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Crop Crack 09.05.09
By Wendy Fearon
It is hard to believe but there is still a percentage of spring cereals yet to be sown. Any crops sown early have emerged well, and whilst aphid numbers are not very high it is advisable to apply an aphicide such as SUMI-ALPHA along with ADJUST soon after emergence.
Warmer soils and damp ground will increase feeding activity of leather-jackets. Crops most at risk are those drilled into ley or dirty stubble, but monitor all emerging crops closely for signs of damage such as whole plants yellowing or cut off just below ground level. The grubs will be quite easy to find in areas of poor emergence, when the soil is dug down to a depth of 4-5cm.
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, and 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. With good seed-beds and increasing soil temperatures, weeds will come through rapidly. Broad leaved, Sulfonylurea (SU) herbicides are the first choice, but should always be tank-mixed with another BLW herbicide to control SU resistant weeds such as (chickweed) and those weeds not controlled by the SU’s (cleavers, fumitory, fat-hen).Ideal partners are COMPITOX,STARANEXL or OXYTRIL CM .
Wild Oats
It is important to note that 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.
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 the 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 (different) wetter in all situations.
GRASP or AXIAL can be used in spring wheat, but CHEETAH SUPER has a similar crop spray window and a wider wild oat window, and is more cost effective.
Growth Regulation
Winter barley is flying through the growth stages at present with many crops now at full flag leaf, GS39 and a few have awns fully out.
In many cases the T1 fungicide has likely only been applied in the last 10-14 days, somewhere around 1st–2nd node of the crop. This timing is too soon to get consistent strengthening of the winter barley stem. Yet to wait another 2 weeks and apply a growth regulator when the T2 fungicide is due to be applied will be too late. To delay application of the growth regulator will be a case of bolting the stable door after the horse has bolted and may cause damage to the emerging ear – it is essential this job is done now before the awns start to appear to get maximum response, and minimize any danger of damaging the crop!
In winter wheat the weakest part of the stem tends to be the lowest internodes, whilst in barley it is the higher internodes. In winter barley the T1 PGR (plant growth regulator) application enhances root anchorage, but has less of an effect on controlling stem lodging at this time than in wheat. It is during the later stem extension stages and early flag leaf emergence that the maximum straw strengthening effect will be achieved. The efficacy of the application beyond this timing drops off rapidly, as with each passing day the stem has already added on further length.
Product choice depends on timing, if applied during early stem extension (2nd-3rd node) then MODDUS is the most effective. If applied from the beginning of flag leaf emergence then CERONE is more effective. ADJUST should be added to either product - the mixture is cheaper, considerably safer than and equally as effective as the straight product.
Cereal Disease
All cereal crops benefit from a well timed fungicide application. Spring barley should be treated at mid tillering with MIDAS, COLSTAR or MANTRA to protect against rhynchosporium and TALIUS should also be added to Colstar or Midas for mildew control.
The T2 second fungicide application onto wheat should be done at flag leaf as this part of the plant contributes to most of the yield. It looks like the T2 timing onto winter barley may be late as a lot of the winter barley has only received the T1 over the last few weeks. There is no doubt with the amount of rainfall we have had crops will definitely be under threat from ramularia this season and this should be considered when deciding the fungicide treatment.
Winter Oilseed Rape
The showery conditions over the last week will increase the risk of petals sticking to the crop causing sclerotinia. Something like PROLINE should be applied at this time.
Potato Weed Control
Weeds are emerging in potato crops at an exasperating rate. Growers need to be very quickly assessing which weed control option they will choose. RETRO and Activator may be applied to all varieties and may be applied up to 10% emergence on earlies and 40% on maincrop.LINURON may also be mixed with RETRO up to 20%emergence where variety and soil type will not allow the use of SENCOREX.SENCOREX must not be used on very light sandy soils and must only be applied to named varieties.
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