Effect of Ethephon on Coloration and Maturation of Wine Grapes

Abstract

'Zinfandel,' 'Grenache,' and 'Barbera' grapevines were sprayed with ethephon at 1,000 ppm when the surface of the berries was approximately 15 and 60% colored; 'Ruby Cabernet' was sprayed with the compound at 300 and 1,000 ppm at 3%, 20%, 60%, and 98% color. Some fruits of 'Zinfandel' and 'Ruby Cabernet' were enlarged by some treatments. 'Grenache' sprayed at 15% color developed a lower soluble solids content than did the controls, and some fruits of all cultivars except 'Barbera' had lower acid content than the controls. Ethephon applied to 'Ruby Cabernet' at 1,000 ppm on August 12, 19, or 26 stimulated anthocyanin production. Application to 'Zinfandel' on August 4 or 18 also increased color, whereas with 'Grenache' and 'Barbera' only the application on August 11 induced a significant increase in color. Application only to foliage enhanced anthocyanin formation, but application only to clusters was ineffective.