West central Michigan apple maturity report – September 18, 2024

Emily Lavely<lavelyem@msu.edu>, Michigan State University Extension -

Jonagold are being harvested in the west central region. High daytime temperatures mean apples are continuing to mature ahead of schedule.

Idared apple trees.
Figure 1. Idared trees in Mears, Michigan, on Sept. 16. Photo by Emily Lavely, MSU Extension.

In the west central region, harvest of September Wonder Fuji, Jonagold and Empire is wrapping up. Mutsu, Idared (Figure 1) and Golden Delicious were tested for maturity this week. Dry and sunny days have allowed growers to continue harvesting through varieties as they mature. Some Mutsu had water core this week.

Weather over the past week has been unusually hot with above normal temperatures in the 80s and weekend temperatures close to 90 degrees Fahrenheit. High temperatures will remain in the 80s over the next few days and will cool down into the 70s this weekend and into next week. There is little rain in the forecast so conditions will be hot and dry over the next few days with some possibility of rain forecasted for Sunday. Using harvest management tools is recommended for varieties that will be mature soon.

How to read maturity tables

Each week, an apple maturity report will be provided and will include average values for several apple samples for varieties nearing maturity. Maximum and minimum values are included in tables below for the highest and lowest individual fruits evaluated for each to give a full spectrum of maturity. All samples included in the reports have been untreated with ReTain or Harvista, unless otherwise noted. Samples were collected from two to five locations across Oceana County (Figures 2-3).

Golden Delicious, Idared, Mutsu and Red Delicious apples.
Figure 2. Apple varieties tested Sept. 9 for apple maturity in Oceana County. Photo by Emily Lavely, MSU Extension.

For more information about apple maturity testing, review these resources compiled by the Michigan State University Extension tree fruit team.

Maturity information for the west central region

Red Delicious, Idared, Rome and Golden Delicious apples in cartons cut in half and applied with iodine for starch testing.
Figure 3. Starch staining for apple varieties harvested on Sept. 16. Photo by Emily Lavely, MSU Extension.

Rome

Fruit were sampled at two locations in Oceana County this week. Fruit will mature soon at some locations. Rome is considered mature at a starch rating of 3. Fruit are dark red with percent coverage at 95%, similar to last week. Fruit firmness decreased slightly, and fruit is still very firm at 21.8 pounds (lbs) pressure. Starch is 2.4, and sugars are similar to last week at 10.4 degrees Brix.

Collection Date

Fruit Weight (g)

Red Color (%)

Background color (5-1)

Firmness (lbs)

Starch (1-8)

Soluble Solids (°Brix)

Sept 9

173 (188-159)

96 (100-60)

3.1 (4-1)

25.5 (29.4-21.6)

1.8 (3-1)

10.5 (11.0-9.9)

Sept 16

192 (194-189)

95 (100-60)

3.3 (4-1)

21.8 (26.3-19.1)

2.4 (3-1)

10.4 (11.0-9.8)

Mutsu/Crispin

Fruit were sampled at two locations in Oceana County this week. Fruit are still immature. There is some blush although fruit are still green. Background color is light green, and firmness is similar to last week at 18.8 lbs pressure. Starch is 2.2, and sugars are 12.3 Brix.

Collection Date

Fruit Weight (g)

Red Color (%)

Background color (5-1)

Firmness (lbs)

Starch (1-8)

Soluble Solids (°Brix)

Sept 9

301 (343-259)

25 (45-2)

4.8 (5-4)

18.6 (21.5-16.1)

1.9 (3-1)

11.3 (11.5-11.1)

Sept 16

328 (346-311)

31 (50-0)

4.7 (5-4)

18.8 (21.1-17.0)

2.2 (7-1)

12.3 (12.9-11.7)

Golden Delicious

Fruit were sampled at five locations in Oceana County this week. Fruit are mature at some locations and are light green. Some blush was observed this week. Firmness is 16.9 lbs pressure, and recommended pressure for long-term storage is 17. Starch is 2.9, and fruit are considered mature at a starch rating of 3. Sugars have increased and are excellent at 13 Brix according to the table below.

Collection Date

Fruit Weight (g)

Red Color (%)

Background color (5-1)

Firmness (lbs)

Starch (1-8)

Soluble Solids (°Brix)

Sept 9

170 (190-142)

27 (60-0)

4.0 (5-2)

18.0 (21.0-15.1)

1.7 (4-1)

12.5 (12.6-12.3)

Sept 16

190 (250-158)

28 (50-0)

3.7 (5-2)

16.9 (22-12.8)

2.9 (5-1)

13.0 (13.9-12.0)

Red Delicious

Fruit were sampled at three locations in Oceana County this week. Fruit are still immature, and red color development is at 98%. Background color is yellow green, and firmness is 17.7 lbs pressure. Pressure recommended for long-term storage is 18 lbs. Starch is 1.7, and sugars are 10.3 Brix. Red delicious are considered mature with a starch rating of 2.5.

Collection Date

Fruit Weight (g)

Red Color (%)

Background color (5-1)

Firmness (lbs)

Starch (1-8)

Soluble Solids (°Brix)

Sept 9

151 (180-122)

98 (100-95)

1.4 (3-1)

18.2 (21.9-16.0)

1.4 (2-1)

10.0 (10.3-9.7)

Sept 16

165 (179-156)

97 (100-70)

2.2 (4-1)

17.7 (20.5-16.2)

1.7 (5-1)

10.3 (11.2-9.7)

Idared

Fruit were sampled at three locations in Oceana County this week. Fruit are immature. Red color development is at 75%. Background color is light green, and firmness is 18.4 lbs pressure. Pressure recommended for long-term storage is 16 lbs, and fruit are considered mature with a starch rating of 3.5. Starch is 1.9, and sugars are 11.4 Brix.

Collection Date

Fruit Weight (g)

Red Color (%)

Background color (5-1)

Firmness (lbs)

Starch (1-8)

Soluble Solids (°Brix)

Sept 16

197 (260-167)

75 (99-50)

3.7 (4-3)

18.4 (21.6-14.3)

1.9 (3-1)

11.4 (12.4-10.6)

Ambrosia

Fruit were sampled at two locations in Oceana County this week. Fruit are immature. Red color development is at 56%, and fruit have a beautiful pink blush. Background color is light green, and firmness is 18.2 lbs pressure. Starch is 2.2, and sugars are 11.6 Brix. Fruit can mature quickly so it may be important to test Ambrosia blocks every few days as fruit get more mature to pick at the correct timing for optimal flavor and storage.

Collection Date

Fruit Weight (g)

Red Color (%)

Background color (5-1)

Firmness (lbs)

Starch (1-8)

Soluble Solids (°Brix)

Sept 16

220 (255-186)

56 (70-40)

3.2 (4-3)

18.2 (23.3-15.1)

2.2 (5-1)

11.6 (12.4-10.7)

Apple maturity sampling parameters

  • Color % = the visual percentage of red color from 0 to 100; range is of all fruits tested. Indicates surface area covered in red and intensity of red color.
  • 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 for Honeycrisp: will typically be rated using the standard Michigan State University starch scale (1-8). However, a separate starch chart for Honeycrisp apples developed by Washington State University (scale 1-6) also exists.
  • Brix = % sugar measured with Atago PAL-1 Pocket Refractometer

Looking for more? View Michigan State University Extension’s Apple 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

6

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

 

Brix Guide

Low

Fair

Good

Excellent

All varieties

Less than 11

11

12

13

Honeycrisp

Less than 12

12

12

Greater than 14

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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