Getting the spray application right when applying pre-emergence herbicides is crucial. For some tips to optimise control from residual herbicides this autumn click here….
Spring crops are looking very well and without the more usual effects of waterlogging seen in other years. Although weeds are emerging fast as a result of last week’s rain, be sure all are well through before spraying. Also watch the size of the annual meadow grass if this weed is also to be controlled – efficacy falls off rapidly once it begins to tiller. It is important to note that this season aphid numbers are the highest I have seen for a very long time and it would be advisable to apply an aphicide to control the spread of BYDV.
To minimise the effects of competition on the crop and optimise the level of weed control, herbicide application should be carried out once all weeds have emerged but are still small, and before they begin to compete with the crop for nutrients and light. Carrying out the weed control when they are at the 2-4 leaf stage is much more effective especially on difficult weeds such as fumitory and knotgrass, rather than delaying to coincide with the 1st fungicide application.
Broad leaved weeds resistant to particular groups of herbicides in NI is not a new problem – chickweed resistant to herbicides such as ALLY has been widespread throughout the province for some years. Sulfonylurea (SU) herbicides such as metsulfuron have a single mode of activity, blocking the production in many BLW of a key enzyme, acetolactate synthase. Products that use this mode of activity are known as ALS inhibiting herbicides and include the SU chemistry. As well as chickweed, mayweed and poppy have also developed widespread ALS resistance. This particular resistance problem has been managed by including herbicides into the tank-mix with different modes of activity to maintain good weed control.
In spring cereals, ZYPAR will give excellent control of a wide range of weeds that will not be controlled by Ally on its own. These include chickweed, fumitory, fat-hen, groundsel, brassica weeds, and cleavers. It’s one relative weakness is redshank. Whilst it will control it to 6-leaf, it should be tank-mixed with another herbicide to ensure redshank right up to flowering is satisfactorily controlled. ALLY MAX and SAXON are excellent tank-mix partners for this purpose.
Winter cereals have greened up well and are now racing through the growth stages. Awns are now out on almost all winter barley crops with growth regulator applications complete. The cool nights during April held back the crop response to nitrogen, but this has turned around and all nitrogen applications should be completed in the coming days to maximise green leaf development and crop yield.
Winter wheat crops which have not yet received T2 should be treated as soon as possible along with the growth regulator if required. The cool dry April and well timed T1 treatments have kept Septoria infection low, but it is present in all crops and remains a key focus for T2 treatments planning forward. Yellow Rust has been observed at low levels but perhaps a combination of cold nights and effective varietal resistance has meant that there have been no explosions of infection we were more familiar with other years.Zypar Strapline
A good start has been made to drilling spring crops, with the earliest drilled now emerging in the more forward areas. After a very mild winter, the colder temperatures during the first half of April slowed development in all winter crops, with many fields actually going backwards. The cold night-time temperatures have been very stressful to winter crops, hampering nutrient uptake causing purpling, yellowing and tipping of some leaves. However warmer temperatures and rain over the last week has improved everything, with all winter crops now looking much better. What is clear given current pricing it is more important than ever to optimise fertiliser applications to maximise the efficiency of utilisation of N, P and K. Soil pH is key – make sure this is above 6.2 for winter and spring crops. Granulated lime at around £125-135/t is excellent value and we should see a lot more of the granulated lime being applied to improve NPK utilisation. Correct use of foliar feeds also has an important role to play, where often it is not the amount of N applied that is the limiting factor, but perhaps sulphur or one of a number of micro-nutrients.
The size of canopy at GS30-31 is a good indicator of future lodging risk, with larger canopies associated with greater lodging risk. Assess lodging risk on a field-by-field basis, also taking account of the field soil residual N and lodging history, and the varietal lodging resistance score. Numerous other factors contribute to crop lodging including sowing date, early growth over the winter months, and late season extreme weather events.
Against this background, a programmed approach made up of a number of treatments promoting shorter and stronger stems is essential. Plant growth regulator (PGR) choice, timings and rates all impact the outcome achieved. Early sown crops with thick canopies are most at risk of lodging, particularly if of a weaker strawed variety, and will require a more intensive programme to minimise the risk of lodging
With a better understanding of disease resistance to single-site triazole, SDHI and strobilurin chemistry, maintaining the efficacy of this chemistry is critical to being able to continue to control wheat and barley diseases effectively. Multi-site chemistry is key to prolonging the efficacy of the single-site chemistry. Chlorothalonil (CTL) was the mainstay of multi-site activity for years, but with its loss two seasons ago now, folpet, available from Syngenta as MIRROR is regarded as the most effective replacement.
Folpet is a multi-site active, and all manufacturers are advocating the inclusion of this active into wheat and barley programmes, not only to prolonging the single-site actives, but to improve disease control also. Its inclusion improves Septoria activity in wheat and gives some improvement of Ramularia in barley. Like CTL, folpet is a contact ingredient only with no systemic activity, protecting the surface of the leaf by preventing the fungal spores germinating on the surface of the leaf.
Early weed control – Annual Meadow Grass In Spring Crops
If Annual Meadow Grass (AMG) is to be controlled in spring crops, this must be done as soon as possible. This will be done before the timing for controlling broad-leaved weeds (BLW) in spring cereals. There are a number of product options, but all must be applied either pre-emergent or in the case of one, very early post-emergent of the crop.
Applied pre-emergent, all work by residual activity to control the AMG. Since residual herbicides require sufficient soil moisture to be effective, so their performance will be compromised in drier soils. This is the primary reason for the variable performance of AMG control achieved in the spring. Best control is achieved when applied onto a damp seedbed, keeping the water volume up and travelling slowly. To maximise efficacy and crop safety, ensure the label guidelines are strictly followed.