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Grand Rapids area apple maturity report – Aug. 10, 2021 - Apples

Grand Rapids area apple maturity report – Aug. 10, 2021

This is the first apple maturity report for the 2021 harvest season.

Honeycrisp apples treated for the Starch-Iodine test.
Honeycrisp apples treated for the Starch-Iodine test. Fruits are very immature with no starch clearing present as of Aug. 8, 2021. Photo by Amy Irish-Brown, MSU Extension.

Welcome to the first Grand Rapids, Michigan, area apple maturity report for the 2021 harvest season! Reports will be sent out every week (usually on Wednesdays) following the Michigan State University Extension fruit team apple maturity calls on Wednesday morning.

General information

As you know, many changes in apple physiology occur over time as fruit become more mature. Starch is converted to sugar, seeds turn a darker color, acidity decreases, chlorophyll levels decrease, respiration increases, cell walls weaken, fruit begins to soften and ethylene production increases. Our MSU Ridge Apple Quality Lab and the MSU campus Beaudry Lab measure these and many other factors to help you make harvest management decisions. We are graciously funded by the Michigan Tree Fruit Commission, Michigan Apple Committee, Michigan State Horticultural Society and Michigan State University Extension. Many thanks to all the growers and industry representatives that donate to our program.

To generate the data in this report, samples of approximately 10-20 fruit are collected from orchards across the Grand Rapids area on Monday and processed for maturity indicators on Tuesday mornings. These data and recommendations attempt to reflect regional averages, but maturity and condition of individual blocks will vary.

Updates for this week

  • Weather: The remainder of August is expected to be warmer and drier than normal. This will have an impact on drop-susceptible fruit and stop-drop materials. We will need a few cooler nights for better color development and a little more precipitation (or continued irrigation) to help with fruit size.
  • Pristine and Jersey Macs: These very early varieties including have begun picking!
  • Zestar and Ginger gold: These early varieties are approaching harvest in a week or two. Maturity metrics (starch, firmness, soluble solids) are indicating that are beginning to ripen. In these varieties, look for a change in background color from green to green/yellow and development of varietal flavor.
  • Predicted harvest dates according to the Maturity Model in Enviroweather are about 10 days earlier than normal for early varieties (Gala, Honeycrisp, McIntosh), making this week about 21 days before harvest for Honeycrisp and Gala. At this time, we believe this will be fairly accurate.
  • Mixed maturity is evident in most varieties and locations. Multiple picks may be needed to harvest fruit at the appropriate maturity for successful storage conditions.
  • Some frost damage is evident in locations in the form of russeting, frost rings and misshapen fruit.

Paula Red

Paula’s are approaching maturity quickly. Already, fruit has very good size and color in most locations. Varietal flavor is also apparent, although fruit is still somewhat starchy. Some very mild water core was observed in a few fruit. Seeds are beginning to turn brown.

The main indicators for this variety are changing of the background color from green (5) to a cream/yellow color (3-4), starch approximately 3.0, and firmness between 15-16 lbs. Stems will also loosen on the tree.

Variety

Location

Fruit Weight (g)

Ethylene (% >0.2ppm)

Red color (%)

Background color

Firmness (lbs)

Starch

Soluble solids (°Brix)

Notes

Paula Red

Belding1

180

na

68.5

5.0

16.7

2.4

12.4

seeds 25% brown, mild watercore

Paula Red

Belding2

175

na

66.5

5.0

15.4

2.9

11.1

seeds 25% brown, mild watercore

Average

 

178

na

67.5

5.0

16.1

2.7

11.8

 

Max

 

180

na

68.5

5.0

16.7

2.9

12.4

 

Min

 

175

na

66.5

5.0

15.4

2.4

11.1

 

Recommended

 

 

 

90.0

4.0

15-16

3.0

 

 

Ruby Mac

There are some signs of fruit beginning to mature. It will likely be a couple more weeks until earlier McIntosh strains will begin harvest. Very nice color development on most fruit, but still very firm, low sugars (soluble solids/Brix). Some starch clearing has started.

Variety

Location

Fruit Weight (g)

Ethylene (% >0.2ppm)

Red Color (%)

Background color

Firmness (lbs)

Starch

Soluble Solids (°Brix)

Ruby Mac

Ridge3

110

na

76.5

5.0

18.3

2.2

10.5

Ruby Mac

Ridge4

120

na

84.0

5.0

17.9

2.0

9.9

Ruby Mac

Ridge5

115

na

75.5

5.0

18.9

2.4

10.2

Average

 

115

na

78.7

5.0

18.4

2.2

10.2

Max

 

120

na

84.0

5.0

18.9

2.4

10.5

Min

 

110

na

75.5

5.0

17.9

2.0

9.9

Recommended

 

 

 

 

 

14-16

5-7

 

Honeycrisp

Not close yet. All fruit that were tested were very starchy, low in sugar content and had high firmness. Minimal color development was observed in almost all locations—only a handful of fruit have begun to start some red color development and background color is still very green. Some fruit is already very large in size, although highly dependent on crop load, which is considerably variable this season.

It will be tempting to pick this variety early this season due to the somewhat light crop. But it is important to harvest at optimal maturity to achieve good quality and minimize storage disorders.

The most recent Honeycrisp virtual meetup was on the topic of harvest and postharvest management of Honeycrisp with Randy Beaudry, Chris Watkins and others. Watch the Virtual Honeycrisp Meetup recording here.

Variety

Location

Fruit Weight (g)

Ethylene (% >0.2ppm)

Red Color (%)

Background color

Firmnes (lbs)

Starch

Soluble Solids (°Brix)

Standard

Belding1

150

na

0.5

4.6

22.1

1.0

9.0

Standard

Belding2

180

na

2.0

5.0

20.2

1.0

9.7

Standard

Belding3

160

na

3.0

5.0

22.4

1.0

10.3

Standard

Ridge2

140

na

6.0

4.8

21.7

1.0

11.3

Standard

Ridge3

150

na

5.5

4.5

22.1

1.0

10.7

Standard

Ridge4

160

na

0.0

5.0

21.0

1.0

9.4

Standard

Ridge5

140

na

4.5

4.6

20.8

1.0

11.5

Standard

Standale1

180

na

2.0

5.0

20.1

1.0

10.4

Standard

Standale2

220

na

1.5

5.0

20.4

1.0

10.7

Average

 

164

na

2.8

4.8

21.2

1.0

10.3

Max

 

220

na

6.0

5.0

22.4

1.0

11.5

Min

 

140

na

0.0

4.5

20.1

1.0

9.0

Recommended

 

 

 

 

 

15-17

3.5-7

 

Gala

Not close yet. All fruit that were tested were very starchy, low in sugar content, and had high firmness. Color development varies considerably by location and strain. Red color was well developed in some locations, but background color remains very green in all places. A high coloring strain does not necessarily indicate earlier maturity, so it is important to pay attention to other maturity indicators. There is a very good crop in most locations, size is still small but will improve quickly over the coming weeks.

Early strains (e.g. ‘Wildfire’) maturing approximately two weeks ahead of standard strains. Picking will likely begin in a week or two.

Variety

Location

Fruit Weight (g)

Ethylene (% >0.2ppm)

Red Color (%)

Background color

Firmness (lbs)

Starch 

Soluble Solids (°Brix)

Brookfield

Belding1

130

na

3.5

4.8

24.2

1.0

9.7

Galaxy

Belding2

130

na

7.0

5.0

24.0

1.0

9.9

Buckeye

Belding2

110

na

12.5

4.4

22.2

1.0

8.9

Brookfield

Belding3

120

na

9.0

4.6

27.4

1.0

9.4

Brookfield

Ridge2

110

na

18.5

4.7

24.0

1.0

11.1

Brookfield

Ridge3

130

na

7.5

4.5

27.9

1.0

9.6

Brookfield

Ridge4

130

na

5.0

5.0

21.4

1.0

8.8

Brookfield

Ridge5

110

na

5.5

4.8

23.7

1.0

9.2

Brookfield

Standale1

130

na

5.0

4.8

26.7

1.0

10.9

Brookfield

Standale2

120

na

6.0

4.7

25.7

1.0

10.0

 

 

 

 

 

 

 

 

 

Average

 

122

na

8.0

4.7

24.7

1.0

9.8

Max

 

130

na

18.5

5.0

27.9

1.0

11.1

Min

 

110

na

3.5

4.4

21.4

1.0

8.8

Recommended

 

 

 

 

 

16-18

3-6

 

Apple maturity sampling parameters

  • % fruits with internal ethylene over 0.2 ppm = indicates when ethylene begins to influence fruit ripening and it cannot be held back easily after this is reached.
  • Color % = the visual percentage of red color from 0 to 100; range is of all fruits tested
  • Background color: 5 = Green, 1 = Yellow; range is of all fruits tested.
  • Firmness in pounds pressure = measured with a Güss Fruit Texture Analyzer; range is of all fruits tested.
  • Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.
  • Brix = % sugar measured with Atago PAL-1 Pocket Refractometer

Looking for more? View Michigan State University Extension’s Apple Maturity page for regional reports throughout the state and additional resources.

Suggested firmness and starch index levels for long-term and shorter-term controlled atmosphere (CA) storage by variety.

Variety

Firmness (pounds)*

Starch Index*

Short CA

Mid-CA

Long CA

Mature

Over mature

McIntosh

14

15

16

5

7

Gala

16

17

18

3

6

Honeycrisp

15

16

17

3.5

7

Empire

14

15

16

3.5

6

Early Fuji

16

17

18

3

7

Jonagold

15

16

17

3.5

5.5

Jonathan

14

15

16

3.5

5.5

Golden Delicious

15

16

17

3

6.5

Red Delicious

16

17

18

2.5

6

Idared

14

15

16

3.5

6

Fuji

16

17

18

3

7

Rome

15

16

18

3

5.5

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