2018 Apple Maturity Assessment: Week Six

While Gala is a small apple, its flavor and heat tolerance has made it a mainstay of the August harvest.
2018 Apple Maturity Assessment: Week Six - News

Updated: September 6, 2018

2018 Apple Maturity Assessment: Week Six

Figure 1. Tree-ripe Gala (Kidd’s D-8) apple picked in Central Maryland on August 29, 2018. This apple had a visible stem-end crack, with little starch (blue stain) in the flesh. Photo credit: Kathy Hunt, University of Maryland

When the variety was first marketed in New Zealand, growers picked export-grade fruit when the ground color had turned “white” which occurs in mid-August in Maryland. Like any early apple, Gala fruit can quickly move from immature to overripe, especially in hot weather.

In this year's maturity trials, we sampled ReTain-treated Gala fruit in Central Maryland grown at 575 feet elevation. Fruit maturity there should be similar to maturity in southern Pennsylvania. As you see in Table 1, Gala maturity changed markedly during the past two weeks. Tree-ripe fruit with an orange-red color reminiscent of Cox’s Orange Pippin was nearly devoid of starch and had softened to 14.6 pounds firmness. Shipping mature Gala apples that had received a full rate of ReTain still retained some starch and were firmer (Table 1).

Once Galas are tree-ripe, they lose shelf life and are 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 (Figure 1).

During the past decade, most growers have moved away from the original Gala to new cultivars with greater red color like Regal, Royal, Buckeye and Ultima Gala. This change allows growers to pick earlier, reduce rain cracking, and have better packouts.

Table 1. Pre-harvest Gala apple samples evaluated in August

Gala: Central Maryland 575 feet elevation

DateReTain TreatmentDiameter (inches)Red Color (%)Ground ColorFirmness (pounds)Starch Pattern (1 – 8)Soluble Solids (°Brix)
10-Aug-182.712.5

Yellowish-green

19.9211
21-Aug-18ReTain (1x)327Whitish-yellow14.95.611.6
21-Aug-18ReTain (2x)2.920Whitish-yellow16.24.411.1
28-Aug-18ReTain (1x)2.940Whitish-yellow14.67.612.5
28-Aug-18ReTain (2x)2.825Light yellow16.45.513.6

Honeycrisp

Two recent heat waves decreased red color development in sampled fruit (Table 2). These apples also decreased in firmness and ground color but increased in fruit size (Table 2). With our recent hot weather, spot picking on the size and red color is particularly important. Penn State Extension published a nice calculator that determines potential economic returns on the value of spot picking .

This grower-supported project also tested the effects of pre-conditioning on storage of Premier Honeycrisp and Honeycrisp apples. Preconditioning is a widely-used practice by northern apple growers to avoid “chilling injury” in storage. This is not a common practice for mid-Atlantic growers, and we did not see typical chilling injury symptoms in our 2016 and 2017 storage trials. Those were both hot, dry summers which may explain the lack of chilling injury. A cool, wet season of 2014 led to storage losses from soggy breakdown. Since chilling injury tends to be associated with cool, wet weather early in the season, 2018 may be a year where preconditioning could reduce chilling injuries. Unfortunately, we do not have adequate data to make that a pre-storage recommendation.

While these observations were taken from fruit grown on slender-spindle trees, check your fruit maturity as small differences in microclimate or orchard management may make a large difference in maturation and tree ripening. Management practices that might hasten fruit maturity are summer PGR applications to enhance return bloom, mechanical pruning to increase red color development and the planting of new red-colored varieties.

Table 2. Pre-harvest Honeycrisp apple samples evaluated in August

Honeycrisp: Central Maryland 575 feet elevation

DateReTain TreatmentDiameter (inches)Red Color (%)Ground ColorFirmness (pounds)Starch Pattern (1 – 8)Soluble Solids (°Brix)
10-Aug-1833Light green20.61.411.3
21-Aug-18No ReTain350Yellowish-green16.36.811.5
21-Aug-18ReTain2.920Yellowish-green16.34.710.6
28-Aug-18No ReTain3.245Yellowish-green16.37.513.9
28-Aug-18ReTain3.120Light green185.711.5

Honeycrisp: Adams County PA 1200 feet elevation

DateDiameter (inches)Red Color (%)Ground ColorFirmness (pounds)Starch Pattern (1 – 8)Soluble Solids (°Brix)
14-Aug-18318Light green18.21.210.5
21-Aug-18340Yellowish-green17.32.811.4
28-Aug-183.229Yellowish-green16.13.612

Figure 2. Gala (Kidd’s D-8) apples spot picked in Central Maryland on August 28, 2018. The orange-red colored fruit shown in three columns on the left received a half-rate of ReTain. The greener fruit in three columns on the right was treated with two half-rate sprays. Photo credit: Chris Walsh, University of Maryland

Figure 3. Honeycrisp apples spot picked in Central Maryland on August 28, 2018. The redder fruit shown in three columns on the left received no ReTain treatment (control). The greener fruit in three columns on the right was treated with ReTain. Photo credit: Chris Walsh, University of Maryland

Authors

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

More by Tara Baugher 

Christopher S. Walsh