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Thursday 23 November 2017

Tillage advice: Spring crops are under severe stress

Oil-seed Rape crop
Oil-seed Rape crop
Pat Minnock

Pat Minnock

The harsh, cold dry weather up to the end of April restricted crop growth and development and while winter crops had been well advanced at the time this weather has brought crops back to their more normal stage of growth for this time of the year.

The April weather restricted spraying in many cases. There is some evidence of spray damage around the country where spraying took place during this cold period.

However, it is always better to hold off on spraying until there is good growth and no frosts forecast. You can generally be happy in the knowledge that if growth conditions are poor crops are not moving through stages so there is less likelihood of correct timings being missed, which is always a concern. There is also no doubt that spraying crops that are under pressure is likely to lead to more damage.

Weather last week continued to remain cool and very dry and spring crops, in particular, are under severe stress. Last week also provided the first significant evidence of barley yellow dwarf virus (BYDV) in winter crops. I came across serious damage in east Wicklow, which is generally seven to 10 days ahead of growth more inland. The levels of BYDV especially in early-sown crops is significant and worrying. Awns have begun to appear in most winter barley crops.

It is now too late for any further growth regulation. Crops are generally clean and with awns emerging many may be considering the final fungicide. However, with 10 or 11 weeks to go to harvest it is possibly too early to expect this spray to keep this crop clean until then. The more backward crops, if still at flag leaf, could benefit from a growth regulator especially if these crops are strong. The final spray should include a triazole plus a strob with or without a SDHI. Always include chlorothalonil in the mix.

All winter wheat crops should have received their T1 fungicide by now. It is still generally too early for T2s but rust should be monitored in all crops especially down south where there are reports of the disease appearing.

Many winter oat crops were due to get their main growth regulation towards the end of April. In many cases this was postponed due to the weather and from previous experience. It is likely that much of this growth regulation on oats was completed last week during the spell of good weather. If not, and as most winter oat crops are now likely past growth stage 32/33, options for further growth regulation are limited. The new Meddax Max which can be used on winter oats up to growth stage 39 is probably now the last option.

Spring crops are now at the ideal growth stage (15 to 22) for herbicide treatment but spraying should be avoided until growth conditions improve. There is an amazing range of herbicides now available for this task with more new products launched again for this season.

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All the standard sulphonyl urea (SU) mixes or various combinations are available so it is worthwhile shopping around to get value for money.

These need a mixer to control some of the more difficult weeds or weeds not controlled by SUs. Typical mixer products would be Galaxy, Fluroxypyr products or even a number of the cheaper hormonal products such as Dicamba/MCPA/CMPP mixes.

The use of a product like Hussar on barley or wheat gives excellent control of annual meadow grass and can suppress wild oats. There are a wide range of product combinations which can suit every situation and pocket if chosen wisely. Growers need to be aware if they have resistant weeds. Was your weed control poor last year?

The number of weeds becoming resistant to aceto-lactase synthase (ALS) inhibiting herbicides (eg Ally Max) are growing. A new product like Pixxaro can play an important role in controlling resistant weeds, such as chickweed and poppy and also gives good control of many other weeds like cleavers, bindweed, pale persicaria, ivy leaved speedwell and fat hen. However, it is weak on charlock, volunteer rape and mayweed.

The partner chosen is important and should be decided on based on the weeds present or on the field weed history. Watch and record the PCS number of all chemicals used from the can. Do not depend on PCS numbers on invoices or from the PCS website.

All top dressing should be completed on all crops at this stage with spring barley brought to approx. 135kg per hectare of nitrogen. An extra 20 kg N per hectare can be used if yields justify. Late applications of N to malting barley will lead to higher proteins and may lead to rejections so this must be considered.

Crops of winter oil seed rape, which have brightened up the countryside over the last few months are coming to the end of their flowering. These should be monitored for the presence of weevils and sclerotinia. A final spray of Filan could be considered if rape is grown in close rotations and the chances of sclerotinia is high.

Fodder beet is now generally ready for its first herbicide which should be a mixture of Debut and Betanal Maxxpro plus Venzar or Goltix - depending on the weed spectrum. The addition of a vegetable oil will improve control especially where weeds are getting stronger. It is worth recording that currently Seed Technology Waterford are monitoring and carrying out assessments of the bean seed weevil on crops throughout the country.

These have been monitored weekly over the last five or six weeks to determine the numbers and likely resistance to pyrethroids in the population. To date threshold levels have not been breached in most of the country except for parts of the south, particularly Cork, where treatment is recommended.

Pat Minnock is a Carlow based agricultural consultant and a member of the ACA and the ITCA. www.minnockagri.ie


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