Foliage Removal Effects on 'Shiraz' Grapevines

¹ Department of Agriculture, Viticultural Research Station, Griffith, N.S.W. 2680 Australia.

All the shoots of mature irrigated 'Shiraz' grapevines (Vitis vinifera) were cut back to either 2 or 6 leaves above the distal bunch for 3 consecutive seasons at one of 5 phenological stages: 1) during bunch elongation; 2) beginning of fruit set; 3) first rapid growth of berries; 4) lag phase; and 5) véraison. Each vine was cut back only once each season. Slashing to the 2-leaf level gave a lower berry sugar and skin pigmentation than did the 6-leaf level, which was not different from control vines. Response to treatment time was less consistent. Bunch weights were not altered by any time of treatment whereas bunch numbers per vine were highest on vines treated at bunch elongation. The results are interpreted in terms of relative strengths of the sinks and sources for organic nutrients. It is concluded for 'Shiraz' vines that in general, the 6-leaf treatment is not too severe but the 2-leaf treatment is overly severe, and it is apparent that unslashed vines have more than adequate leaf area.