DA readings refer to the level of chlorophyll (green color) in the fruit, just below the skin. As the fruit ripens, chlorophyll levels decline, and so do DA readings. Starch index, fruit firmness, and, to some degree, Brix values are commonly used to determine the level of fruit maturity and harvest date for most commercial apple varieties. Generally speaking, fruits intended for CA should be picked at starch index (3-5), firmness (> 16 lb), and DA reading (around 0.60). Apples intended for fresh consumption should be harvested at starch index (5.5-7), firmness (13-16 lb), DA reading (0.35), and Brix (12-14%).
Sherif M. Sherif, Assistant Professor of Horticulture at Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center 595 Laurel Grove Road, Winchester, VA 22602 Tel. 540-232-6035, Email: ssherif@vt.edu
