Effects of ethephon on cluster loosening and berry composition of four wine grape cultivars

SummaryPre-harvest sprays of ethephon loosened clusters and berries of the four grape cvs Riesling, Trebbiano, Ondenc and Sultana, and resulted in more complete fruit recovery by shaking compared with controls. Ethephon’s effects were influenced by concentration, time of treatment, cultivar differences and seasonal conditions. Concentrations of 1 000 ppm or above were more effective than lower concentrations in reducing the pull force required to detach the cluster in five to seven days. Cv Sultana gave the highest fruit recovery in the first season and was the only cultivar which responded to ethephon in both seasons, although the response was less in the second season. On a weight basis ethephon at 2 000 ppm removed 94%, 79%, 85% and 70% of the clusters of cvs Sultana, Riesling, Trebbiano and Ondenc respectively. Some defoliation was observed at 500 ppm ethephon and above, increasing with greater concentration over the first 10-14 days but with no later effects. No canes were killed or disbudded but natural defoliation in autumn was accelerated by about two weeks.