Effects of Low Ethephon Concentrations on Quality of ‘McIntosh’ Apples1

Red color development of ‘McIntosh’ apples that previously received a mid-July application of succinic acid 2,2-dimethylhydrazide (SADH) and were then treated before harvest with 2-chloroethylphosphonic acid (ethephon) occurred earlier and more extensively than on controls. Fruit receiving 150 or 250 ppm ethephon were less firm within 7 or 8 days than fruit receiving only SADH. The respiratory climacteric was advanced 6 to 10 days by ethephon treatments as low as 25 ppm. Naphthaleneacetic acid (NAA) was less effective than 2,4,5-trichlorophenoxypropionic acid (fenoprop) in preventing preharvest drop, especially at higher ethephon concentrations. Fruit from all treatments kept well in both CA and air storage provided they were in good condition at harvest. Scald developed to a greater extent on stored fruit that had received ethephon than on controls.