Control of Ripening in ‘McIntosh’ Apples I. Some Growth Regulator Effects on Preharvest Drop and Fruit Quality at Four Harvest Dates1,2

in Journal of the American Society for Horticultural Science
Norman E. LooneyAgriculture Canada, Research Station Summerland, British Columbia

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Ethephon (600 ppm applied 3 weeks or 300 ppm applied 1 week ahead of “normal” harvest) combined with either NAA or 10 or 20 ppm 2,4,5-TP increased red color and decreased firmness of fruits harvested 6 or 12 days after each treatment. In neither series did NAA or 2,4,5-TP control drop adequately.

A midsummer treatment with 1000 or 2000 ppm succinic acid-2,2-dimethylhydrazide (SADH) modified these results by enhancing color and firmness and greatly reducing fruit drop relative to fruits treated solely with ethephon-auxin.

Contributor Notes

Received for publication July 22, 1974.

Contribution No. 394.

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