The more pleasant night-time temperatures have seen a welcome burst of new growth in all crops. All 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, which contains Arylex, 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 FOUNDATION 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 all winter barley crops with both T2 application and growth regulator applications complete. Winter wheat crops which have not yet received T2 should be treated as soon as possible along with the growth regulator if required.