Ethephon has mixed effects on table grapes
The growth regulator ethephon (Ethrel) has been shown to improve coloring of the table grape varieties, Red Malaga, Queen, Tokay, and Emperor if applied after some of the berries have begun to show color. Preliminary trials with Cardinals showed slight color benefits, of dubious commercial significance. Trials with Ribier have never shown benefit. More detailed trials were established at the Kearney Horticultural Field Station near Parlier in Fresno County during the 1976 season.