2016 Apple Maturity Assessments—Week 5
Posted: September 2, 2016
This fruit is grown at a warm, low-elevation site (520 feet) in southern Washington County, MD. Trees used in this study are planted on size-controlling Geneva rootstocks, and trained to the tall-spindle system. The information is then distributed through the Penn State Extension network to growers as a collaboration of the Mid-Atlantic Fruit Consortium.
Brookfield Gala apples grown at Keedysville, MD matured and ripened quite quickly this year. Good light exposure provided by the tall-spindle system, coupled with the relentless string of 90 degree days in August, compressed early apple harvests. Brookfield Gala harvest at Keedysville ended on August 26th, which was only a week after spot-picking began.
As Gala fruit size increases, its cracking potential also increases. If any significant rainfall occurs before Gala harvest ends, tree-ripe fruit is susceptible to cracking. This is always a problem with this variety, but particularly problematic in years like 2016 when size and red color are slow to develop.
Treating trees with AVG (ReTain) to suppress ethylene synthesis and fruit ripening temporarily reduces the cracking risk. AVG will not prevent cracking, however, if harvest is delayed too long.
Red color increased and fruit firmness decreased in Honeycrisp apples at Keedysville during the past week. While red color is slow to develop, fruits are losing their ground color. The photo below shows the current range of ground color in Honeycrisp.
Honeycrisp ground color of fruit picked this week from tall-spindle trees at Keedsyville, MD. Ground color of the fruit ranged from Light Green (left), Yellowish Green (second from left), Greenish Yellow (middle), Light Yellow (second from right) and Whitish Yellow (right). Photo: C.S. Walsh
While apples always look redder on the tree than in the bin, this was particularly true with these Honeycrisp. The failure of chemical thinning treatments left doubles and triples on the tree. Those poorly-thinned fruit had less than 50 % red color.
In addition to lack of red color, many of the harvested Honeycrisp apples at Keedysville had a rough finish. This roughness was likely caused by cool, wet spring weather conditions. The hot, dry summer weather also affected fruit finish, with lenticel breakdown in some smaller fruit grown in full sun.
CrimsonCrisp (Co-op 39)
CrimsonCrisp fruit picked at Keedysville were smaller, firmer, and redder, with slightly greater soluble solids (sugar levels) than the Honeycrisp at this site. The CrimsonCrisp fruit were quite firm, with median firmness of 23.4 pounds. Some fruit were so firm that they were tough to bite into.
While the fruit were still not quite ready to harvest, we were surprised to see more than ten percent of these apples had watercore. In some fruits this symptom was restricted to the core region, while in others the glassy area surrounded the vascular bundles. Watercore is thought to occur when sorbitol is translocated from the leaves to the fruit, but does not move inside the cells of the fruit flesh. This sorbitol concentration attracts water to the intercellular spaces outside the flesh cells. Normally watercore is seen in late-season apples that mature in cool weather. Seeing it in an early-September apple is unexpected.
More details on maturity, including firmness, fruit size, soluble solids and red color, are posted at Apple Maturity Assessments.
This project is supported by the State Horticultural Association of Pennsylvania Research Committee and is a cooperative effort of University of Maryland Extension and Penn State Extension.