Spring Spraying

Spray nozzle choice for fungicide applications

A small droplet air induction nozzle remains the nozzle of choice for fungicide applications from growth stage 24 (GS24) onwards, HGCA-funded work has concluded.

The three-year project, which came to a close at the end of 2011, was conducted by Silsoe Spray Application Unit at NIAB TAG and sought to determine how application techniques can improve spray distribution within a cereal crop canopy.

Field experiments were carried out to investigate the influence on spray distribution of water volume and nozzle design and wind tunnel experiments evaluated any potential effect of wind speed.

A range of nozzle designs were used, including conventional flat fans with fan angles between 80 and 120 degrees and small droplet air induction nozzles such as the Billericay Bubble Jet and the Hypro Guardian Air/ Amistar nozzle.

Spray volumes tested ranged from 100 to 400 litres per hectare, with the higher volumes achieved by doubling nozzle size and reducing forward speed.

A small droplet air induction nozzle is appropriate from GS24 onwards

Clare Butler Ellis

Increasing water volume has no influence on the quantity of active ingredient reaching the lower part of the crop canopy. In addition, the field trials results showed the deposit on the whole plant was significantly lower with the highest volume and largest droplets.

Increasing wind speed can compromise spray penetration into a cereal crop canopy with fine sprays. The wind tunnel experiments showed increasing the wind speed reduced the quantity of spray able to reach the bottom of the canopy with a fine spray.

However, the spray from the drift-reducing nozzle used (the Billericay Bubble Jet BFS 025), was unaffected by wind speed.

“In practice this means that using a small droplet air induction nozzle is likely to lead to a more uniform distribution over the crops,” says project leader Dr Clare Butler Ellis, head of Silose Spray Application Unit.

Deposit

Both the Billericay Bubble Jet and the Guardian Air/Amistar nozzles gave improved spray deposit in the lower part of the crop canopy compared to the conventional flat fan nozzle, as did to a lesser extent an 80 degree flat fan nozzle.

“This supports current recommendations in the HGCA nozzle chart that a small droplet air induction nozzle is appropriate for fungicide applications from GS24 onwards and is likely to be the best option if penetration into the base of the canopy is needed,” says Dr Butler Ellis.

“So many labels say increase the volume if you want to get increased spray penetration but that is not the case.

“There may be other reasons for increasing the volume but don’t be tempted to raise the volume just to get to the bottom of the spray canopy as it might be counter-productive, says Dr Butler Ellis.

Key findings

  • Increasing application volume has no influence on the quantity of fungicide active ingredient reaching the lower part of the crop canopy
  • Increasing wind speed can compromise penetration into the crop canopy of fine sprays
  • Using low drift nozzles can be advantageous in many practical situations and small droplet air induction nozzles would be the nozzle of choice

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