Leaf removal to regulate fruit ripening in Cabernet-Sauvignon

Aim: Under the effects of climate change it is becoming increasingly common to observe excessively fast sugar accumulation while anthocyanin and flavour development are lagging behind. Understanding the impact of different leaf removal techniques on ripening will provide vineyard managers with a canopy management strategy suitable for regulating sugar accumulation, phenolic maturity and flavour ripeness, thereby helping to mitigate these negative effects. The aim of this research was to quantify the impacts of three different leaf removal techniques on the canopy architecture and ripening of Cabernet Sauvignon.

Methods and Results: Treatments were performed at veraison (~14 °Brix) and included: i) Control, ii) Leaf plucking around the bunches iii) Leaf plucking the top two thirds of shoots apical to the bunches, and iv) Shoot trimming. On the date of harvest no significant difference in grape TSS was observed between treatments. Other results including the effect of the treatments on acidity, anthocyanins, phenolics, and tannins were somewhat inconclusive.

Conclusions:

While various other studies have shown the potential to achieve slower grape sugar accumulation without affecting the concentration of anthocyanins, phenolics, and tannins, the results of this study do not indicate a decrease in the rate of grape sugar accumulation as a result of the investigated defoliation techniques.

Significance and Impact of the Study: Given the cost of implementing these treatments the results of this study do not support the use of these methods for the purpose of delaying fruit ripening in a hot Australian climate.