Viticulture

Leaf strip timing can reduce sunburn in grapes

By Country News

Research by the National Wine and Grape Industry Centre has discovered the ideal time to remove leaves from grapevines.

Postdoctoral researcher Dr Joanna Gambetta from Charles Sturt University studied the impact of timing defoliation in reducing sunburn in grapes.

Dr Gambetta found early leaf removal led to a higher accumulation of photo-protective compounds in the grapes earlier in the season, allowing them to adjust to hotter conditions and reducing the incidence of sunburn.

“Sunburn can affect up to 15 per cent of wine grape berries in Australia in any given season as a result of high light in combination with high ambient temperatures and UV radiation,” Dr Gambetta said.

“This can lead to downgraded fruit causing significant economic losses to growers and wineries.”

The study’s key findings were:

¦ Leaf removal led to higher final concentrations of all photoprotective compounds when compared to the non-defoliated control;

¦ Marked differences were observed in the accumulation patterns of the photoprotective compounds between berries defoliated early (end of flowering) and those defoliated later (véraison);

¦ Among all three treatments, sunburn damage was higher in grapes on vines defoliated at véraison; and

¦ There were no significant differences between yield, total soluble sugars, pH, titratable acidity and yeast assimilable nitrogen between treatments within each vineyard.