of SELON at early tillering will have increased tiller and ear numbers and therefore yield potential, but will not have given any reliable strengthening of the straw. Stems that extend rapidly during the stem elongation phase (as has happened this season because of late planting and high temperatures) are more likely to be weaker and so there is a greater risk of lodging especially where the crop is being pushed on with nitrogen. SONIS can be used but its cut-off in spring barley is 2nd node, GS32. CANOPY is a very useful alternative, safe to the crop and able to be used right up to and including full flag leaf, GS39.
Because the application of SELON at mid to end of tillering (GS23-30) does give reliable later season lodging control in wheat, it is less likely than spring barley that spring wheat will need a growth regulator towards flag leaf unless the crop is particularly dense.
The more pleasant night-time temperatures have seen a welcome burst of new growth in all crops. All spring crops are looking very well and without the more usual effects of waterlogging seen in other years. Although weeds are emerging fast as a result of last week’s rain, be sure all are well through before spraying. Also watch the size of the annual meadow grass if this weed is also to be controlled – efficacy falls off rapidly once it begins to tiller. It is important to note that this season aphid numbers are the highest I have seen for a very long time and it would be advisable to apply an aphicide to control the spread of BYDV.
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 when they are 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 1st fungicide application.
Broad leaved weeds resistant to particular groups of herbicides in NI is not a new problem – chickweed resistant to herbicides such as ALLY has been widespread throughout the province for some years. Sulfonylurea (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. As well as chickweed, mayweed and poppy have also developed widespread ALS resistance. This particular resistance problem has been managed by including herbicides into the tank-mix with different modes of activity to maintain good weed control.
In spring cereals, ZYPAR, which contains Arylex, will give excellent control of a wide range of weeds that will not be controlled by Ally on its own. These include chickweed, fumitory, fat-hen, groundsel, brassica weeds, and cleavers. It’s one relative weakness is redshank. Whilst it will control it to 6-leaf, it should be tank-mixed with another herbicide to ensure redshank right up to flowering is satisfactorily controlled. ALLY MAX and FOUNDATION are excellent tank-mix partners for this purpose.
Winter cereals have greened up well and are now racing through the growth stages. Awns are now out on all winter barley crops with both T2 application and growth regulator applications complete. Winter wheat crops which have not yet received T2 should be treated as soon as possible along with the growth regulator if required.