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CROP CRACK 17-05-08
By WENDY FEARON
Clarendon Agricare - Sowing is Now Complete
The recent dry spell has allowed all of the spring cereal sowing to be complete with the earliest sown at mid tillering.Winter barley crops are now between GS (49-59) and the T2 fungicide should be applied at this time. Winter wheat crops vary from GS (38) with the most advanced crops now at GS (45) boots swollen.
Consideration must now be given to growth regulator.Cerone is the most effective straw stiffener during late stem extension. Based on ethiphon, this active can be quite severe on cereal crops especially in conditions we are experiencing at present. To overcome this, Cerone can be tank-mixed with Adjust at a reduced rate.
The T2 fungicide treatment on wheat should be carried out over the next week.T2 has the greatest impact response in terms of grain yield and quality, keeping the top three leaves and the ear clean as it emerges. Even with disease levels under control at the moment, the triazole dose applied at T2 must be sufficient to maximise the duration of persistency against re-infection in all weather situations right up to the T3 application time, some 4-5 weeks later. Sumi-alpha should also be applied as aphids have now taken flight from their over wintering sites.
SPRING BARLEY
Leather jacket damage has not been widespread in spring cereals due to the dry ground conditions. The warm conditions over recent weeks have encouraged the flight of aphids onto spring cereals. There is a serious risk of BYDV. Many newly emerged crops are now showing nutrient stress due to dry ground conditions.
Potash deficiency manifests itself as a very definite bleaching of the tips of the foliage in barley and wheat. Low ph soils are most at risk due to availability, heavy clay soils can also result in potassium being locked up and drought can affect K mobility within the soil and hence root uptake by the plant in soil water. Where soils are very high in magnesium, plants will be less able to take up potash. Potash is available in compound fertilisers, potassium nitrate, potassium sulphate and muriate of Potash. Poultry manure is the main organic source of potash.
Manganese deficiency is now also appearing on more forward spring barley crops.Deficency is common in crops ploughed out of permanent pasture, particulary if it has been overlimed, due to high organic matter levels. Poor root structure due to recent dry ground conditions will have affected the plants ability to take in manganese from the soil. Crops which have been rolled and the seed bed has been well consolidated are under less stress than those which are “puffy”.Maxman manganese is a soluble inorganic micronutrient containing 400gm/lt manganese and is applied as a foliar spray to help reduce deficiency. Because of the more rapid progression through the growth stages than the winter crop, ADJUST must be applied earlier to maximise the suppression of the main stem development and therefore divert nutrients and growth to promote secondary tiller development. Optimum timing for barley is from the 2 expanded leaf stage to beginning of tillering, GS12 – 21; in wheat the optimum timing is slightly later, 5 leaf to mid tillering, GS15-24.
This treatment will give a consistent straw shortening effect in wheat, but not in barley. In both crops it has a very significant impact on increasing tiller numbers and increased root development, consistently improving crop establishment and yield.
To minimise the effects of competition on the crop and optimise the level of weed-control, herbicide application should be carried out at the earliest opportunity, once all the weeds have emerged but are still small, and before they begin to compete with the crop for nutrients and light. Weeds have been slow to come through the ground but it is certain with the first drop of moisture coupled with warm temperature they will appear very quickly. Broad leaved Sulfonyl-urea (SU) herbicides are the first choice, but should always be tank-mixed with another BLW herbicide to control SU resistant weeds (chickweed) and those weeds not controlled by the SU’s (cleavers, fumitory, fat-hen).
Ideal partners: COMPITOX - chickweed, fat-hen, fumitory
OXYTRIL CM - field-pansy, red dead-nettle, speedwells
STARANE XL - chickweed, cleavers
Each of these partner options are very tank mixable, eg IPU, ADJUST can also be added.
Last year Dupont introduced a new version of ALLY called ALLY MAX SX. As well as containing a full rate (6gm/ha) of ALLY SX, the MAX version applies a further 6gm/ha of a second active, tribenuron. MAX therefore applies twice the grams of active as the old ALLY SX. The new ALLY MAX SX gives improved control of polygonums, fumitory and orache as well as a very wide spectrum of other weeds.
Where a wide range of BLW’s have become well established, HARMONY M SX is the best SU at controlling these larger weeds, and should be used in preference to other SU’s. HARMONY M SX in mix with STARANE XL is the best option for volunteer potatoes.
Where a typical mix of weeds are present (chickweed, redshank, fat hen, fumitory, day nettle) the hormone mixture products will work well without the need to tank-mix, but must be applied by GS31. Where some of the winter cereal weeds are also present however, (field pansy, forget-me-not, speedwells & corn-marigold) sulphonyl-ureas products will improve control.
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.
POTATOES
With planting almost complete consideration should now be given to weed control. Products containing Linuron should be used pre emergence of the crop and have residual activity. Performance of the residual herbicides is very dependant on soil moisture, and current dry conditions may hinder 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.
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