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Wednesday 7 December 2016

Calibrate and reduce speed to improve spraying

Patrick J Phelan

Published 26/04/2011 | 05:00

If you find more than a 10pc variation from the manufacturers' rated output in individual nozzle output across the boom when you are calibrating your sprayer, change individual nozzles
If you find more than a 10pc variation from the manufacturers' rated output in individual nozzle output across the boom when you are calibrating your sprayer, change individual nozzles

Drying winds and high temperatures made for difficult spraying for some farmers last week.

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Ideally, you should spray when growing conditions are perfect -- warm, humid conditions which will give maximum uptake of both fungicides and herbicides. Crops, and indeed weeds, under stress are less likely to take in chemicals. Rates may need to be increased and adjuvants included.

On examination, winter crops that were sprayed over the past few weeks revealed variations of efficacy within fields. Some of this is certainly due to the operator. Wider booms are subject to a greater degree of boom bounce, resulting in variable results in the centres between tramlines. This can be minimised by reducing speed but less speed will mean less acres covered per day, which could prove expensive. Maintaining sprayer suspensions and possibly reducing tyre pressures may also help.

Continue to calibrate sprayers, and if you find more than a 10pc variation from the manufacturers' rated output in individual nozzle output across the boom, change individual nozzles. If you find more than a 10pc variation, change the entire set. Low drift nozzles are of benefit when spraying under poor conditions. In general, boom height should be 50cm over the spray target, and use higher volumes (200l+/ha) of water when you need to get chemicals into the crop.

Wild oats have been very slow to appear but a lot have germinated in the past week, perhaps with more to come. Control in both wheat and barley is with Pinaxoden (Axial, Avena or Axis). Fenoxaprop -- P -- Ethyl (Cheetah Extra or Fencer P) is for use on wheat only.

Most winter wheat crops are now past growth stage (gs) 31, the latest stage suitable for CCC. Ceraide and Meteor may be used up to gs32. Crops past gs32 may get Moddus, Cerone or Terepal.

I haven't ever seen crops with so few disease symptoms in late April. However, septoria tritici is evident in all crops; eyespot in some and Lion has mildew.

All crops should get their T1 this week, if not already applied. Chlorothanonil with Fandango, Coyote or Proline + Strob will be the product of choice in some situations; products containing epoxiconazole, such as Venture Extra and Cauldron, will be preferred in other situations, as will Gleam, which has less control on eyespot.

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Straight epoxiconazole with Chlorothanonil will be the cheapest option but, similar to Gleam, it provides very little protection from eyespot.

Winter barley is moving very rapidly through the growth stages, with many crops now at gs37 and some crops at gs49 (first awns visable), which is the cut off point for the application of growth regulators. Crops are generally free of disease symptoms with the exception of some crops in coastal areas, which have considerable levels of rhyncosporium. All crops should get a robust rate of triazole this coming week. Options for this application include Cauldron, Siltra, Bomtima Venture Extra, Fandango, Coyote, Proline, Lumen and Allegro Plus.

Winter oats are scarce in Tipperary due to winter kill. However, for those who have winter oats, gs32 is the time to apply the main growth regulator. This should be combined with a triazole and a morpholine. Talius is very effective for mildew prevention. Corbel should be included where mildew is present. Tocata has proven to be very effective.

A lot of the spring cereals are now at the ideal stage for weed control -- open cereal canopy with a large flush of weeds present. Nearly all crops should be sprayed this week with a sulphonyl urea, combined with a tank mix partner such as CMPP, Starane, GalaxySwipe P Oxytril or Stellox. Your choice of herbicide will be determined by the range of weeds present and preferably should be different to last year to minimise risk of allowing resistant weed populations to build up.

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

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