Southwest Michigan apple maturity report – Sept. 15, 2021

This is the third weekly apple maturity report for the southwest Michigan region.

Brown spotting and wilting on Honeycrisp apple leaves.
Zonal chlorosis of Honeycrisp leaves, a physiological disorder generally not thought to affect yield. Photo by Thomas Sanger.

This apple maturity report for the southwest Michigan region is sent out every week (usually on Wednesdays) following the Michigan State University Extension fruit team apple maturity calls on Wednesday morning.

Highlights for this week

Honeycrisp have become the focus of harvesting in the southwest region. Bitter rot is continuing to be a significant problem in some Honeycrisp blocks. Some sites are showing lenticel rot—small, discolored areas of rot with a lenticel in the center.

Some small oriental fruit moth larvae are showing up in unprotected fruit of various varieties. These larvae are the result of a moth flight in late August. Entry holes tend to be less conspicuous for this insect, often at the stem or calyx end of the apple. Codling moth entry holes tend to be in the side of the fruit.

Detailed information by variety

Mac and Gala

No more reports for these two varieties as they have reached full maturity.

Honeycrisp

Standard Honeycrisp starch conversion is averaging 5.8 from last week’s 3.1, with all five sites tested exceeding the 3.5 mature threshold. We are using the Cornell 1-8 scale for starch conversion for Honeycrisp in this report. Flesh firmness dropped another pound to an average of 15.3, approaching the level more suitable for shorter term controlled atmosphere (CA) storage. Brix levels improved significantly since last week.

Zonal chlorosis on leaves has resulted in leaf tattering, which tends to be worse in blocks with light crop and significant vigor. Bitter rot disease continues to spread in the three sites where it showed up several weeks ago. This fungal disease is favored by warm wet conditions and rotting nubbin fruit that did not fall from the tree during June drop. Bitter pit is present in some sites on a few fruit.

Standard Honeycrisp – Sampled Sept. 13, 2021

Site

Firmness (lbs)

Red color range (%)

Starch (1-7)

Soluble Solids (°Brix)

1

14.3

50 – 70

4.6

12.9

2

16.0

50 – 75

6.0

13.6

3

15.0

50 – 75

7.0

13.3

4

15.3

10 – 90

4.6

13.8

5

16.0

40 – 80

6.6

13.4

6

 

 

 

 

Average

15.3

 

5.8

13.4

Max

16.0

 

7.0

13.8

Min

14.3

 

4.6

12.9

Recommended

15-17

 

3.5-7

 

 

Honeycrisp maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Aug. 31

17.8 (17.0-19.0)

1.4 (1.0-2.0)

11.2

Sept. 7

16.8 (15.0-18.0)

3.1 (1.4-4.6)

12.0

Sept. 13

15.3 (14.3 – 16.0)

5.8 (4.6-7.0)

13.4

Jonagold

Jonagold were sampled for the second week. Starch indices average 3.2, approaching the threshold of 3.5 for this variety. Fruit firmness at 19.5, well above the threshold of 17 pounds, indicating harvesting can be delayed, waiting for better color. The predicted harvest date is Sept. 25 for central Berrien County. Some area Jonagold have been harvested for processing.

Jonagold – Sampled Sept. 13, 2021

Site

Firmness (lbs)

Red color range (%)

Starch

Soluble Solids (°Brix)

1

16.2

40-75

4.4

12.1

2

23.0

50-90

2.2

14.7

3

19.3

40-70

3

13.7

4

17.0

30-60

4.6

13

5

22.0

60-85

2

14.3

Average

19.5

 

3.2

13.6

Max

23.0

 

4.6

14.7

Min

16.2

 

2.0

12.1

Recommended

17-15

 

3.5

 

 

Jonagold maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 7

20.7 (18.2-23.3)

2.2 (1.2-3.0)

12.6

Sept. 13

19.5 (16.2-23.0)

3.2 (2.0-4.6)

13.6

Jonathan

This variety was sampled for the second week and the starch conversion is testing at an average of 3.4, about the same as last week, essentially at the 3.5 minimum threshold indicating fruit are internally mature. Firmness dropped 2 pounds to 17.0 and is still above the threshold of 16 pounds where fruit transition from suitable for long term CA to more suited for short term storage. Some Jonathan have been harvested for taffy apples.

Jonathan – Sampled Sept. 13, 2021

Site

Firmness (lbs)

Red color range (%)

Starch

Soluble Solids (°Brix)

1

17.2

60-98

4.0

12.5

2

19.2

50-58

3.0

12.6

3

17.1

70-90

3.0

12.2

4

18.0

30-60

3.6

13.0

Average

17.9

 

3.4

12.6

Max

19.2

 

4.0

13.0

Min

17.1

 

3.0

12.2

Recommended

16-14

 

3.5

 

 

Jonathan maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 7

20.0 (19.0-21.0)

3.3 (3.0-3.8)

12.2

Sept. 13

17.9 (17.1-19.2)

3.4 (3.0-4.0)

12.6

Empire

This variety was sampled for the second week. Firmness dropped about 2 pounds since last week but is still excellent at an average of 17.5 pounds. Starch conversion has reached 3.4, close to the 3.5 considered to be the threshold for internally mature. Brix is about the same as last week. Some Empire have been harvested for taffy apples but in general harvesting can be delayed. The predicted harvest date for central Berrien County is Sept. 21.

Empire – Sampled Sept. 13, 2021

Site

Firmness (lbs)

Red color range (%)

Starch

Soluble Solids (°Brix)

1

16.0

50-95

3.4

10.2

2

16.2

50-70

4.2

10.0

3

20.0

70-98

3.0

12.2

4

18.1

50-90

3.0

11.6

5

17.4

98-100

3.6

12.0

Average

17.5

 

3.4

11.2

Max

20.0

 

4.2

12.0

Min

16.2

 

3.0

10.0

Recommended

16-14

 

3.5

 

 

Empire maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 7

19.4 (17.4-22.1)

2.9 (2.0-4.0)

11.2

Sept. 13

17.5 (16.2-20.0)

3.4 (3.0-4.2)

11.2

Golden Delicious

This variety was sampled for the first time and has a predicted harvest date of Sept. 28 for central Berrien County. Firmness is testing an average of 17.6, close to 17, the lower range considered ideal for long term CA storage. Starch conversion tested 2.9, close to the 3.0 considered to be point where fruit become internally mature. This variety appears to be ahead of the predicted harvest date.

Golden Delicious – Sampled Sept. 13, 2021

Site

Firmness (lbs)

Red color range (%)

Starch

Soluble Solids (°Brix)

1

16.0

0

4.0

11.7

2

18.0

5-10

2.0

12.4

3

20.0

10-30

1.0

13.7

4

16.2

0

4.0

10.0

5

16.2

0

4.2

11.7

6

19.4

5-25

2.0

12.7

Average

17.6

 

2.9

12.0

Max

20.0

 

4.2

13.7

Min

16.0

 

1.0

10.0

Recommended

17-15

 

3.0

 

Red Delicious

This variety was sampled for the first time this week. Firmness is testing an average of 18.4, close to 18, the range for long term CA storage. Starch conversion for the five sites tested an average of 2.8, already over 2.5, which is considered to be the threshold for internally mature. However, two of the five sites sampled are still testing immature. This variety appears to be ahead of the predicted harvest date, which is Oct. 3 for central Berrien County.

Red Delicious – Sampled Sept. 13, 2021

Site

Firmness

(lbs)

Red color range

(%)

Starch

 

Soluble Solids

(°Brix)

1

17.2

80-90

4.0

10.2

2

18.0

98-100

3.0

9.1

3

18.4

85-98

2.0

10.7

4

20.2

100

3.0

11.2

5

18.2

80-98

2.2

10.0

Average

18.4

 

2.8

10.2

Max

20.2

 

4.0

11.2

Min

17.2

 

2.0

9.1

Recommended

18-16

 

2.5

 

Fuji

This variety was sampled for the first time and flesh firmness is testing an average of 19.6 pounds, somewhat above 18, the level recommended for long term CA storage. Starch conversion tested 2.6, somewhat below the 3.0 considered to be the threshold for internally mature. Red blush ranges from 5% to 90%. Fuji has a predicted harvest date of Sept. 28 for central Berrien County. This is a much earlier predicted date (about three weeks earlier) than in past years due to a recalculation of the normal harvest date for this variety.

Fuji (Main season) – Sampled Sept. 13, 2021

Site

Firmness (lbs)

Red color range (%)

Starch

Soluble Solids (°Brix)

1

19.2

30-50

3.0

11.9

2

17.4

30-60

3.0

11.1

3

18.0

5-20

3.0

11.7

4

23.2

50-90

1.0

12.7

5

20.4

40-60

3.0

12.9

Average

19.6

 

2.6

12.1

Max

23.2

 

3.0

12.9

Min

17.4

 

1.0

11.1

Recommended

18-16

 

3.0

 

How to read the maturity tables

For each variety evaluated, each row in the data table is a different orchard block. Maximum and minimum values are the highest and lowest individual fruits evaluated for each. Recommended values are included for each variety at the bottom of the table. These suggested values for firmness and starch index were also published in a standalone table format. Firmness ranges encompass long and short-term storage recommendations.

Firmness in pounds pressure = measured with a FT Penetrometer using a 7/16 inch (11 millimeters) diameter probe, peel removed; range is for the average at each site.

Starch: 1 = no starch conversion, 8 = No starch; range is for average of the sites. Using Cornell Starch Iodine Index Chart.

Brix = % sugar measured with Atago PAL-1 Pocket Refractometer

Additional apple maturity helps

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

 

Normal and predicted 2021 peak harvest dates for apple varieties in central Berrien County in southwest Michigan based on weather data at the Southwest Michigan Research and Extension Center, Benton Harbor, MI.

Variety

Normal date SW

2020 Predicted 1st significant harvest date

2021 Predicted 1st significant harvest date

Paula Red

22-Aug

25-Aug

13-Aug

Zestar

22-Aug

25-Aug

13-Aug

Gingergold

20-Aug

23-Aug

11-Aug

Early Fuji

3-Sep

6-Sep

25-Aug

Gala

8-Sep

11-Sep

31-Aug

McIntosh

10-Sep

13-Sep

1-Sep

Honeycrisp

13-Sep

15-Sep

4-Sep

Empire

18-Sep

21-Sep

21-Sep

Jonathan

22-Sep

24-Sep

25-Sep

Jonagold

22-Sep

24-Sep

25-Sep

Fuji

25-Sep

28-Oct

28-Sep

Golden Delicious

25-Sep

27-Sep

28-Sep

Red Delicious

28-Sep

20-Sep

3-Oct

Ida Red

5-Oct

7-Oct

10-Oct

Rome

5-Oct

7-Oct

10-Oct

Braeburn

20-Oct

22-Oct

25-Oct

Goldrush

26-Oct

28-Oct

27-Oct

Please note that the predictions are for the first significant harvest date rather than peak harvest. Also note that the normal harvest date for Fuji is approximately three weeks ahead of the normal date given in previous years reports. Newer strains of Fuji have much earlier and more extensive red blush development than older strains. In the past, harvest of Fuji was delayed past optimum internal maturity to wait for better blush development. This delay has resulted in increased storage problems, including watercore and internal browning.

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