WA growers continue extreme heat and wind trial
A sunscreen and shade trial is continuing to deliver results for Western Australian grapegrowers.
The project, being conducted as part of the Western Australia Regional Program funded by Wine Australia, started in 2014 to help growers find ways to manage the effect of extreme heat events on fruit quality – in particular, looking at the use of shadecloth and two commercially available sunscreen products.
Based at Howard Park Wine’s Leston Vineyard in Margaret River and managed by chief viticulturist David Botting, the trial has been extended for another 12 months but will focus on applying just one sunscreen product (Surround) and the pull-up shadecloth.
Mr Botting said despite the lack of extreme heat or wind events during the 2014–15 growing season, the trial provided some great insights into managing UV exposure.
‘Sun exposure is crucial to fruit ripening and development but as we strive to achieve more sun exposure, the fruit becomes more vulnerable to extreme heat events’, he said.
‘It’s exacerbated in the Margaret River region where the vines are predominately planted in a north-south direction with the western face being overly exposed to the effects of the afternoon sun.
‘Extended UV exposure can still cause degraded bloom, skin damage and berry desiccation – even without the extreme heat events or heat spikes the region has experienced in each of the previous four seasons. The trial has allowed us to identify these exposure issues and learn more about managing and hopefully minimising their effects.
‘We’ll also take another look at the wines we made from the trial site last year, 12 months on, so we can see how the treatments and exposure effects play out in the wine’s sensory profile.’
First year trial results showed that the use of kaolin spray-on products (Surround and Screen Duo) reduced damage to exposed bunches by 40–50 per cent and shadecloth applied to cane- and spur-pruned vines reduced damage to near zero.
An additional trial treatment on a partially vertical shoot positioned (VSP) trellis also gave similar protection to the sunscreen spray-on products, as did east–west positioning rather than north–south row orientation.
Cabernet hang-time
A new 12-month trial investigating the effects and costs of extended hang-time on Cabernet vines will begin as part of the WA Regional Program in 2015–16.
Wines of Western Australia Technical Committee Chairman Jim Campbell-Clause (AHA Viticulture) said a trial site in Margaret River had now been selected but the real trial work wouldn’t get started until late vintage.
‘Margaret River Cabernet has clearly become a much-valued variety and, as such, high quality Cabernet grapes are in high demand – but producing the quality level wineries are after can come with some pretty high input costs for growers’, Mr Campbell-Clause said.
‘It can often also mean that wineries want growers to hang their fruit for longer than growers might necessarily want to.
‘Studies in California have shown that an extra two or three week hang-time at the peak of vintage can mean a 30 per cent weight loss – that’s a potential 30 per cent drop in income for growers who earn per tonne.’
The project site has been set up to run three different treatments applying the same management methods but harvesting at low, medium and high Baumé. The trial at the Howard Park, Margaret River Vineyard is being led by David Kelly of Curtin University.
‘Ideally, it will go some way to helping explain the outcomes that wineries are seeking with longer hang-times, as well as demonstrate the effect longer hang-times can have on vines and tonnage for this region. We also want to see how these decisions play out in overall wine quality – and what sort of hang-times are needed to get the quality that wineries are seeking’, he said.
‘We are keen to improve the decisions on when harvest is called for both growers and winemakers.’
Tempranillo management
The third and final project, funded as part of the Regional Program, is helping WA’s Geographe region to secure the future of Tempranillo as a variety of prominence.
Led by Mr Campbell-Clause, the Tempranillo management project will focus on crop load and time of pruning as key priorities as it enters its second vintage.
‘The Geographe region continues to have some real success in local and state shows – against other regional varieties and wines from other states’, he said.
‘Tempranillo’s clearly well-suited to the Geographe and wider WA regions, so there’s a real impetus to get the right growing and management practices in place to ensure we continue to grow quality fruit, in the most cost-effective way.
‘But it’s still really early days for this particular variety here, so there’s a lot to discover and learn about which management practices elicit the best results.’
Last year’s trial investigated crop load, time of pruning and vigour management (using sacrificial canes).
‘Contrary to the expected reduction in vigour through the use of sacrificial canes, the vines appeared to compensate and yield and quality parameters were much the same for the treatments with and without sacrificial canes’, he said.
This year, the project will continue to trial early pruning (during full dormancy in July) and late pruning (just after budburst). The results from the early and late pruning trial last season were not significantly different even though the late pruned vines looked to be more uniform.
‘This season the early pruning was earlier and the late pruning later than last season, so we expect to see a greater influence on fruit quality’, he said.
‘We’ll also investigate the effect of light crop loads on final bunch and berry size and quality. This season we plan to repeat the process but with slightly higher crop loads.’
‘We also entered some of the wines made from the trial sites by Richard Fennessy (DAFWA) into the Geographe Wine Show earlier this year. The judges’ comments suggested that the wine made from the vines with low crop load (4t/ha) were darker, more complex and had greater density than those made from heavier cropping vines (6t/ha and 10t/ha).’