The use of ethephon in advancing red colour in the apple cultivar Tydeman Early

Abstract

A trial in the Huon Valley of southern Tasmania in 1976 showed that ethephon sprays applied seven days prior to harvest strongly advanced the red colouration of the apple cultivar Tydeman Early. Urea sprayed with the ethephon did not have a synergistic effect on apple colour as suggested for other types of fruit. In a second trial in 1977, sprays were applied two, one and zero weeks before the normal date of first picking, and the fruit harvested one week after spraying. At the first harvest the percentages of fruit in the economically important colour category (61-100% red) were 8.5, 39.9, 53.4 and 60.4 in the 0, 100, 200 and 300 ppm ethephon treatments, respectively. The 100 ppm spray was better than the control (P < 0.001), and 200 ppm was better than 100 ppm, (P < 0.05) ;the 300 ppm spray was not significantly better than 200 ppm. The 200 ppm treatment achieved the over 50% target in the high colour category at the first harvest. Even at the third harvest, fruit on unsprayed trees was not red enough for a one-pick harvest. Treatments reduced yield through an increase in windfalls from 12 to 22% as the ethephon concentration increased from 0 to 300 ppm. No effect on mean fruit size was detected. No commercially important quality problems arose during storage although there was a small overall incidence of slight core rots. This work leads to a recommendation that in Tasmania 200 ppm ethephon should be sprayed two weeks prior to the normal first pick, allowing the complete harvest of marketable fruit one week prior to normal first pick. A stop-drop spray such as NAA or 245TP should be sprayed with the ethephon to reduce abscission losses. Storage is recommended as a method of bridging the supply gap between Tydeman Early and mid-season cultivars.