The Use of Reflective Film and Ethephon to Improve Red Skin Color of Apples in the Mid-Atlantic Region of the United States

Abstract

Replicated studies were conducted from 1996 to 1999 to evaluate the effect of a metalized reflective film (RF) on red color development in several apple (Malus ×domestica) cultivars that often develop poor to marginal color in the mid-Atlantic growing region. Film was applied to the orchard floor in the middle between tree rows or under the tree beginning 5 to 7 weeks before the predicted maturity date. Light reflected into the canopy from the RF was measured and compared with a standard orchard sod, a killed sod or various polyethylene films. Fruit color was estimated visually and with a hand-held spectrophotometer. Fruit quality (firmness, soluble solids, starch index) was determined from a representative sample of fruit. RF increased the level of photosynthetic photon flux (PPF) reflected into the canopy resulting in darker, redder colored `Delicious', `Empire', and `Fuji' apples with a greater proportion of surface showing red color. RF increased canopy temperature and fruit surface temperature. A white polyethylene film increased reflected PPF and fruit color, but generally not to the extent of the metalized RF. Large [>13 ft (4.0 m) height] well-pruned `Delicious' trees showed increased fruit color, especially when the RF was placed under the canopy, but `Empire' trees of similar size and a more dense canopy showed no effect. The effect of the RF was most pronounced in the lower portion [up to 8 ft (2.4 m) height] of the canopy. A high-density RF was as effective as a low-density RF and the high-density film was about 60% less expensive. A high-density RF may be a cost effective method to enhance red color on selected apple cultivars in the mid-Atlantic region. Comparisons between ethephon and the RF were variable: ethephon appeared to have more effect on color in `Empire' than the RF, but less effect than the RF on `Hardibrite Delicious'. Ethephon consistently advanced fruit maturity. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).