Effects of Chlormequat, Girdling, and Tipping on Berry Set in Vitis vinifera L

Abstract

Chlormequat (CCC, Cycocel^TM) at 700 mg/L a.i., applied one week before capfall, and girdling of trunks of vines at a similar time increased bunch weight and yield of Pinot noir in Canterbury, New Zealand. Responses to the two treatments were similar. A high-yielding (10/5) and a low-yielding (D5V12) clone of Pinot noir were investigated. The responses were much greater in the latter, where yields were doubled. Tipping shoots one week before capfall caused a small but not significant increase. Girdling and CCC increased the number of bunches with shrivelled berries. Although treated bunches were tighter, no increased disease incidence was recorded. Chlormequat and tipping increased fruit production on lateral shoots (second crop), while girdling tended to reduce it. Chardonnay in another district (Polk County, OR) also responded to girdling by yield increases of up to 100%; however, in this wetter climate, increased disease and lower °Brix were recorded. Chlormequat and girdling increased the number of seedless grapes. This effect of girdling is consistent with the literature, but that of CCC is not, since it has been previously reported to increase only seeded berries.