Summary of Apple Fruit Maturity During August and September 2018

This year’s bloom was later than in 2017. With a later bloom and a cool rainy season, we initially wondered when this year’s apple crop would be ready to pick.
Summary of Apple Fruit Maturity During August and September 2018 - News

Updated: October 9, 2018

Summary of Apple Fruit Maturity During August and September 2018

Rainy weather had given everyone headaches with plant diseases and red color development. Until August, the cool, rainy weather was a concern. Then things changed, and August and September weather was warmer than average.

While we haven’t had many record heat days this summer, August temperatures were still above average. High humidity trapped heat at ground level, frequently keeping night temperatures above 70°F. This is the same principle that reduces frost on cloudy spring nights, while clear spring nights allow orchard temperatures to drop. Warm summer nights also increase fruit respiration, and in doing so decrease fruit sugar. Unfortunately, the first few days in October are continuing this warm pattern. The difficulty in handling large, poorly colored fruit will continue until temperatures return to normal.

Premier Honeycrisp

Rapid maturation and tree ripening are the hallmarks of early-season apples. During the past few years, this has been particularly problematic with varieties that tree-ripen in August. Honeycrisp and Jonagold were selected by fruit breeders working in cool growing areas. Having been chosen for cool climates, they are particularly prone to rapid ripening and pre-harvest drop when grown in the warmer Mid-Atlantic region.

We have been monitoring Premier Honeycrisp maturation and tree ripening for the past three years. Every year we are surprised how quickly they move from unripe to tree-ripe and then begin to drop. With ten days of 90° heat, tree-ripening accelerated.

The following table shows data from our pre-harvest samples taken in the same orchard block at the beginning of harvest season. As you can see, harvest maturity data changed dramatically between July 31 and August 7.

Table 1. Premier Honeycrisp Harvest Maturity Data

DateDiameter (inches)Red Color (%)Ground ColorFirmness (pounds)Starch Pattern (1 – 8)Soluble Solids (°Brix)
25-Jul-182.89Light Green18.91.410.9
31-Jul-182.919Yellowish Green16.42.810.9
7-Aug-183.135Greenish Yellow13.96.212.1

We noticed hot weather and abundant soil moisture increased fruit size about 50 % during maturation. Based on that change in fruit weight, spot-picked fruit size in the block we monitored changed from a 98 count box to a 66 count box. This rapid increase in fruit size can be attributed to abundant rainfall coupled with a loss of starch, increasing soluble solids, and the fruit’s osmotic potential.

Gala

While we have had a few August apples for centuries, the increase in August harvests began with Paulared, but then dramatically increased with Gala and Ginger Gold. While Gala was a small apple, its flavor and greater heat tolerance made it a hit in Appalachian orchards. In Maryland, we've usually picked the original Galas (or Kidd’s D-8) about the same time as Loring peaches - between August 15th and August 25th.

Gala is a relatively heat-tolerant apple, but it did not respond well to the hot weather during the past two seasons. During the last two years. Gala maturity quickly went from immature to overripe. While this was going on, Honeycrisp was maturing too, leading to a picking and marketing dilemma.

In this year's maturity trials, we sampled ReTain-treated Gala fruit in Central Maryland grown at 575 feet elevation, which should be similar to maturity in southern Pennsylvania. Gala maturity changed markedly during the maturation process. Tree-ripe fruit with an orange-red color reminiscent of Cox’s Orange Pippin were nearly devoid of starch and had softened to 14.6 pounds firmness by August 28.

Once Galas are tree-ripe, they lose shelf life and become susceptible to rain cracking. As fruit starch is broken down into sugar, the osmotic potential of the fruit increases. That change in soluble solids pulls water into the fruit, causing fault areas in the stem end to crack. While fruit size was good and we did not see fruit loss to large cracks, about 10 % of the fruit we sampled had ½ inch-long stem-end cracks.

Honeycrisp

Fruit size was good in Honeycrisp, but high temperatures accelerated ripening, causing fruits to soften and lose starch rapidly. In early-September, firmness averaged 13 - 14 pounds which was 2.3 pounds less than the previous week. Averages did not tell the complete story, however. At that time the fruit we tested ranged from 16 pounds to 10 pounds firmness. Clearly, the data from that small sampling show the potential variability of storage life and shelf life caused by the hot summer weather. (Table 2) While Honeycrisp fruit size was excellent, red color development was retarded by August temperature.

We noticed an apparent ‘final swell’ that accompanied the loss in starch similar to that observed in Premier Honeycrisp. Fruit weight increased dramatically in the last week of sampling, from 195 grams to 233 grams, which was an increase of 3 % a day.

As growers wait for red color development, continued fruit growth is also leading to other physiological problems. Despite spot-picking, we noticed problems with stem-end russetting and bitter pit. What was not expected was the significant percentage of fruit with shoulder-cracks and the small percentage of soft apples with internal breakdown. (Photo 2)

Table 2. The following table shows data from our apple samples evaluated during the period of Honeycrisp maturation and tree-ripening.

Honeycrisp – Adams County Pennsylvania 1200 feet elevation

DateDiameter (inches)Red Color (%)Ground ColorFirmness (pounds)Starch Pattern (1 – 8)Soluble Solids (°Brix)
14-Aug-183.018Light green18.21.210.5
21-Aug-183.040Yellowish green17.32.811.4
28-Aug-183.229Yellowish green16.13.612.0
4-Sep-183.439Light yellow14.46.112.7
11-Sep-183.445Light yellow13.06.913.1
18-Sep-18Harvest Complete

In addition to blemishes at harvest shown in Photo 2, we also see blemished fruit in Washington, DC area supermarkets (Photo 3). Since pitting increases in storage and transit, we assume the fruit shown in this photo were blemish-free when packed but continued to pit between the packing house and the supermarket.

A cool, wet growing season led to soggy breakdown. While this season started cool and wet, the August heat wave may have stressed the fruit. Taken together, Honeycrisp maturation appeared to be “on time” with many growers picking this crop just after Labor Day weekend.

Autumn Crisp

This year we added Autumn Crisp to our evaluations. On September 7 Autumn Crisp apples grown in central Maryland were tree-ripe. At that time they were 3.3” in diameter with 65 % red color. They had softened to 13.3 pounds with virtually no starch left in the flesh. Their flavor was good, and they had soluble solids measuring over 15 Brix.

Daybreak Fuji

The hot, wet summer weather affected Daybreak Fuji much more than Autumn Crisp. While size was not a problem, red color development was. Daybreak Fuji had less than 50 % pale red color at harvest. Larger Daybreak fruit lacking starch are prone to stem-end cracks, which were reminiscent of over-mature Gala. In the samples we studied, about 10 percent of the spot-picked Daybreak Fuji had some cracking.

Daybreak Fuji had almost no starch in the flesh and tasted tree ripe in samples picked on September 19 and 25. Since spot-picking had begun in this block, fruit maturity in both varieties remained relatively constant in mid-September. The Daybreak block sampled was picked out shortly after the September 25 sampling date.

CrimsonCrisp

The red-color in this variety was impressive in 2018. While this is a smaller apple than Autumn Crisp and Daybreak Fuji, it had a deep red color. Some fruit were blemish-free while others had shown considerable roughness, primarily on the stem end. CrimsonCrisp fruit were still quite firm in late September. The starch pattern index for CrimsonCrisp was about one week behind Daybreak Fuji on all three September sampling dates.

Photo 1. Apple fruit size and color development in early September 2018 in Central Maryland. Daybreak Fuji (upper row), Autumn Crisp (middle row), and CrimsonCrisp (bottom row). Despite the hot, humid weather, Autumn Crisp and CrimsonCrisp developed excellent red color. Photo: Kathy Hunt, University of Maryland

Photo 2. Honeycrisp apples are prone to a number of physiological disorders. Left apple – bitter pit; Center apples – shoulder cracking and stem-end russet; Right apple – onset of internal browning. Photo: Kathy Hunt, University of Maryland

Photo 3. Honeycrisp apples on display in a Washington, DC area supermarket. The pitting seen on many of the fruits probably developed after they were packed and shipped. Photo: Kathy Hunt, University of Maryland

Authors

Tree Fruit Cultural Practices and Production Systems Sustainable Specialty Crop Production Support for Next Generation Farmers from Diverse Backgrounds

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Christopher S. Walsh