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Crops ahead but disease and growth challenges

Excellent weather conditions over the past few weeks means that most spring field work has been completed on time. Most winter oilseed rape crops are already at the early stages of flowering. But the frosts of last week have slowed development.

Many of these crops have received a fungicide or growth regulator with boron and magnesium. The last of the nitrogen should be on, bringing total levels to about 225kg/ha. Nitrogen applied close to flowering is recommended to ensure better grain fill and yield. The ability of your fertiliser spinner to spread nitrogen accurately will determine how late you can apply nitrogen to your rape.

There is also evidence of light leaf spot in some crops, especially in the south of the country. The application of Folicur or Caramba (if not already applied) with boron and magnesium is recommended.

I found my first pollen beetles in crops in the Carlow region last week. However, levels were below the threshold of 10-20 beetles per plant at flowering, so treatment is not warranted. It is recommended that no treatment be taken until about 90pc petal fall to avoid damage to beneficial insects such as bees.

Winter wheat crops are 1-2 weeks ahead of normal and significantly ahead of last year. While early morning frosts last week slowed development, the application of a plant-growth regulator is urgent in most cases, especially for the early sown wheats.

Most crops are at GS31 or even GS32. Septoria is widespread and mildew is evident in some varieties, especially in Cordiale and Lion. Some yellow rust is evident in Lion and Oakley in the south east.

The second split of nitrogen, which is often half the total added, should be applied now.

Consider splitting this for very advanced crops as this helps to reduce the risk of lodging and leeching. Sulphur should be applied with the nitrogen and, in high lime soils, the addition of potash is beneficial and helps improve straw strength.

With winter crops being so advanced this year, trace elements might be considered. Copper, zinc and manganese should be applied by mid-tillering and completed by the first node (GS31). For growth regulation, CCC products should be applied before GS31 to maximise the shortening effect.

Lodging can be further reduced if the CCC is split between GS31 and GS32, especially in high-risk situations. Meteor can be applied up to GS32 or a mixture of Modus at 0.2l plus 1l of CCC at GS30-31. For crops past the first node, the products applied will only shorten the top inter-nodes and are ideally suited for a follow-up treatment where risk of lodging is particularly high.

It is still early to be considering your T1 on winter wheat. A T0 of chlorothalonil plus morpholine and a strobilurin for mildew and yellow rust might be considered. The T1 fungicide application should be delayed until the third leaf has fully emerged (around GS32).

In relation to winter barley crops, most are at GS31, with advanced crops at GS32.

Rhyncosporium and mildew is present in most crops but is not moving due to the cold weather. Brown rust is at low levels in some six-row varieties, especially Leibniz. The second split of nitrogen should be applied now at GS31-32. Some cleavers and wild oats need control at this stage.

Some crops received a T0, while T1 applications of a fungicide should be considered in the next two weeks. This should consist of prothioconazole and a strobilurin at a half rate. Growth regulators, Cerone, Terpal or Modus plus CCC should be considered between GS32-37, as they can reduce the plant height by up to 15cm.

Winter oats were being considered for ploughing out this time last year. This year, however, the crops are extremely advanced up to or close to GS32 in many cases. Mildew is significant in many crops and the early addition of a morpholine appears to have worked well.

Some red-leather leaf disease is also evident. Fertiliser should be completed by GS32, bringing the level up to around 145kg for index 1 crops. Trace elements are vital, particularly manganese, on light and high pH soils.

A second plant growth regulator such as Ceraide could be considered at GS32-33. A maximum of 2.3l/ha should be used and a T1 fungicide, incorporating a mildewcide and a broad spectrum fungicide, should be included with the growth regulator. The inclusion of a preventative mildewcide such as Talius or Flexity will prolong protection from mildew.

Most spring cereals have now been drilled, with some spring barley to be sown in the northern part of the country. Early sown crops are emerging nicely and top dressing should now be considered. If soil samples allow, a compound fertiliser should be applied on emergence, with up to 50pc of the nitrogen requirement applied now.

Beans sown in the past month have emerged and most crops have been treated for weed control. Graminicides may be required at a later stage for the control of wild oats or scutch.

Sowing of spring oilseed rape has begun in the south and east. A fine and firm seed bed is essential, so rolling immediately after sowing is recommended. Aim to sow at 100 (hybrid) or 130 (conventional) seeds/m2, or around 4-6kg/ha, depending on thousand grain weight.

A total of 130-150kg N/ha will be required with P and K, depending on soil index. Index 3 needs 20kg of P and 30kg of K. With early sowing, weed control is vital. Use Butisan at 1-1.5l/ha immediately after sowing. Moist conditions are preferable. Later sown crops will not require any broadleaf weed control as early growth can smother weeds.

Pat Minnock is a Carlow-based member of the ITCA. Email: www.minnockagri.ie

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