Southwest Michigan apple maturity report – September 18, 2024

Bill Shane, Michigan State University Extension -

Apple harvesting in southwest Michigan is moving rapidly.

Cross-sections of Red Delicious apples that have been stained blue with iodine.
The starch test for Red Delicious shows that this variety is generally mature in southwest Michigan. Photo by Bill Shane, MSU Extension.

This is our weekly southwest region apple maturity report. Reports are sent out following the Michigan State University Extension fruit team apple maturity calls on Wednesday morning. View Michigan State University Extension’s Apple Maturity page for regional reports throughout the state and additional resources.

Overview for this week

Commercial apple harvesting has focused on Red Delicious and Golden Delicious over the past week in central Berrien County. Honeycrisp harvesting is nearly done. Dry conditions have helped to speed picking by harvest crews. A very little internal watercore is showing up in some varieties. A new article by Michigan State University (MSU) researcher Randy Beaudry and others gives an in-depth look at the effects of climate change on apple ripening.

Commonly grown cultivars such as Red Delicious, Fuji, Honeycrisp, Jonagold, Granny Smith and Braeburn can have problems with watercore. Even some of our newer cultivars like Evercrisp (a Honeycrisp by Fuji cross) have susceptibility to watercore. Advanced maturity (ripe fruit) is a required feature for the development of watercore, so factors such as hot days plus cool nights that advance fruit maturity can promote watercore development.

Golden Delicious

This variety is averaging 5.1, a big jump over last week’s reading of 3.1 for the starch test; the mature starch threshold for fresh market is 3. The current average firmness reading is 17.1 lbs, about the same as last week; the desired minimum firmness for long-term controlled atmosphere (CA) storage is 17 lbs. This variety is ripening close to the predicted peak harvest date of Sept. 13 for central Berrien County. Picking Golden Delicious has been very active over the past week in most central Berrien County orchards.

Collection Date

Red Color (%)

Firmness (lbs)

Starch (1-8)

Soluble Solids (Brix)

Sep. 3

35.9 (20-30)

16.7 (15.8-18.2)

2.6 (1.6-3.2)

11.5 (10.7-12.3)

Sep. 9

30 (20-40)

16.7 (15.4-18.4)

3.1 (2.2-3.6)

12.2 (11.7-12.5)

Sep. 16

26 (15-40)

17.1 (15.5-19.3)

5.1 (4.4-6.2)

13.2 (11.9-15.7)

*Starch values according to the 1-8 scale developed by Cornell University.

Jonagold

This variety is averaging 5.5 for the starch test, well into the mature zone; the starch threshold for fresh market is 3.5. The current average firmness reading is 16.9 lbs, the desired minimum firmness for long-term CA storage is 17 lbs. The predicted peak harvest date for central Berrien County is Sept. 10. Most area Jonagold orchards have been picked. Some Jonagold fruit are showing poor blush development and some watercore this year due to the heat.

Collection Date

Red Color (%)

Firmness (lbs)

Starch (1-8)

Soluble Solids (Brix)

Sep. 3

62.6 (37.5-89)

19.4 (16.4-22)

2.6 (2-4)

12.3 (11.4-13.4)

Sep. 9

74 (50-96)

17.3 (16.2-20)

4.9 (3.4-6.6)

13 (12.1-15.6)

Sep. 16

68 (50-89)

16.9 (15.9-17.6)

5.5 (4.6-6.8)

14.1 (13.1-15.4)

*Starch values according to the 1-8 scale developed by Cornell University.

Red Delicious

This variety was sampled for the second time this week. This variety is averaging 3.3 for the starch test; the mature starch threshold for fresh market is 2.5. The current average firmness reading is 17.3 lbs; the desired minimum firmness for long-term CA storage is 18 lbs. This variety is maturing slightly ahead of the predicted peak harvest date of Sept. 17 for Red Delicious in central Berrien County. Picking has started or finished in about half of the Red Delicious orchards in central Berrien County.

Collection Date

Red Color (%)

Firmness (lbs)

Starch (1-8)

Soluble Solids (Brix)

Sep. 9

99 (96-100)

17.9 (17.3-19)

2.8 (2-3.2)

10.3 (9.7-11.1)

Sep. 16

98.3 (95-100)

17.3 (16-18)

3.3 (2.8-4.2)

11.3 (10.4-12.5)

*Starch values according to the 1-8 scale developed by Cornell University.

Fuji (main season)

This variety is averaging 3 for the starch test; the mature starch threshold for fresh market is 3. The current average firmness reading is 18.8 lbs; the desired minimum firmness for long-term CA storage is 18 lbs. The predicted peak harvest date for Central Berrien County is Sept. 13, which seems to be on target. Picking can be delayed waiting for better size, blush and brix. Picking has not started in Berrien County area Fuji orchards.

Collection Date

Red Color (%)

Firmness (lbs)

Starch (1-8)

Soluble Solids (Brix)

Sep. 9

51 (40-72)

19.1 (17.7-21.5)

2.8 (2-3)

11.5 (9.9-13.2)

Sep. 16

60.4 (40-82)

18.8 (17.3-21.6)

3 (2.2-3.8)

12.1 (11.3-14.1)

*Starch values according to the 1-8 scale developed by Cornell University.

IdaRed

This variety is averaging 2.7 for the starch test; the mature starch threshold is 3.5. The current average firmness reading is 16.3 lbs; the desired minimum firmness for long-term CA storage is 16 lbs. The predicted peak harvest date for central Berrien County is Sept. 24, which seems to be on target. Picking can be delayed a few days waiting for better size and brix. Some picking of IdaRed has started in Berrien County area orchards.

Collection Date

Red Color (%)

Firmness (lbs)

Starch (1-8)

Soluble Solids (Brix)

Sep. 16

71.1 (60-77.5)

16.3 (15.1-18.4)

2.7 (2-3.8)

11.6 (10.7-12.5)

*Starch values according to the 1-8 scale developed by Cornell University.

Rome

This variety is averaging 3 for the starch test; the mature starch threshold is 3. The current average firmness reading is 20.5 lbs; the desired minimum firmness for long-term CA storage is 18 lbs. The area Romes are slightly ahead of the predicted peak harvest date for central Berrien County of Sept. 24. Picking can be delayed waiting for better size and brix. Picking has not started in Berrien County area Rome orchards.

Collection Date

Red Color (%)

Firmness (lbs)

Starch (1-8)

Soluble Solids (Brix)

Sep. 16

69.6 (50-89)

20.5 (19.9-21.4)

3 (3-3)

12.1 (10.2-11.8)

*Starch values according to the 1-8 scale developed by Cornell University.

Evercrisp

This variety is averaging 1.9 for the starch test. The optimal starch value for long-term CA storage is 2.5, the mature threshold is 3. The current average firmness reading is 23.9 lbs, the desired firmness for long-term CA storage is 22 lbs. Picking can be delayed waiting for better size, blush and brix. Picking has not started in Berrien County area Evercrisp orchards. A few fruit are showing internal water core.

Collection Date

Red Color (%)

Firmness (lbs)

Starch (1-8)

Soluble Solids (Brix)

Sep. 16

66 (57.5-75)

23.9 (22.3-25.5)

1.9 (1-3)

13.2 (12.5-14.7)

*Starch values according to the 1-8 scale developed by Cornell University.

Apple maturity sampling parameters

  • Color % = the visual percentage of red color (blush) from 0 to 100; range shown is for the orchard averages.
  • Firmness in lbs pressure, skin off, as measured with a FT Penetrometer; range is for the site averages.
  • Starch: 1 = all starch (solid blue staining), 8 = no starch (white); range is for the site averages. Starch Iodine Index Chart.
  • Brix = % sugar measured with Atago PAL-1 Pocket Refractometer

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

Variety

Firmness (lbs)*

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

Braeburn

16

17

18

2.5

7

See the following helpful resources for more information:

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).

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