Southwest Michigan apple maturity report – Sept. 1, 2021

This is the first 2021 apple maturity report for the southwest Michigan region.

An apple cut in half about to be dipped in a watery solution.
Starch conversion test for apple maturing. Flesh regions staining blue have high starch content. The clearing of the core indicates this fruit is approaching maturity. Photo by Bill Shane, MSU Extension.

This is the first apple maturity report for the southwest Michigan region for the 2021 harvest season. Reports are sent out every week (usually on Wednesdays) following the Michigan State University Extension fruit team apple maturity calls on Wednesday morning.

How to read the maturity tables

For each variety evaluated, we provide data from our evaluations in a table. In each, a row is provided for each sample tested. This allows you to see how the varieties may be progressing in different regions or specific locations. An average is included for each variety. Maximum and minimum values are included for the highest and lowest individual fruits evaluated for each, to give a full spectrum of the maturity. 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.

Updates for this week

  • Gala – Some harvest for taffy apples where crop load was too heavy for good sizing. Internal maturity will allow spot picking for fresh.
  • Macs – This group is generally behind Gala in maturation.
  • Honeycrisp – Main season (standard) Honeycrisp are still generally immature.
  • Predicted harvest dates are based on the Maturity Model in MSU Enviroweather.
  • 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 russetting, frost rings and misshapen fruit.

Mac

Three samples were tested this week. Starch conversion is underway but not quite internally mature. Flesh firmness is still relatively high, allowing harvest to be delayed.

Sample

Firmness (lbs)

Red color range (%)

Starch (1-7)

Soluble Solids (°Brix)

1 – Ruby Mac

17.0

80 – 98%

3.2

11.0

2 – Linda Mac

16.4

30 – 55%

4.0

12.1

3 – Unknown

18.0

20 – 45%

2.0

11.2

Average

17.1

 

3.1

11.4

Max

18.0

 

4.0

12.1

Min

16.4

 

2.0

11.0

Recommended

14-16

 

5-7

 

Honeycrisp

Standard Honeycrisp is starting to show signs of starch conversion but has a way to go before internally mature. Flesh firmness for some sites is approaching 17 pounds, an indication that fruit softening is ahead of internal maturity. All samples were original Honeycrisp variety as indicated by relatively low amount of red blush ranging from 0 to 50% red blush, and all with a green background. Crop loads in the area are generally low, with a few sites with good crops. Bitter rot, a fungal disease, has been reported in one site. Refer to this starch chart (which uses a 1-6 scale and unique staining pattern) for maturity evaluation. Bitter pit is present in some sites on a few fruit.

The most recent honeycrisp virtual meetup was on the topic of harvest and postharvest management of Honeycrisp with Randy Beaudry, Chris Watkins and others. You can find the recording on the MSU Kaltura Mediaspace Website.

Standard Honeycrisp

Site

Firmness (lbs)

Red color range (%)

Starch (1-7)

Soluble Solids (°Brix)

1

19.0

0 – 30%

1.0

12.2

2

17.2

0 – 10%

1.8

10.7

3

18.0

0 – 20%

1.0

11.0

4

17.2

20 – 50%

2.0

11.9

5

18.4

10 – 30%

1.2

10.7

6

17.0

10 – 40%

1.6

10.5

Average

17.8

 

1.4

11.2

Max

19.0

 

2.0

12.2

Min

17.0

 

1.0

10.5

Recommended

15-17

 

3.5-7

 

Gala

Early strain Gala varieties have already been harvested. For standard (main season) Gala varieties, starch conversion has proceeded rapidly with six of seven sites averaging above 3.0, which is considered internally mature. Firmness is testing relatively high (18 or more pounds firmness) for six of seven sites. Red blush development is good to very good, and all had a slight green cast to the background. Good firmness will allow harvest to be delayed in most sites if needed for better color or size development.

Gala - Standard

Site

Firmness

Red color range

Starch

Soluble Solids

 

(lbs)

(%)

 

(°Brix)

1

20.4

80 – 98%

6.0

10.9

2

20.0

55 – 95%

4.2

11.5

3

19.4

50 – 95%

3.8

12.1

4

24.0

30 – 85%

2.6

12.5

5

20.0

75 – 98%

4.4

11.2

6

16.1

80 – 98%

7.2

12.4

7

18.0

70 – 95%

6.8

12.2

Average

19.7

 

5.0

11.8

Max

24.0

 

7.2

12.5

Min

16.1

 

2.6

10.9

Recommended

16-18

 

3-6

 

Apple maturity sampling parameters

  • Firmness in pounds pressure = measured with a FT Penetrometer using a 7/16” (11 mm) 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

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.

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

The normal harvest dates for other varieties are listed below for the central southwest Michigan area. The predicted dates for other non-modeled varieties are a rough estimate based on the McIntosh, Jonathan and Red Delicious predicted dates. 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.

ReTain application should be applied 30 DBH (days before harvest). Harvista can be applied three to seven DBH.

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 
southwest

2020 predicted first significant harvest date

2021 predicted first 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

Did you find this article useful?


You Might Also Be Interested In