Overview
The report is a background knowledge source on sunburn of winegrapes and its prevention. Demonstration sites in three Queensland regions compared leaf thinning, shoot thinning, sprawl, bird netting and sunscreen sprays on Chardonnay and Shiraz in the hot 2009/10 season. Fruit zone leaf thinning increased bunch zone light and UV radiation, causing sunburn, more brown pigments in Chardonnay and lower anthocyanins in Shiraz, while overhead canopy protected fruit. The report advised against leaf thinning and shoot thinning in hot seasons, although severe weather limited firm conclusions. A significant amount of research has been conducted on this subject since publication; refer to more recent published research and other Wine Australia resources.
Demonstration sites were established in Queensland’s Granite Belt, South Burnett and Scenic Rim regions to illustrate the impacts of canopy management options on exposure of Chardonnay and Shiraz over the 2009/10 vintage. Demonstrated options included sprawl, VSP, fruit zone leaf removal at pea size and véraison (easterly or both sides of canopy), bird netting, or commercial sunscreen products (calcium carbonate or kaolin clay). Differences in fruit exposure, grape and wine quality were noted. Growers inspected the demonstration sites prior to harvest and provided feedback on fruit quality. Fruit was harvested, analysed and wines made and analysed, and results presented and discussed at the 2010 Queensland Viticulture Seminar. At this seminar / workshop, industry participants were also able to conduct sensory evaluation of the wines to determine any impacts of alternative management practices on wines produced, to supplement their evaluation of fruit quality prior to harvest.
Conclusions from this project were confounded by problematic seasonal conditions with diverse severe events including frost, hail, heat and water stress and fungal disease pressures. Differences were noted in exposure and sunburn of the Chardonnay grapes prior to harvest, although only marginal differences were seen in the measures of fruit and wine quality of either variety. We are wary of making inferences from this study over a difficult season where site and seasonal factors confounded differences due to imposed management practices.
Abstract
While Queensland wine industry development has relied upon adoption of viticultural practices from established winegrowing regions, such procedures are not necessarily best practice under local conditions. Demonstration sites were set up to show the impacts of canopy management options on exposure of Chardonnay and Shiraz over the 2009/10 vintage in the Granite Belt, South Burnett and Scenic Rim.
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