Southwest Michigan apple maturity report – Sept. 8, 2021

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

Gala apples hanging from a tree.
Gala are being harvested rapidly in southwest Michigan. Photo by Mike Reinke, MSU Extension.

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

A brief hailstorm occurred in the late afternoon in the central southwest Michigan region on Tuesday, Sept. 7. Hail was small, soft to hard and scattered. Initial assessment is that damage to fruit was generally minor but could increase fire blight problems in orchards already struggling with this disease this season. Gala is the focus of harvesting in the area with good internal maturity. Macs are moving steadily forward but will benefit by waiting briefly for more sugar development. Main season (standard) Honeycrisp have improved, with some blocks ready for first picking. Bitter rot is becoming a significant problem in some Honeycrisp blocks.

Detailed information by variety

Mac

Starch conversion is underway but not quite internally mature. Flesh firmness varies considerably with two of the three blocks tested averaging 16 or less pounds of pressure. Harvesting will be justified over the next week. This variety is lagging slightly behind the predicted harvest date of Sept. 1, 2021.

Mac – Sampled Sept. 7, 2021

Sample

Firmness (lbs)

Red color range (%)

Starch (1-7)

Soluble Solids (°Brix)

1 – Ruby Mac

15.0

50 - 85

4.0

12.5

2 – Linda Mac

19.3

20 - 60

2.0

11.7

3 – Unknown

16.0

90 - 98

4.4

11.6

Average

16.8

 

3.5

11.9

Max

19.3

 

4.4

12.5

Min

15.0

 

2.0

11.6

Recommended

16-14

 

5.0

 

 

 Mac maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Aug. 31

17.1 (16.4-18.0)

3.1 (2.0-4.0)

11.4

Sept. 7

16.8 (15.0-19.3)

3.5 (2.0-4.4)

11.9

Honeycrisp

Standard Honeycrisp starch conversion jumped almost 2 points since last week and is averaging 3.1, with three of six sites having averages slightly exceeding the 3.5 mature threshold. Note: We are using the Cornell 1-8 scale for starch conversion for Honeycrisp in this report. Flesh firmness dropped 1 pound to an average of 16.8, still suitable for long-term controlled atmosphere (CA) storage. All samples were original Honeycrisp variety—blush is ranging from 10 to 90% red compared to last week with 0 to 50% red blush. Brix level has improved slightly. We now have three sites showing bitter rot symptoms. This fungal disease is favored by warm wet conditions. Fungicide treatments are definitely warranted to protect against further infections in sites where the disease is present. Bitter pit is present in some sites on a few fruit.

Standard Honeycrisp – Sampled Sept. 7, 2021

Site

Firmness (lbs)

Red color range (%)

Starch (1-7)

Soluble Solids (°Brix)

1

17.0

40 - 70

2.4

13.2

2

17.2

10 - 30

1.4

10.4

3

18.0

45 - 85

3.6

13.8

4

16.4

10 - 75

4.0

11.7

5

15.0

40 - 90

4.6

11.7

6

17.2

10 - 30

2.8

11.3

Average

16.8

 

3.1

12.0

Max

18.0

 

4.6

13.8

Min

15.0

 

1.4

10.4

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

Gala

Firmness is still holding at almost 20 pounds. Red blush development continues to improve. Starch indices are testing mature, and brix has jumped from 11.8 to 13.1 over the past week. Good firmness will allow harvest to be delayed in most sites if needed for better color, size or brix development, however Gala is mature and ready for harvesting, based on these samples.

Standard Gala – Sampled Sept. 7, 2021

Site

Firmness (lbs)

Red color range (%)

Starch

Soluble Solids (°Brix)

1

20.0

100

5.4

12.1

2

21.3

60 - 100

5.2

13.0

3

21.2

85 - 100

4.8

15.5

4

20.0

85 - 98

6.2

12.6

5

19.0

100

5.4

13.4

6

17.1

95 - 100

6.2

13.1

7

20.0

100

5.4

12.1

Average

19.8

 

5.5

13.1

Max

21.3

 

6.2

15.5

Min

17.1

 

4.8

12.1

Recommended

16-18

 

3-6

 

 

Gala maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Aug. 31

19.7 (16.1-24.0)

5.0 (2.6-7.2)

11.8

Sept. 7

19.8 (17.1-21.3)

5.5 (4.8-6.2)

13.1

Jonagold

Jonagold were sampled for the first time this week. The predicted harvest date is Sept. 25 for central Berrien County. Starch indices average 2.2, well below the threshold of 3.5 for this variety. Fruit firmness at 20.7 pounds is also indicating harvesting can be delayed.

Jonagold – Sampled Sept. 7, 2021

Site

Firmness (lbs)

Red color range (%)

Starch

Soluble Solids (°Brix)

1

23.0

20 - 60

1.6

13.7

2

18.2

20 - 60

2.2

12.1

3

20.0

30 - 60

2.8

12.0

4

23.3

50 - 80

1.2

14.1

5

19.0

5 - 45

3.0

11.3

Average

20.7

 

2.2

12.6

Max

23.3

 

3.0

14.1

Min

18.2

 

1.2

11.3

Recommended

17-15

 

3.5

 

Jonathan

This variety was sampled for the first time this week and is showing considerable starch conversion, now testing at an average of 3.3, just shy of the 3.5 minimum threshold. Firmness is excellent at 20 pounds, indicating harvesting can be delayed. Some Jonathan have been harvested for taffy apples.

Jonathan – Sampled Sept. 7, 2021

Site

Firmness (lbs)

Red color range (%)

Starch

Soluble Solids (°Brix)

1

21.0

45 - 95

3.8

12.7

2

20.0

50 - 98

3.0

12.0

3

19.0

50 - 85

3.0

12.0

Average

20.0

 

3.3

12.2

Max

21.0

 

3.8

12.7

Min

19.0

 

3.0

12.0

Recommended

16-14

 

3.5

 

Empire

This variety was sampled for the first time this week. Firmness is still excellent at an average of 19.4 pounds. Starch conversion is already up to 2.9, but still short of the 3.5 considered to be the threshold for internally mature, although one site was averaging 4.0 but with relatively low brix. 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. 7, 2021

Site

Firmness (lbs)

Red color range (%)

Starch

Soluble Solids (°Brix)

1

17.4

50 - 95

2.6

10.3

2

22.1

85 - 98

2.0

12.7

3

20.0

50 - 95

3.0

12.3

4

18.4

50 - 75

4.0

9.3

Average

19.4

 

2.9

11.2

Max

22.1

 

4.0

12.7

Min

17.4

 

2.0

9.3

Recommended

16-14

 

3.5

 

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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