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CROP CRACK 31-05-08
By WENDY FEARON
Clarendon Agricare -Rain Has Arrived
Hopefully by the time you read this crop crack, most parts of Northern Ireland will have had some long awaited rain. It has been almost two months since some parts of Co Down has had any rain and grass, vegetable and cereal crops are under severe stress. Ground conditions have been so dry; fertiliser applied at sowing is still visible. Nutrients are not being released into crops especially manganese. It is essential to apply either Maxman manganese or Cereal Plus to crops showing signs of deficiency. As predicted in previous crop cracks BYDV symptoms are now appearing in early drilled crops. I am recommending an application of chlormequat (ADJUST) onto all spring cereal crops at this time as the growth is soft and floppy and the root structure is very poor.
CEREALS
Weeds are now ideal for spraying but crops will quickly reach first node and a hormone such as Mircam Plus may be applied up to this time.Mircam will control a wide range of BLW’s including (chickweed, redshank, fat hen, fumitory, day nettle and thistle) .ALLY MAX may be applied from the three leaved stage of the crop up until the flag leaf is fully emerged.COMPITOX must be added to all SU’s to give adequate chickweed control (NB check latest timing for CMPP).STARANE XL may be tank mixed along with Ally Max up until the flag leaf is fully emerged,STARANE XL will also give excellent control of volunteer potatoes.FIELDGARD (IPU) has a Specific Off-Label Approval (SOLA No 2320/2004) for control of AMG up to early tillering GS22 in spring barley and spring wheat (not spring oats). A better option is HUSSAR – it controls larger AMG at this time of year, up to the end of tillering GS30 and also controls a range of BLW very similar to the other SU’s. However as an SU, it will not control chickweed, fumitory & fat-hen, so must be tank-mixed similarly.
Where cereals are undersown herbicide choice will depend on whether clover is included in the grass seed mixture. Where clover is not present, MIRCAM PLUS is the best option. If clover is part of the mixture, ALISTELL will give good control of small chickweed but is poor on seedling docks.REDLEGOR or TROPOTOX PLUS may also be applied to undersown cereals but neither will control chickweed
The performance of wild oat herbicides is adversely affected by other herbicides used on the crop. To avoid these antagonisms and possible damage to the crop, a minimum time interval must elapse between application of the BLW herbicide application and the wild oat herbicide application. The best option is to get the BLW treatment on as soon as possible to allow the maximum interval elapse for the wild oat treatment. GRASP gives excellent control of wild and tame oats in spring barley. Application should be held off until at least 6 weeks after drilling to ensure all wild oats have germinated. It can be applied up to full flag-leaf of the crop, but will only control the wild oat up to 1st node GS31. Where the oat gets beyond the 1st node stage, AXIAL is an alternative, controlling the oat up to full flag leaf GS39. Both products require the addition of a wetter.
GRASP or AXIAL can also be used in spring wheat, but CHEETAH SUPER has a similar crop spray window and a wider wild oat window and does not require a wetter.
Disease levels remain relatively low but fungicide programs should have begun on more forward crops. Mildew and rust are appearing onto more susceptible varieties of spring wheat with net blotch being the most dominant disease on spring barley at present. More cases of ramularia are now being reported in Northern Ireland than there have been in the past.
Strong sunlight, prolonged leaf wetness, agrochemical scorch and nutritional stress can all trigger physiological leaf spots, associated with the fungus Ramularia in barley, but because the disease develops so late in winter barley it usually causes very little economic loss. Chlorothalonil is a very important part of both spring barley and winter barley fungicide programmes to achieve ramularia control.
POTATOES
Potato planting is now complete and a fair bit of weed control is yet to be carried out due to dry conditions.
Performance of the residual herbicides is very dependant on soil moisture, and current dry conditions have hindered the performance of the product. Any ridging up should be done before application of a residual, as any soil disturbance after application will adversely affect performance. Emerged weeds will be controlled when application of the residual is delayed as late as its label allows, and a contact herbicide added. This also benefits the residual performance by allowing it to persist later into the season up to the point where the crop canopy will cover the drills and prevent further germination. Products containing Linuron should be used pre emergence of the crop and have residual activity. Retro which replaces PDQ can be applied on earlies and seed up to 10% emergence and main crop up to 40% emergence provided the plants are no bigger than15cm high. An additional wetter must be applied such as Activator 90.Sencorex which is both contact and residual may be applied on specified varieties pre emergence up to when stems are 15cms in height. Alternatively Sencorex and Titus may be used up until the main stem is 25cm and an adjuvant such as Libsorb must be added. Where scutch is a problem in ware Falcon may be used.
Two new contact herbicides have also come to the market this season. Based on glufosinate ammonium, Bayer have launched BASTA for spring weed control in seed and ware. BASTA is the most robust option, controlling a full spectrum of BLW and grass weeds at a relatively large size. However it must be used pre emergent of the crop and before any ridge cracking has occurred, as it will destroy the mother tuber of any emerged sprouts. It must therefore be used early in mix with a strong residual.
Belchim market a contact product containing carfentrazone, SHARK. It has activity on some BLW but no activity on grasses. It is weak on chickweed, charlock, fumitory and groundsel. Its activity on all other BLWs drops off rapidly beyond the 4-leaf stage. Like RETRO therefore, it will have to be applied early and mixed with a good residual.
Where scutch is a problem in ware Falcon may be used.
Fungicide treatments have begun on early potatoes although blight pressure up until now has been at an all time low.
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