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Crop Crack 23.04.11
By Wendy Fearon
World grain stocks are at an all time low and with oil very firmly on the up this increases the demand for energy uses for cereals. Spring is certainly here and dry soils coupled with rising air temperatures are beginning to show some noticeable signs of growing on all crops. Colour is improving daily as the nitrogen becomes more mobile within the plant. Those crops which have a low k index are noticeably behind those which are higher.
Any herbicide applications should be completed as soon as possible onto all winter crops. Manganese deficiency is now commonplace in many crops, symptoms showing as growth gathers pace. Continuous cereal ground and ground recently limed is most prone to deficiency. 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 a new herbicide from Dow containing 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
In our climate maximising yield means controlling disease effectively. Getting timings right is absolutely essential; ‘fire-brigade’ control of disease is more costly and a lot less effective than well timed preventative control. Except in very low disease pressure conditions, it is a false economy to skimp on disease control and get away with it - all independent work shows that increasing fungicide doses does also increase yield.
This season sees the launch of a number of newly approved cereal fungicides containing a new family of chemistry known as carboxamides. Bixafen (Bayer), boscalid (BASF) and isopyrazam (Syngenta) are more long lasting than other chemistry groups, providing enhanced disease control and extending the duration of protection by up to 3 weeks. Whilst they have some curative activity, their strength is protectant and therefore are available only in mixtures with triazoles. They also give consistent increases in green leaf area in the field, delay senescence and improve drought tolerance, all components that build yield.
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 appears 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 also has excellent activity on Eyespot at T1 and 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.
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-emergent activity (pre-em).
Most herbicides 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.Retro, Roundup Energy and Titus are all contact herbicides whereas Sencorex, Defy and Linuron are residual.
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
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. Use plenty of water, about 30-40 gallons per acre, and do not spray in strong sunlight. 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 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.
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