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Thursday 8 December 2016

Carefully consider herbicide choice particularly if weeds often seem to escape the effects of chemicals

Pat Minnock

Published 03/05/2011 | 05:00

After an excellent spring and with winter crops two to three weeks ahead of normal, a slowdown in growth and development was noticeable last week mainly due to lack of moisture.

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Spring barley has been particularly affected by this lack of moisture. The early March-sown crops are in good condition and are able to withstand herbicide application. However, some of the later-sown crops are struggling. While I always like to apply an early and low dose of herbicide for early weed control, this year I have tended to withhold spraying due to the pressure they are under.

Any late March or early April-sown crops would benefit from liquid phosphate application together with some trace elements and an aphicide. If herbicide application is being delayed, slightly higher rates may be needed.

There are a wide range of sulfonylurea products available on the market for a range of weed problems. Most of these need to be tank mixed with either Duplosan, Starane, Galaxy or Oxytril, Stellox or Swipe. The choice of herbicide mix will be determined by the range of weeds present. If some weeds appear to be escaping every year, a change of herbicide mix should be considered.

Controlled

The once easier controlled weeds, such as fumitory, groundsel and even some chickweed, are now surviving in some fields and need to be tackled in some situations. The addition of one litre of Chlorothalonil plus 0.5 litres of Morpholine to crops at or near ground cover will allow up to 10 days disease cover before a main fungicide is required.

Top dressing should now be considered particularly if rain comes. For malting barley crops, the talk this year is to look at applying nitrogen later than previously to increase protein levels. Malting barley growers will know from the last few years' experience that proteins have tended to be on the low side.

Late applications of nitrogen will increase protein levels but I would urge caution as, for many years, the major problem for malting barley was proteins being too high. Do not delay your last top dressing too long unless you are on particularly light land that has a long history of low proteins.

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The drought of the last few weeks has not had the same effect on the winter crops with much winter wheat now past growth stage (gs) 32. These crops should now (if not already done) receive their T1 fungicide. This should include a Prothiconazole mix and this year, in particular, you should also include either Talius or Flexity for mildew.

Products

Many of the winter barley crops are at flag-leaf stage and are at the latest stage for any growth regulation or wild oat control. Barley has only attained half its height by gs 39 so the addition of Cerone or Terpal (latest stage first awns visible gs 39) may be warranted with the T2. One of the new products Bontima, Siltra, Venture Extra or Cauldron might be considered.

Winter rape is in full flower at this stage and again is up to two weeks ahead of normal. These crops should be monitored for pollen beetle and seed weevils at a later stage when pods are set. Insecticide spraying of this crop should be avoided when the crop is in full flower.

While the acreage of fodder beet has reduced again this year, it is still a significant crop in the south-east region. The harsh dry weather of the last two weeks has inhibited weed control of this crop.

The first weed control programme should contain Debut plus Venzar or Goltix plus Betanal Expert and vegetable oil. The rate of Betanal and oil should vary depending on the size of the weeds.

If conditions remain harsh, split the T1 application into two half rates, with the first application followed five days later by the second application. This is kinder on crops and works well.

Pat Minnock is based in Carlow and is the president of the ACA and a member of the ITCA. Email: www.minnockagri.ie

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