2018 Apple Maturity Assessment: Week Four

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 un-ripe to tree-ripe and then begin to drop.
2018 Apple Maturity Assessment: Week Four - News

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Photo credit: Chris Walsh, University of Maryland

With the last ten days of 90°F heat, tree-ripening accelerated. Growers who have not already picked their Premier Honeycrisp might want to consider applying a pre-harvest drop spray.

Premier Honeycrisp

While some growers have completed Premier Honeycrisp harvest, many have not. Hot weather and abundant soil moisture increased fruit size by about 50% in the past week. Based on that change in fruit weight, spot-picked fruit size in the block we monitor changed from a 98 count box to a 66 count box.

Figure 1. Premier Honeycrisp apples spot-picked on August 7 (Left) and August 14 (Right) from the same orchard block in Adams County. One week of hot, rainy weather increased red color development, reduced chlorophyll, and caused a dramatic increase in fruit size. Photo credit: Kathy Hunt, University of Maryland

Gala and Honeycrisp

With the recent increases in Honeycrisp acreage, managing harvest in late-August can be difficult. Growers can find themselves moving harvest crews between peach and apple blocks. As Gala acreage increased, so did the use of the ethylene synthesis inhibitor AVG, the active ingredient in ReTain. This not only helped to spread out the Gala harvest but also delayed ripening and improved size and color picked in ReTain-treated blocks.

Gala is a relatively heat-tolerant apple but did not stand up well to the hot weather during the past two seasons. During the past 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 started monitoring Maryland grown, Retain-treated Gala and Honeycrisp fruit. Sampling was done in a Central Maryland orchard at about 575 feet elevation where fruit maturity should be similar to Pennsylvania orchards along the Mason Dixon Line. This location should provide data before most growers reading this newsletter begin picking those two varieties.

While these observations were taken from fruit grown on slender-spindle trees, be sure to check your fruit maturity. Small differences in microclimate or orchard management may make a large difference in maturation and tree ripening. Two management practices that can hasten fruit maturity are (1) summer PGR applications to enhance return bloom and (2) mechanical pruning to increase red color development.

The following table shows data from our pre-harvest samples taken in a Central Maryland block during the past week. Based on this first sample, harvest in this block is likely to begin “on time” during the third week of August.

CultivarDiameter (inches)Red Color (%)Ground ColorFirmness (pounds)Starch Pattern (1 – 8)Soluble Solids (°Brix)

Honeycrisp

10-Aug-18

33Light green20.61.411.3

Gala

10-Aug-18

2.712.5Yellowish green19.9211

Figure 2. Fruit color and starch staining pattern of Gala apples (Upper row) and Honeycrisp apples (Lower row) spot-picked in a commercial orchard in Central Maryland during early August. Photo credit: Kathy Hunt, University of Maryland

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