Late leaf removal does not consistently delay ripeningin semillon in Australia

Abstract

Context and purpose of the study ‐ An advancement of grapevine phenological development has been observed worldwide in the last two decades. In South Australia this phenomenon is even more accentuated since grapevine is often grown in a hot climate. The main consequences are earlier harvests at higher sugar levels which also result in more alcoholic wines. These are deemed undesirable for the Australian wine industry with consumer preferences shifting towards lower alcohol wines. Vineyard practices can be implemented to control and delay ripening. Amongst them, apical late leaf removal has been successfully applied in Europe to delay ripening by up to two weeks in Sangiovese, Aglianico and Riesling. In those studies, no negative effects were observed on grape colour, phenolics and on the carbohydrate storage capacity of the vines. To date, this technique has not been studied in Australia. In this study late leaf removal, apical to the bunch zone was applied to the variety Semillon for four seasons and compared to an untreated control.

Material and methods ‐ The study was carried out for four consecutive seasons starting in 2015 in the variety Semillon at the Waite Campus, University of Adelaide, Australia. Yield, yield components and berry chemistry (total soluble solids, titratable acidity, pH and total phenolics) were all assessed during the study.

Results ‐ Results showed that despite the removal of up to 30% of the vine’s canopy, the technique was effective in delaying ripening only in one of the four seasons. No differences were observed in yield components and berry and wine chemistry between the treated and untreated vines. These results suggest that the technique might not be a feasible strategy to delay ripening in Semillon grown in a hot climate in Australia.