Use of Ethrel to Stimulate Coloring and Ripening of Minnesota Apple Cultivars

Abstract

Increased red color and early maturation of preharvest 2-chloroethylphosphonic acid (Ethrel) treated apples has been reported frequently (3, 4, 5, 7). However, this early fruit maturity and accelerated red color development has been associated with a hastening of abscission of mature apple fruits (3) and a decrease in firmness of the apple flesh (3, 5, 7). Eclgerton (3) and Unrath (7) reported that 2,4,5 trichlorophenoxypropionic acid (2,4,5-TP) effectively counteracts the promotion of abscission by Ethrel. They also stated that even though a mid-summer application of succinic acid 2,2-dimethyl hydrazide (Alar), 60 to 70 days before harvest, delayed apple abscission, preharvest application of Ethrel effectively overcame this delay. Alar does, however, improve apple flesh firmness (1,2) and delay the appearance of the physiological discolor watercore (2).