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Saturday 25 November 2017

Aphicide resistance in UK is a timely warning

DISEASE PRESSURE: Mildew on the winter barley Cassia, which was sown on September 20
DISEASE PRESSURE: Mildew on the winter barley Cassia, which was sown on September 20

Patrick J Phelan

Crops were sown into lovely seedbeds this autumn, resulting in good plant establishment and plenty of optimism. That said, establishment of cereal volunteers has been phenomenal in fields which were not grubbed prior to sowing.

Volunteers have brought all the problems associated with the "green bridge" – aphids, mildew and rhyncosporium in barley.

Seeding rates should be increased from now on to allow for poorer seedbeds. Both wheat and oats should have a minimum seeding rate of 350 seeds/sqm.

Lower temperatures and wetter soil conditions will result in slow emergence of crops sown recently and will give a longer period for slug damage. Crops sown after oilseed rape or where a lot of trash was present in the field are particularity at risk.

Slug pellets will control mature slugs that are feeding but may miss juvenile slugs so repeat applications are likely to be necessary if moist mild conditions occur.

Cooler weather will slow down aphid migration but periods of milder weather will allow further invasions.

Continue to monitor crops carefully and spray if aphids are found.

In most years, a final aphicide application in early November will provide control for the remainder of the year. However, guidance on the need for later applications will be available from our monitoring of ITCA aphid traps.

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RESISTANCE

Resistance in Britain to the principal contact aphicides (pyrethroids) is a timely warning for us to implement best practice when using pesticides.

Check fields within a week of spraying pytethroids and, if aphids are found, spray with approved chlorpyrifos products such as Dursban, Trigger, Barclay Clinch XL.

Ideally there should be an interval of two and preferably five weeks between ploughing and sowing a cereal crop, so as to reduce risk of aphid survival within the field.

Application of Glyphosate to stubbles or grass before sowing will reduce risk.

Ploughing down this year's lush volunteers and sowing after a short interval presents a real risk.

Aphids can feed directly on the new crop's roots without ever appearing above soil. This causes Barley Yellow Dwarf Virus (BYDV) transmission.

While there is a considerable amount of winter barley sown, and less wheat in some areas, there is a temptation to consider ploughing additional grassland.

However, Nitrate Regulations prohibit ploughing of grassland from October 16 to November 30. You must therefore wait until December 1 to plough again.

Check your most recent soil analysis reports to plan what soil sampling should be done this winter. If samples are more than three years old, you should resample now and plan to correct nutrient deficiencies.

Many farmers have allowed fertility levels to drop in recent years. Current analysis reports and recommendations will put you in a better position to ensure that nutrient applications will be tailored to the specific needs of your land.

Applying nutrients that are already in adequate supply will do little to compensate for other deficient nutrients. So applying phosphorus to land which is short of lime or potash will do little to improve yield.

The long dark evenings give you little excuse for not tackling your paperwork. Finalise the fertiliser and pesticide records for 2013.

Check your chemical store to ensure that all products have an in-date PSC number. If you have a product which is beyond its permitted use period, you must make arrangements for collection by an authorised disposal company.

PESTICIDES

The EPA , Department of Agriculture and Teagasc are currently finalising arrangements for a number of 'bring centres', similar to what is done for silage wrap, to which farmers will be invited to deliver pesticides which are no longer approved, spent veterinary products etc for a nominal fee.

This will be a great opportunity to clear all obsolete chemicals from farms. Each bring centre will only be open for one day so watch out for your local date in the media.

Patrick J Phelan is a member of ACA and ITCA. Email: pj.phelan@itca.ie

Irish Independent