Spraying success is all about attention to detail

10 Nov 2017
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Photo: Chris O'Donnell, University of Queensland

One size doesn’t fit all when it comes to implementing effective vineyard spraying regimes, but Dr Andrew Hewitt is confident there are solutions for all.

That’s one of the positive messages to come out of a recently completed three-year project he led at the University of Queensland (UQ). The other is that the ‘solution’ won’t necessarily cost a lot.

‘One thing that surprised us was the old axial air blast sprayer, which is still the most popular one in the wine industry according to the survey we carried out before starting work’, Dr Hewitt said.

‘It can be awful for missing the target because it is spraying from the ground up, but doing something as basic as putting a tower at the top to force the spray back down made it one of the best.

‘So, you don’t have to go out and buy a new piece of equipment; you can make a simple change to improve an old piece of equipment. Bigger companies might want to invest in the best, but there are alternatives.’

Dr Hewitt has a lot of data on what those alternatives are and has been providing advice at workshops around the country. His goal now is to create a spray calculator that viticulturists can use to develop an approach tailored to their circumstances.

With colleagues in UQ’s School of Agriculture and Food Sciences he already has developed a version for the grains industry and has received funding to turn a simple spreadsheet into an app. However, that next stage – and the development of a wine sector version – is on hold while the Australian Pesticides and Veterinary Medicines Authority (APVMA) develops new national regulations covering spray drift.

‘The wine sector calculator will cover how to get good spray coverage without drift and we want it to tie in with the regulations so it will have teeth. The way you bring change in spray drift is a combination of regulation and incentive and technologies and education.’

- Dr Andrew Hewitt, University of Queensland

The calculator will allow growers to adapt the generic requirements set out on chemical labels in relation to buffer zones based on their situation: what’s around them, the sprayer they are using, their dosing rates and whether any barriers are in place. ‘All the things that were in our project will tie into the tool’, Dr Hewitt said.

The project was funded by Wine Australia with the timing of the APVMA’s review in mind, but the issue itself has been around for a long time: how to get good spray coverage in the vineyard at all times of the year.

Studies were conducted in wind tunnels and vineyards to show the performance of factors that affect spray coverage and losses through runoff and drift, including different combinations of nozzles, adjuvants, electrostatic charging, recapture systems, air targeting, barrier vegetation and netting.

And the answer? The best system for any given application will depend on the target.

For example, for herbicide applications, coarser sprays can be used, whereas for foliar-applied sprays, the finer sprays can be optimally directed to their target, including inner canopy areas, using lateral air or radial air with deflector air at the top.

Recapture-recycling sprayers offer an additional benefit to those listed above in that the small amount of spray that misses the target is caught and can be reused, reducing losses to almost zero. Electrostatically-charged sprays offer excellent coverage on all leaf surfaces but can drift under adverse conditions due to the very small size of the droplets.

The project’s final report online here.