Submitted to: Hortechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/27/2002
Publication Date: N/A
Citation: Interpretive Summary: Red color is an important criterion for red skinned apples in the U.S. Obtaining a high level of red color is difficult for a number of apple cultivars grown in the mid-Atlantic region of the U.S. A series of studies were conducted over four years using a reflective metalized poly film placed on the orchard floor between the apple tree rows or under the canopy yto examine the effect on red color development. The reflective film improved apple color in several cultivars & on trees of several sizes. A high-density film was significantly cheaper than a low-density film with no difference in performance. The results of these studies provide new information for extension specialists & apple growers seeking methods to improve red color on apples.
Technical Abstract: Replicated studies from 1996 to 1999 were conducted to evaluate the effect of a metalized reflective film (RF) on red color development in several apple cultivars that often develop poor to marginal color in the mid-Atlan- tic 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 pre- -dicted maturity date. Light reflected into the canopy from the RF was measured & compared to a standard orchard sod, a killed sod, or various poly films. Fruit color was estimated visually & with a hand-held spectro- photometer. Fruit quality (firmness, soluble solids, starch index) was det- termined from a representative sample of fruit. A RF increased the level of photosynthetic photon flux (PPF) reflected into the canopy resulting in darker, redder colored 'Delicious','Empire', & 'Fuji' apples with a greater percent of surface showing red color. The RF increased canopy temperature & &fruit surface temperature. A white poly film increased reflected PPF & fruit color, but not to the extent of the metalized RF. Large (>4m h) well- pruned 'Delicious' trees showed increase fruit color especially when RF was placed under the canopy, but 'Empire' trees of similar size & a more dense canopy showed no effect. The effect of the RF was most pronounced in the lower portion(up to 2.5 m h) of the canopy. A high-density RF was as effec- tive as a low-density RF & the high-density film was about60% less expen- sive. A high-density RF may be a cost effective method to enhance red color on selected apple cultivars in the mid-Atlantic region. The RF & ethephon comparisons were variable: ethephon appeared to have more effect on color in 'Empire' than the RF, but less effect than RF on 'Hardibrite Delicious'. Ethephone consistently advanced fruit maturity.