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Crop Crack 21.04.10
By Wendy Fearon
Temperatures are fairly average for the time of year but soils are beginning to warm and with nitrogen applied over the last few weeks, so crops are now starting to grow. Night time temperatures still remain low so care must be taken when applying herbicides containing hormone such as CMPP onto crop. Trace element deficiencies are showing up widely, mostly Manganese but also Zinc in some cases.
Potato and vegetable planting have begun and most of the grassland acreage has received fertiliser over the past few weeks. Early sown spring cereal crops should be inspected now for leatherjackets. Where numbers are found to be above the threshold limits, the best control is achieved by applying Dursban WG or Cyren. Highest risk situations are fields coming out of long term ley or stubble fields with good grass cover.
Winter barley
It is now too late to control annual meadow grass in winter barley and crops which have not yet received a herbicide, only the broad leaved weeds can be controlled. ALLY MAX in a tank mix with a suitable partner should be applied in this case.
Levels of disease are extremely varied at present with crop variety and sowing date playing a big part in this. It is essential to get the T1 application on when the crop has reached first node stage, GS31. Due to the very damaging effects of rhyncho, delaying beyond this timing will adversely impact on yield and will not be undone by later applications. The addition of chlorothalonil will add to the rhyncho activity, and provide protection of Ramularia later.
Use flusilazole or epoxiconazole as the base at T1 for good curative and persistency at low cost. Products such as PUNCH C, MIDAS or MANTRA are good choices at this time.
Winter wheat
The best option now for well tillered annual meadow grass in winter wheat is the Bayer sulfonyl-urea (SU) actives iodosulfuron & mesosulfuron contained in OTHELLO.Bio Power must be added to Othello at all times. These actives are contact only and therefore need the grass to be completely emerged and growing actively. In addition they also have activity on a range of BLWs.Othello may not be applied beyond first node. The other option is HUSSAR in a tank mix with either hormone or STARANE XL.Hussar requires warm conditions and soil moisture to work effectively and may be used up until 3rd node.
The wheat T1 application should also be applied around the first node stage. The T1 treatment is targeted to control Eyespot, eradicate any Septoria tritici already present and prevent further re-infection for at least 4 weeks. Fluquinconazole in FOIL is a very cost-effective triazole, as is epoxiconazole in OPUS if more curative activity is required at T1.Chlorothalonil should be included in all T1 programmes without exception. TALIUS (proquinazid) is the strongest active on barley and wheat Mildew, lasting up to 2 weeks longer than existing standards. Powdery mildew is already present on some varieties.
Potatoes
Main crop potatoes are currently being planted into ideal soil conditions.
All residual herbicides need adequate soil moisture to work effectively. All herbicides should be applied early to be effective as none of the alternative contact products will control the same size or range of weeds as products used in the past. Any ridging up should be done before application of a residual herbicide, as any soil disturbance after application will adversely affect performance.
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. 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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