Off-the-shelf anti-transpirants could offer growers a simple and effective tool to delay fruit ripening and lessen the effects of vintage compression, preliminary results from a new Australian study suggest.
The study – led by principal investigator Darren Fahey – reflect the findings of similar studies conducted overseas and could be a game changer in the fight to mitigate the effects of climate change.
‘Increased drought conditions, higher temperatures and compressed vintages are increasingly the "new normal" in viticulture, so we were interested to see if any off-the-shelf products could manipulate grape ripening while maintaining grape quality parameters.’
– Darren Fahey, Development Officer – Viticulture with the NSW Department of Primary Industries.
The study tested the effects of applying an anti-transpirant at an application rate of 1 per cent on 3 Vitis vinifera cultivars in field conditions across cool, warm, warm/dry, warm/humid and hot growing regions of New South Wales (NSW).
A water-emulsifiable organic concentrate, derived from conifer resin and formulated as a terpenic polymer with the active ingredient di-1-p menthene, was used in the study. When applied, it forms a flexible film surface coating that acts as a physical barrier – reducing water loss from the leaves, bunches and other vine parts, while allowing stomata to stay open.
Darren Fahey testing Pinot Noir anthocyanins
The anti-transpirant was applied as a single treatment at pre-flowering growth stage or pre-veraison growth stage – or at both pre-flowering and pre-veraison. The treated vines were then compared against an untreated control.
Eleven separate field trial sites were established on commercial vineyards across 7 wine growing regions of NSW, beginning in the 2017–18 vintage on Pinot Noir (2 sites), 2018–19 vintage on Shiraz (7 sites) and 2019 on Chardonnay (2 sites).
The key findings of the study included:
- increased berry weight in Shiraz and Pinot Noir grapes (with site playing a factor in Shiraz and evidence of an interaction between the years occurring in Pinot Noir)
- increased bunch weight in Pinot Noir, Shiraz and Chardonnay (the response differed between years with Pinot Noir and between sites with Shiraz)
- reduced Baumé (delayed ripening) in Shiraz and Pinot Noir (although the response differed between site and year)
- reduced Baumé (delayed ripening) in Chardonnay, depending on site
- no overall effect of the treatment on pH, TA, and phenolics (although an interaction between treatment, site and year was detected)
- no overall effect on anthocyanin (although an interaction between treatment and year was detected)
- a decrease in alcohol concentration in both Pinot Noir and Shiraz across different climatic locations, and
- anecdotal evidence for a general reduction in grape shrivel (see image below).
Berry shrivel differences in Pinot Noir grapes at harvest. The bunch on the left is unsprayed.
Mr Fahey said the findings were important for growers.
‘Vintage compression leads to many varieties ripening at the same time, resulting in higher sugar levels, higher pH and lower TA of harvested fruit and placing winery logistics and capacity at the limits of production to uphold fruit quality.’
‘I often hear comments like "The fruit was fine on Friday, but by Monday has lost all it's attractiveness". So, knowing that we can manipulate this through a simple anti-transpirant application may prove beneficial for the sector in the future.’
‘The anti-transpirant used in the study provided increased yield based on berry and bunch weights across two drought-declared years in NSW.’
– Darren Fahey.
Darren said further long-term research across several seasons was required to assess the full potential and benefit of anti-transpirant use. A detailed report on the 2017–18 season can be found here and results will also be presented at the Australian Wine Industry Technical Conference later in July 2019.
The research was funded by the NSW Department of Primary Industries, Skills Development Program and Wine Australia.