Gibberellic acid is registered and recommended in California for certain uses (particularly in delaying rind and fruit maturity) on navel oranges and lemons. Favorable responses have also been obtained on limes and mandarins, but our present knowledge is insufficient to warrant registration or recommendation for use on these fruits. So far, we do not know how to take advantage of the delayed softening and aging of Valencia orange and grapefruit rind tissue without obtaining considerable regreening. The influence of GA₃ on retention of young fruit has potential value, but no practical method has yet been devised to avoid phytotoxic responses.

Valuable cooperation was also received from farm advisors, growers and packers. This research was supported in part by financial aid from the Navel Orange Administrative Committee; Sunkist Growers; Amdal Co. (a division of Abbott Laboratories); Chas. Plizer & Co., lnc.; Elanco Products Co. (a division of Eli Lilly and Co.), and Merck & Co., Inc.