Degreening Citrus Fruit with Postharvest Applications of (2-Chloroethyl)phosphonic Acid (Ethephon)1

Abstract

Ethephon2 was applied as a postharvest fruit dip to ‘Bearss’ lemons, ‘Robinson’ and ‘Dancy’ tangerines, ‘Hamlin’ oranges, and ‘Marsh’ grapefruit. Concentration as high as 8,000 ppm were used, and samples were held at 16, 21, and 27°C. Responses differed among cultivars, but were greater and more rapid as the temperature increased. Untreated fruit degreened more completely at 16° than at higher temperatures. At 21 and 27°, degreening usually was maximum with concentrations of 500 to 1,000 ppm. ‘Robinson’ tangerines responded to lower concentrations and showed increasing inhibition at levels from 2,000 to 8,000 ppm ethephon. In tangerines and grapefruit, degreening with ethephon approached that obtained with ethylene. Stem-end rot was increased by ethephon applications. These losses were greatest at the higher concentrations and temperatures, but they were lower and later than from ethylene degreening.

Ethephon-induced Defoliation Patterns and Subsequent Yields in Citrus1

“…Fruit were harvested 7 days after spraying. Because no difference between the 2 dates of application was found, all plots were combined for a single harvest on Oct. 26, 1976. Fruit color responses were determined by transmittance measurements of chlorophyll levels in samples of 2 0 fruit per tree 7 days after spraying (3). Values were reported as the difference in optical densities at 695 and 740 nm (AOD695-740 nm).…”