Grand Rapids area apple maturity report – Aug. 18, 2021

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

Apples sittin in bines in a lab.
Apple maturity samples being tested at the Apple Quality Lab in Sparta, Michigan. Photo by Anna Wallis, MSU Extension.

This is the second apple maturity report 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.

For general information about how samples are collected and processed, please refer to Apple Maturity Report #1.

How to read the maturity tables

For each variety evaluated, we provide data from our evaluations in a table. In each table, 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

  • Weather: The remainder of August is expected to be warmer and drier than normal. This week, expect highs in the mid to upper-80s and lows in the mid-60s. This will have an impact on drop-susceptible fruit and stop-drop materials. In general, we need a few cooler nights for better color development and a little more precipitation (or continued irrigation) to help with fruit size. Rain is also scarce. There is a chance of isolated thunderstorms expected on Saturday, but little opportunity for rain otherwise.
  • Ginger Gold and Zestar: These early varieties are harvesting now! Maturity metrics (starch, firmness, soluble solids) indicate that some fruit is ripe, although there is a range of maturity on the tree (as is typical of these varieties). In these varieties, look for a change in background color from green to green/yellow and development of varietal flavor.
  • Paula Red is beginning harvest.
  • Wildfire Gala is harvesting now. Standard strains (Buckeye, Brookfield) still need time.
  • Premier Honeycrisp is beginning harvest this week. Other varieties are still approximately three to four weeks away from harvest.
  • 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.

Ginger Gold

Variety

Location

Fruit Weight (g)

Ethylene (% >0.2ppm)

Red Color (%)

Background color

Firmness (lbs)

Starch

Soluble Solids (°Brix)

Notes

Ginger Gold

Ridge1

200

20%

na

3.6

17.8

2.0

10.7

minor stem russet, seeds white

Average

 

200

20%

na

3.6

17.8

2.0

10.7

 

Max

 

 

 

na

4.0

21.1

3.0

 

 

Min

 

 

 

na

3.0

16.1

1.0

 

 

Recommended*

 

 

 

na

2.0

16-18

2.0-3.0

11-12

 

Zestar

Variety

 

Location

 

Fruit Weight

(g)

Ethylene

(% >0.2ppm)

Red Color

(%)

Background color

 

Firmness

(lbs)

Starch

 

Soluble Solids

(°Brix)

Notes

 

Zestar

Ridge1

110

70%

36.0

3.6

13.3

3.2

12.0

 

Average

 

110

70%

36.0

3.6

13.3

3.2

12.0

 

Max

 

 

 

60.0

4.0

15.7

4.0

 

 

Min

 

 

 

10.0

3.0

11.3

2.0

 

 

Recommended

 

 

 

60-85

2.0

12-14

3.5-6.5

12-13

 

Paula Red

Paula’s are mature or nearly mature, although there is a wide range of maturity within orchard blocks. Harvest has started in most places. Fruit has very good size and color is adequate. Some very mild water core was observed in a few fruit. Some minor frost damage in the form of russeting is apparent.

The main indicators for this variety are starch approximately 3.0 and firmness between 15-16 pounds. Stems will also loosen on the tree.

Mild watercore in apple fruit
Mild watercore evident in a few fruit.

Variety

Location

Fruit
weight 
(g)

Ethylene 
(% >0.2ppm)

Red
color 
(%)

Background
color

Firmness
(lbs)

Starch

Soluble Solids
(°Brix)

Notes

Paula Red

Standale2

200

.

76.5

5.0

15.8

5.0

12.7

minor russetting and watercore

Paula Red

Standale3

190

.

72.5

4.9

15.1

3.5

12.9

mild watercore

Paula Red

Ridge1

160

.

82.5

4.0

15.2

3.0

12.0

mild watercore, seeds ~75% brown

Paula Red

Ridge4

180

90%

67.0

4.9

15.3

4.0

11.9

 

Paula Red

Belding2

200

.

67.5

4.5

14.6

3.8

11.8

some ridging and lopsided fruit

Average

 

186

90%

73.2

4.6

15.2

3.9

12.3

 

Max

 

 

 

95.0

5.0

18.9

5.0

12.9

 

Min

 

 

 

40.0

3.5

10.6

2.0

11.8

 

Recommended

 

 

 

90.0

4.0

15-16

3.0

 

 

Ruby Mac

One sample was taken this week as an early evaluation. 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 just started.

Variety

Location

Fruit
Weight 
(g)

Ethylene
(% >0.2ppm)

Red
Color 
(%)

Background
color

Firmness
(lbs)

Starch

Soluble Solids
(°Brix)

Notes

Ruby Mac

Ridge4

130

0%

76.0

5.0

17.3

3.0

10.3

 

Average

 

130

0%

76.0

5.0

17.3

3.0

10.3

 

Max

 

 

 

90.0

5.0

20.3

4.0

 

 

Min

 

 

 

50.0

5.0

15.0

2.0

 

 

Recommended

 

 

 

 

 

14-16

5-7

 

 

Honeycrisp

Premier Honeycrisp is beginning harvest now. As expected, there is a very broad range of maturity within blocks and trees.

Standard Honeycrisp harvest is still approximately three to four weeks until harvest. All fruit 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. Starch in this variety shows a considerably different pattern than other varieties. Refer to this starch chart (which uses a 1-6 scale and unique staining pattern) for maturity evaluation. Some fruit is already very large in size, although highly dependent on crop load, which is considerably variable this season. Some frost damage is apparent in the form of russetting or other damage to fruit finish. In addition, sunburn was detected in two blocks in the form of necrotic, depressed flesh tissue. Bitter pit was detected in a couple of fruits in one location; in this location fruit was considerably larger and crop lighter than other locations.

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 in order 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. You can find the recording on the MSU Kaltura Mediaspace Website.

Apples with sunburn damage
Fruit with sunburn damage.
One fruit with bitter pit already expressing.
One fruit with bitter pit already expressing.
Apple cores
Standard Honeycrisp (left) showing no starch clearing (one starch pattern); Premier Honeycrisp (right) showing considerable starch clearing and variation in fruit ripeness.

Premier Honeycrisp

Variety

Location

Fruit
Weight 
(g)

Ethylene
(% >0.2ppm)

Red
Color 
(%)

Background
color

Firmness
(lbs)

Starch

Soluble Solids
(°Brix)

Notes

Honeycrisp - Premier

Ridge1

263

80%

53.0

3.2

14.3

3.9

12.9

 

Average

 

263

80%

53.0

3.2

14.3

3.9

12.9

 

Max

 

 

 

80.0

4.0

17.7

6.0

 

 

Min

 

 

 

40.0

3.0

10.8

1.5

 

 

Recommended

 

 

 

 

 

14-16

5-7

 

 

Standard Honeycrisp

Variety

Location

Fruit
Weight 
(g)

Ethylene 
(% >0.2ppm)

Red Color (%)

Background color

Firmness (lbs)

Starch

Soluble Solids (°Brix)

Notes

Standard

Standale1

288

10%

16.5

4.0

18.4

1.0

4.3

mild russet, one fruit with bitter pit

Standard

Standale2

275

20%

19.5

4.0

18.7

1.0

22.1

variable size

Standard

Belding1

213

.

34.0

3.9

20.0

1.0

12.0

russet (frost damage)

Standard

Belding2

225

.

31.0

3.9

21.4

1.0

10.4

 

Standard

Belding3

213

.

34.0

4.0

21.1

1.0

10.7

mild russet

Standard

Ridge1

225

10%

26.0

3.7

21.2

1.0

10.9

 

Standard

Ridge3

213

.

44.0

3.7

20.4

1.0

11.1

 

Standard

Ridge4

219

0%

20.5

4.0

19.8

1.0

10.6

 

Average

 

218

10%

31.6

3.9

20.7

1.0

11.0

 

Max

 

 

20%

80.0

4.0

28.9

6.0

22.1

 

Min

 

 

0%

5.0

3.0

10.8

1.0

4.3

 

Recommended

 

 

 

 

 

15-17

3.5-7

 

 

Gala

Early strains (e.g., ‘Wildfire’) are picking now or will begin this week in most locations. Wildfire matures approximately two weeks ahead of standard strains. Color is acceptable in most locations.

Other standard strains (e.g., Brookfield and Buckeye) are not close yet. All fruit 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 while other locations were still very green, and 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. Some frost damage is apparent in blocks in the form of russeting, lopsided fruit, and ridging.

ReTain has been applied to most blocks at this point. Below, several untreated locations are separated from treated blocks. At this time, very little difference was detected between treated and untreated fruit samples.

Wildfire Gala

Variety

Location

Fruit
Weight 
(g)

Ethylene
(% >0.2ppm)

Red
Color 
(%)

Background
color

Firmness
(lbs)

Starch

Soluble Solids
(°Brix)

Notes

Gala - Wildfire

Ridge1

175

100%

93.8

3.0

17.1

5.8

14.6

minor stem cracking, seeds 50% brown

Average

 

175

100%

93.8

3.0

17.1

5.8

14.6

 

Max

 

 

 

95.0

3.0

20.3

7.0

 

 

Min

 

 

 

90.0

3.0

14.7

3.0

 

 

Recommended

 

 

 

 

 

14-16

5-7

 

 

Gala – No ReTain

Strain

Location

Fruit
Weight 
(g)

Ethylene
(% >0.2ppm)

Red
Color 
(%)

Background
color

Firmness
(lbs)

Starch

Soluble Solids 
(°Brix)

Notes

Brookfield

Standale1

160

90%

42.5

3.7

20.4

1.3

12.2

russet (frost damage)

Brookfield

Ridge2

140

0%

83.0

3.7

22.5

1.0

10.4

 

Buckeye

Ridge3

140

.

50.5

3.8

24.0

1.0

9.9

 

Average

 

140

45%

66.8

3.8

23.3

1.0

10.2

 

Max

 

 

100%

90.0

4.0

28.4

2.0

12.2

 

Min

 

 

0%

10.0

3.0

19.2

1.0

9.9

 

Recommended

 

 

 

 

 

16-18

3-6

 

 

Gala – ReTain applied

Strain

Location

Fruit
Weight 
(g)

Ethylene
(% >0.2ppm)

Red
Color 
(%)

Background
color

Firmness
(lbs)

Starch

Soluble Solids
(°Brix)

Notes

Brookfield

Standale2

140

0%

37.5

4.9

24.0

1.0

10.5

 

Brookfield

Ridge3

170

.

48.5

3.7

25.2

1.0

11.3

ridging (frost damage)

Brookfield

Ridge4

140

.

57.0

3.5

21.9

1.0

10.1

 

Brookfield

Belding1

170

.

48.0

3.9

21.3

1.0

9.1

 

Galaxy

Belding2

150

.

40.0

3.7

21.9

1.0

10.3

 

Buckeye

Belding2

150

.

82.5

3.9

20.9

1.0

9.6

 

Brookfield

Belding3

140

.

67.5

3.8

24.8

1.0

10.5

 

Average

 

153

0%

57.3

3.8

22.7

1.0

10.2

 

Max

 

 

 

95.0

5.0

29.6

7.0

14.6

 

Min

 

 

 

10.0

3.0

3.6

1.0

9.1

 

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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