Selecting the right nozzle type is key to getting the most effective potato haulm destruction from desiccants this pre-harvest season, with up to 45% improved desiccation dependent on nozzle choice.

Research carried out by chemical firm Certis Belchim has built-up a strong dataset on best practice use, trialing two separate nozzles and whether a pre-flail treatment could speed up skin set and stolon detachment ahead of harvest.

The trial tested two nozzles: a standard flat-fan and an air induction twin flat-fan nozzle with forward and backward facing fans, known as the Lechler IDTA nozzle.

The latter is said to improve coverage and offers 90-95% drift reduction over a standard flat fan.

See also: Can maincrop potatoes be grown in a regenerative system?

The trial

Two applications of the PPO-inhibitor Gozai (pyraflufen-ethyl) plus Toil (95% methylated rapeseed adjuvant oil) were made in 300 litres/ha of water: T1 on 6 September and T2 on 13 September.

One week after the first application, the plots treated with the Lechler nozzle improved the level of leaf desiccation by 45% and Gozai’s activity on the stems by 20%, explains Certis Belchim’s technical account manager Jeremy Booth.

“Using the backwards and forward twin fan nozzle will achieve the outcome you want much quicker than the standard,” he says.

Pre-flail treatment

“On the benefit of a pre-flail treatment, it increased the speed of skin set and stolon detachment, and could be a useful application in some seasons,” continues Jeremy.

With desiccation programmes starting, he added that, aside from nozzle choice, crop and environmental conditions at application have a big influence on speed of kill.

High UV light intensity helps improve activity of PPO-inhibitors like Gozai, so spraying at the start of a sunny day is best and if flailing, 15-20cm of stem should be left above ground to aid kill.

“Previous work has also highlighted the importance of water rate and we see that 300 litres/ha balances consistent results with sprayer efficiency,” says Jeremy.

With reports of foliar late blight infection in crops this season, he stressed the importance of maintaining disease protection until all foliage is dead.

“We support the recommendation of Gozai + Toil with our blight fungicide Ranman Top (cyazofamid).

“Ranman Top offers good protection of both foliar and tuber blight, which is crucial at the backend of the season.”