This has certainly been a very changeable week with wintery showers and night frosts. Many crops are under stress and care should be taken not to rush out and spray these where timing is not crucial. Manganese deficiency is now commonplace in many crops, symptoms showing more in Continuous cereal ground and ground recently limed. Symptoms begin with small pale green speckles appearing throughout the leaf and these will progress to turn brown unless treated.
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 as soon as symptoms are seen.
SPITFIRE is now in its second season, it contains two active ingredients, a high loading of the sulfonyl-urea (SU) florasulam, and fluroxypyr. It has a very wide spectrum of weeds controlled including chickweed, cleavers, black bindweed, charlock, knotgrass, mayweeds and volunteer rape, and an equally wide window for application in all cereal crops. It can be used from 3-leaf of the crop GS13 right up to GS45 in winter wheat and winter barley; up to GS39 in spring wheat and barley; and up to GS31 in winter and spring oats, winter rye and triticale. Wild oats will continue to emerge in later drilled winter crops for another few weeks yet, so delay application until certain that all have emerged. To avoid crop damage, do not spray any crop under stress. Note that performance of some wild oat/brome herbicides can be adversely affected by other herbicides used on the crop. To avoid these antagonisms, a minimum time interval must elapse between application of the BLW herbicide application and this application.
Disease Control
The new fungicides containing an SDHI (Succinate Dehydrogenase Inhibitors) component add very cost effective yield benefits to both wheat and barley. Bixafen (Bayer), boscalid (BASF) and isopyrazam (Syngenta) are longer lasting than other chemistry groups, providing enhanced disease control and extending the duration of protection by up to 2 weeks compared to triazoles. This season sees the launch of another new SDHI molecule from BASF, xemium. In contrast to the other SDHI’s xemium appears to exhibit very good curative as well as preventative activity. Because this chemistry is considered to be at high risk to fungicide resistance, so they must only be used in mixtures with triazoles.
All of the SDHI’s give excellent activity on Rusts and Net Blotch. Bixafen, available in mixture with prothioconazole as AVIATOR for wheat and SILTRA for barley is particularly strong on Septoria and Rhyncho. Boscalid is available in mixture with epoxiconazole as CHORD and approved for both wheat and barley. As well as being very strong on Septoria and Rhyncho, it is the strongest molecule on Eyespot and therefore most suited to T1. It is also very strong on Ramularia in barley at T2. Isopyrazam, in mixture with cyprodinil as BONTIMA for barley and with epoxiconazole as SEGURIS for wheat is particularly strong on rusts. None are particularly strong on Mildew or Fusarium.
Xemium will be available in co-formulation with epoxiconazole, marketed as ADEXAR. As well as being one of the strongest performers against Septoria, because of its curative activity it is also the strongest product when timings have been stretched and therefore kickback is required.
Potatoes
Maincrop potatoes are currently being planted into ideal soil conditions right across the province. There are two types of herbicidal activity;
Contact herbicides which are those that must come into direct contact with the leaf of the target weed and will control all weeds that are emerged at the time of application – known as post emergent activity (post-em) and residual herbicides which move into the soil and prevent germination of the target weed before it emerges – known as pre-em
have only the one mode of activity; i.e. a contact will have no effect on weeds not yet emerged, while most residuals will not control weeds already emerged. In addition the residuals need sufficient soil moisture to work properly and in dry conditions residuals will not perform well.
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.
Grassland
Weed infestations can impact significantly on the yield and quality of grass for both grazing and cutting with trial work performed over the last two years by Dow Agroscience producing some shocking statistics. To put into perspective some of the figures, control of docks can give an average yield increase of 2.66t of DM/HA, enough grass for a cow to produce 5470 litres of milk. At 28p a litre this converts to £1531.00.Farmers will almost always apply fertilizer to grass swards because they can see the benefits but if I was to tell you that 3 bags of CAN could produce 320kg grass DM/HA which could produce 706 litres of milk at a value of £197.00 compared to dock control producing over 2000kg grass DM/HA which could produce 4452 litres of milk at a value of £1246.00.Which gives the better return?
It is important to allow one days growth for each 2-3 units of nitrogen between application and cutting to achieve good quality feed. Failure to use up the fertiliser applied may result in poor fermentation due to high levels of non-protein nitrogen in the crop. Docks are the most damaging weed which infests Northern Ireland farms. Part of the reason for the success of docks is that they will germinate and grow in almost any situation, and can then multiply by seed production or from underground roots. Seeds can be spread by a variety of means such as wind, water, stock and machinery. In most grassland fields there are approximately 12.5 million dock seeds per hectare in the top 15cm of soil and these can remain viable for up to 80 years. This seed bank provides an enormous reserve for reinfestation and reinforces the message that weed control is an ongoing battle not a one-off measure. It is important to remember that grassland herbicides are only effective when grass and weeds are growing actively and should not be used when there is a risk of low night temperatures.
The ideal time to spray docks is when they are in full leaf at the rosette stage just before the flowering stalk appears. For effective root kill it is necessary to use translocated herbicides such as dicamba, fluroxypyr and triclopyr to allow sufficient time for them to move from the leaves down into the root system. This is usually 3-4 weeks. Examples of products, which contain dicamba, are Grassland herbicide, Foundation ,Mircam Plus and Dockmaster. Doxstar and Pastor contain both Fluroxypyr and triclopyr and are preferred on silage ground as they have little or no effect on the growth of grass.Triclopyr has a much wider weed spectrum and greater translocation than straight fluroxypyr and therefore there is greater efficacy and longevity achieved by mixing these two actives especially on docks. 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.
Spot control of Nettles, Thistles and Docks can be achieved using Grazon 90 or Nushot.