This has certainly been a very changeable week with wintry showers, high winds but most importantly increased temperatures. 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 Manganese deficiency – it’s 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.
Othello and Bio Power are now the best option for weed control in winter wheat only. These actives are contact only and therefore need the grass to be completely emerged and growing actively, and are very effective on larger annual meadow grass. In addition they also have activity on a range of broad-leaved weeds.
Spitfire is now in its third season and has given excellent weed control over the last couple of years. It contains two active ingredients, a high loading of the sulfonyl-urea (SU) florasulam, and fluroxypyr. It controls a very wide spectrum of weeds 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 any antagonism, a minimum time interval must elapse between application of the BLW herbicide application and this application. The time has now passed to treat grass weeds in winter barley. Once spring growth commences properly contact herbicides give more reliable control, but their efficacy is critically linked to improving soil temperatures and active weed growth having begun.
Growth Regulation and Managing Thin Crops
When applied early enough in the plant development, application of certain chlormequat growth regulators can significantly increase tiller numbers. Both ADJUST and SELON work by suppressing apical dominance, ie main stem development. In doing so it diverts the plant’s resources into producing and supporting more tillers. Particularly in wheat but in barley also, more tillers will go a long way towards compensating for low plant counts, ultimately increasing yield. The biggest yield responses to this early application are seen in thin crops, as most crops are this season.
Timing is critical to maximise this effect. Application of a chlormequat based growth regulator often goes on with a T1 fungicide application sometime around 1st-2nd node, GS31-32. At this timing however it is too late to affect tiller numbers and survival, primarily only serving to stiffen the stem at this time. The earlier it is applied during tiller development the greater the tillering effect.
Early application will also increase root growth and so reduce stem-base lodging. Stem-base lodging is where the plant folds over at the soil surface as a result of poor anchorage in the soil, and is caused by poor root ball development, more likely when the seedling develops in wet soils that limit root development. All winter crops have rooted very shallow this season as a result of the persistently wet conditions and therefore stem-base lodging is likely to be a significant problem later this season.
Maincrop potatoes are currently being planted in pockets across the province. Drills are moist and with a bit of heat hopefully to come, will encourage rapid emergence of crop and weeds. Therefore growers should be planning weed control now, taking good advantage from the moist soil conditions.
Most weed control programs are based on residual products i.e. products that are taken up through the soil, and are therefore very dependent on sufficient soil moisture to work effectively. Soil conditions are ideal therefore at the moment, moist enough on the tops of the drills to allow the herbicide be taken into the soil and taken up by the germinating weeds.
With stocks of silage very low and a late start to the season there is a need to maximize grass yields for grazing and silage this year. With very high feed prices it has never been more important to get the most from your grass. Grazed grass is the cheapest feed on your farm. However yields can be very severely impacted by weed infestation. With conacre prices higher this year, farmers need to maximize the potential on their own land before deciding to rent what could be expensive ground. Weed control can run from as little as £6.00 up to £20 per acre depending on target weeds. This expenditure will not rent a lot of land but can make a huge impact on grass yields on your farm.
As much of the of the grassland acreage went untreated for weeds last year it is important to inspect fields intended for cutting and grazing in order to allow the spray interval for stock rotation. Grass growth to date has been very poor but hopefully with the heat this week, growth will improve.
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 re-infestation 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. Over the last 5 years Forefront has been the outstanding product for controlling docks in Northern Ireland. In addition to docks it will also control nettles, thistles, buttercups, ragwort and chickweed giving a complete clean-up in your fields.
With many fields showing the effects of the last couple of wet years, rushes have become a major issue on farms in Northern Ireland. Rushes are relatively easy and inexpensive to control. Spray rushes when they are green and actively growing, and always add a wetter/sticker(e.g. Activator) to enhance uptake into the plant. Due to the shape of the rush, there is always potential for spray run-off, which the wetter will help to prevent. The most popular products for controlling rushes in Northern Ireland include Agritox and Spear.