Flag leaf application: make more from your fungicide

Article taken from the Agronomist & Arable Farmer

Using bespoke application equipment we are able to mimic grower’s application criteria but also:

  • operate with small amounts of test material;
  • operate at farm speeds up to 16 km/h and over;
  • have the ability to change nozzle types;
  • have the ability to change nozzle direction and configuration to examine drift and efficacy;
  • be able to conduct replicated trials.

 
Some of the results have contradicted conclusions inferred from nozzle characteristics or formulation type of a fungicide – illustrating the importance of field testing.

Water volume

Between 2009 and 2011 the impact of water volume was investigated in 12 trials where yellow rust was the main pathogen.  Reducing water volume from 200l/ha to 100l/ha resulted in improved disease control and on average an extra 0.24t/ha yield.  In high disease situations the difference was up to 0.8 t/ha.  In the higher septoria season of 2012, results suggested an advantage of applying T2 fungicides in 200l/ha.

Nozzle choice

Flat-fan nozzles (F110-03) have equalled or outperformed the performance of air inclusion nozzles (BBJ-03) in 42 out of 45 trials.  The average benefit from using flat-fan nozzles was 0.35t/ha.  According to the HGCA, the Hypro Guardian Air 03 has a slightly finer spray quality than the BFS Billericay Bubblejet 03.  However in our trials, bubblejet nozzles have consistently performed better (average increase in yield + 0.6t/ha).

Nozzle angling

Angling of nozzles (30°) using nozzle caps has been investigated in 43 trials.  By placing water sensitive paper in the canopy we have seen that angling does not necessarily improve leaf coverage, but increases the number of droplets per cm².  Angling also tends to get spray further down the canopy, which is important for yellow rust control.

With flat-fan nozzles there is a yield advantage from angling in high disease (yellow rust situations), with yield increases of around 0.5t/ha possible.  There appears to be a benefit from angling bubblejets in high and lower disease situations (average + 0.24 t/ha).

Where disease pressure is high there is a further yield advantage by angling flat-fan or bubblejet nozzles alternately down and forwards 30°. (this is the same configuration that works best with Atlantis-type treatments against black-grass).

By means of contrast, however, we have seen little improvement in yield with twin nozzles.  Despite an advantage with flat-fan nozzles, we do not always recommend their use.  Fungicide timing trials have shown that application timing can have a massive influence on wheat yield with even the best fungicide treatments.

Sometimes use of an air inclusion nozzle will be necessary to help ensure correct timing so how can we improve the performance of air inclusion nozzles?  In a number of trials we have seen that air inclusion nozzles perform better when used at 4 bar spray pressure (as opposed to 3 bar used in most situations).  Conversely they have performed poorly at low (2 bar) pressure.  In this country and in European registration trials, the adjuvant Velocity as an application aid has consistently improved disease control and yield with all nozzle types.  Velocity contains organosilicone (to improve leaf coverage (and rapeseed fatty esters (which help improve uptake of fungicide into or through the leaf wax layer.

From our extensive trials we would suggest the following for T2 application on winter wheat:

  • 100l/ha water volume (check all the tank mix partners can be used in reduced water volume)
  • Use of flat-fan nozzles – but consider Billericay Bubblejets if conditions are marginal
  • Angle nozzles using nozzle caps (alternate down and forward 30°)
    • In all cases with air inclusion nozzles
    • If high disease pressure with flat-fan nozzles
  • Consider use of Velocity as an application aid, particularly if using air inclusion nozzles.

 

06 June 2014

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