Effects of Gibberellin Treatments on Ripening and Berry Drop from Thompson Seedless Grapes

Berry drop from Thompson Seedless bunches during and after harvesting is a well-known phenomenon. It causes difficulties in marketing and can significantly reduce growers income. The reason for berry drop is known to be the GA3 treatments applied to achieve the required berry weight. During the past seven years, the reasons for berry drop were sought and the main one was found to be the later applications of GA3 as related to the physiological stage of the berry development. The total amount of GA3 given or the concentration of GA3 at each application had a much smaller effect on the rate of berry drop. The same was true for delay in ripening. Application of 4-CPA further delayed ripening but reduced berry drop significantly.