West central Michigan apple maturity report – September 20, 2023
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EmailGrowers are continuing to pick Gala and Honeycrisp this week. Jonagold is ready.
Apple maturity testing will occur weekly for the west central Michigan region beginning now through the end of harvest. Reports will be sent out every week following the Michigan State University Extension fruit team apple maturity calls on Wednesday mornings.
In the west central region, growers are harvesting Gala and Honeycrisp this week. Jonagold and Empire are mature and could be harvested for controlled atmosphere (CA) storage. Golden Delicious are almost mature and are still firm. Red Delicious are immature. Apple around the state are maturing more rapidly than expected. Growers may need to apply Harvista and ReTain to help slow down maturity.
Weather update
The weather over the past week has been cool and dry. A warmup is expected going into the weekend. Color development has been excellent over the past week. Bright and sunny conditions enhance photosynthesis and sugar accumulation, and sugar levels continue to be good or excellent depending on the variety.
As of Sep. 19, the MSU Enviroweather station for Hart has reported an accumulation of 3,419 growing degree days (GDD) base 42 and 2,233 GDD base 50. A chance of showers are predicted for later today, Sept. 20.
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 three to five locations across Oceana County.
For more information about apple maturity testing, review these resources compiled by the MSU Extension tree fruit team.
- Predicted apple harvest dates for 2023 from MSU Extension.
- More information on harvest management tools and timings can be found in this article.
- Guidelines from MSU Extension to check for apple maturity in your own orchard, including specific pressure and starch recommendations by variety.
- Predicting apple maturity and starch chart from Cornell University.
- Starch chart for Honeycrisp apples developed by Washington State University.
Maturity information for the west central region
Gala
Early Gala samples were collected at two locations on Sept. 18 in Oceana County. Many growers have harvested gala for long- and short-term storage. Fruit is ready for harvest for fresh eating. Fruit size and color continue to improve. Background color is yellow. Fruit firmness is decreasing with an average of 16.3 pounds. Sugars are increasing, and fruit starch is 5.6. Starch is being converted to sugar at the core.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Aug. 28 |
135 (131-141) |
59 (35-90 |
3.8 (2-5) |
21 (17-25) |
1.2 (1-2) |
10.9 (10-11.4) |
|
Sept. 5 |
160 (146-175) |
77 (40-100) |
2.8 (1-4) |
19.5 (16-23) |
1.9 (1-4) |
11.6 (11-12) |
|
Sept. 11 |
159 (167-154) |
89 (98-65) |
2.2 (3-2) |
18.3 (20.6-15.2) |
3.1 (6-1) |
12.6 (13.1-12.4) |
|
Sept. 18 |
197 (217-177) |
79 (98-45) |
1.3 (2-1) |
16.3 (18.9-13.8) |
5.6 (7-2) |
13.4 |
Jonagold
Fruit were sampled from three locations on Sept. 18 in Oceana County. Fruit are sizing well. Red color development is at 87%. Background color is light green, and fruit are firm with an average firmness of 15.7 pounds. Starch clearing is higher than expected at this stage, and the starch average rating is 5.0. Sugar levels are excellent at 13 according to the Brix table below. Jonagold fruit are maturing faster than expected. Fruit are mature and ready for short-term CA storage as suggested by the chart below.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 18 |
199 (223-174) |
87 (95-70) |
3.6 (5-3) |
15.7 (18.0-13.6) |
5.0 (7-3) |
13 (13.8-12.2) |
Empire
Fruit were sampled from three locations on Sept. 18 in Oceana County. Fruit are 164 grams in average weight and are improving in size. Red color development is similar to last week. Background color is light green, and fruit firmness is 15.9 pounds. The starch rating is an average of 3.7. Sugar levels increased slightly from last week and are considered good according to the Brix table below. Fruit are considered mature and could be picked for long-term storage.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 11 |
143 (166-120) |
74 (90-50) |
4.0 (4-3) |
17.1 (18.5-15.8) |
2.2 (3-1) |
11.6 (11.7-11.4) |
|
Sept. 18 |
164 (178-148) |
74 (90-45) |
3.5 (4-3) |
15.9 (17.7-14.4) |
3.7 (6-2) |
12.0 (12.3-11.3) |
Golden Delicious
Fruit were sampled from three locations on Sept. 18 in Oceana County. Fruit are still green with a light blush. Fruit firmness is an average of 19.0 pounds. Starch is clearing with a rating of 3.5, and sugars levels are excellent. Fruit are ready for harvest for mid-term CA storage. Depending on the block, fruit are considered mature according to the starch reading, but firmness is higher than the recommendation for long-term CA storage.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 18 |
125 (138-109) |
21 (40-5) |
4.2 (5-3) |
19.0 (21.6-16.2) |
3.5 (6-1) |
13.6 (14.3-13.2) |
Red Delicious
Fruit were sampled at three locations on Sept. 18 in Oceana County. Fruit are still immature, and red color is 92%. Background color is light green where observed, and starch is clearing in the core. Sugar levels are low at 10.6 Brix according to the table below. Fruit are still immature.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 18 |
148 (156-138) |
92 (100-70) |
3.3 (4-3) |
18.0 (19.6-16.0) |
1.9 (3-1) |
10.6 (11.1-10.1) |
Apple maturity sampling parameters
- Ethylene (% 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. 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: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.
- Starch for Honeycrisp: will typically be rated using the standard Cornell SPI 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 |
