Relative Effectiveness of the Mono-, Di-, and Trichlorophenoxyacetic Acids in Retarding Abscission of Mature Apples

• Published in: Botanical gazette (Chicago, Ill.) Ill.), 1955-09, Vol.117 (1), p.51-55
• Main Authors: Marth, Paul C., Preston, William H., Mitchell, John W.
• Format: Article
• Language: English
• Subjects: Abscission; Fruit drop; Fruit trees; Fruits; Harvest date; Physiology; Polysorbates; Tree felling
• ISSN: 0006-8071
• DOI: 10.1086/335890

1. The relative effectiveness of a complete series of highly purified mono-, di-, and trichlorophenoxyacetic acids in retarding the abscission of mature fruits of six varieties of apples was studied. The pentachloro- and one tetrachlorophenoxyacetic acids were also included in the experiment. 2. Each of the sixteen phenoxy compounds was applied at 1% concentration in a carrier composed of one part Tween 20 and four parts lanolin about 3 weeks before the usual harvest date for each variety. A narrow band of each acid mixture was placed at the abscission zone of each of ten tagged fruits on one tree of each variety. 3. 3,4,5-Trichlorophenoxyacetic acid was highly effective in retarding abscission of all six varieties, while 4-chloroand 2,5-dichlorophenoxyacetic acid were highly effective on five varieties. Four acids, 3-chloro-, 3,4-dichloro-, 2,3,4-trichloro-, and 2,4,5-trichloro-, were highly effective on four of the six varieties. Abscission of two varieties was effectively retarded by 2,4-D, while only one variety responded well to application of 2-chloro-. 4. The compound 2,3,5-trichloro- had a mild retarding effect on the abscission of all six varieties, but fruits treated with the compounds 2,3-dichloro-, 2,6-dichloro-, 3,5-dichloro-, 2,3,6-trichloro-, 2,4,6-trichloro-, 2,3,4,6-tetrachloro-, and pentachlorophenoxyacetic acids fell from the trees at about the same rate as the controls.