West central Michigan apple maturity report – September 28, 2023
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EmailHoneycrisp, Jonagold and Empire are being harvested this week in the west central region. Golden Delicious are ready for harvest in some locations. IdaRed and Rome harvest is around the corner.
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 Honeycrisp, Jonagold, and Empire this week. Golden Delicious are mature and should be harvested for mid- and long-term storage. Red Delicious are now mature according to the starch index chart below and could be harvested for long-term storage. Idared and Rome starch rating is close to 3, and fruit are still very firm. Apples around the state are maturing more rapidly than expected. Growers may need to apply Harvista and ReTain to help slow down maturity and manage available labor.
Weather update
Weather over the past week has been warm with some rain. A warmup is expected going into the weekend. Sugar levels continue to be good or excellent depending on the variety.
As of Sep. 27, the Enviroweather station for Hart has reported an accumulation of 3,615 growing degree days (GDD) base 42 and 2,364 GDD base 50. Rain showers occurred on Sept. 27 with accumulation of 0.14 inches for the Hart weather station. Temperatures will be warmer for this time of year as we head into October with highs in the 70s degrees Fahrenheit and lows in the 50s F. These warm temperatures may advance apple maturity faster than normal over the next few weeks.
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
Empire
Fruit were sampled from two locations on Sept. 25 in Oceana County. Fruit are 160g in average weight and size is similar to last week. Red color development is improving. Background color is light green, and fruit firmness is 16.4 pounds which is similar to last week. The starch rating is an average of 4.8. 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 mid- and 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) |
|
Sept. 25 |
160 (165-137) |
86 (98-55) |
2.9 (4-1) |
16.4 (18.1-14.8) |
4.8 (7-4) |
12.8 (13.2-12.4) |
Golden Delicious
Fruit were sampled from three locations on Sept. 25 in Oceana County. Fruit are light green with a light blush. Fruit firmness is an average of 17.4 pounds. Starch is clearing with a rating of 5.7, and sugars levels are excellent. Fruit are ready for harvest for long-term controlled atmosphere (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) |
|
Sept. 25 |
128 (162-106) |
27 (45-0) |
3.8 (4-1) |
17.4 (19.6-14.4) |
5.7 (7-3) |
14.2 (14.7-13.5) |
Red Delicious
Fruit were sampled at three locations on Sept. 25 in Oceana County. Fruit are still immature, and red color is 98%. Background color is yellow, and firmness is at 17.4 pounds. Starch is starting to clear in the flesh. Sugar levels have improved and are at 12.1 Brix according to the table below. Fruit are ready to harvest 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 |
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) |
|
Sept. 25 |
148 (168-120) |
98 (100-80) |
1.5 (3-1) |
17.4 (19.4-15.8) |
2.9 (5-1) |
12.1 (13.4-10.4) |
Idared
Idared samples were collected at three locations on Sept. 25 in Oceana County. Fruit weight is 186 g, and red color is 69%. Background color is light green. Fruit firmness is 17.7 lbs, and starch rating is 2.9. Sugars are good at 12.4 Brix. Starch is being converted to sugar at the core. Fruit are still immature.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 25 |
186 (212-166) |
69 (98-40) |
3.6 (5-2) |
17.7 (19.3-16.4) |
2.9 (4-1) |
12.4 (12.9-12.0) |
Rome
Fruit were sampled from two locations on Sept. 25 in Oceana County. Red color development is at 95%. Background color is light green, and fruit are very firm with an average firmness of 23.1 lbs. Starch clearing is higher than expected at this stage, and the starch average rating is 3.1. Sugar levels are good according to the Brix table below. Fruit are mature according to the starch chart, but fruit firmness needs to decrease before harvest.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 25 |
153 (186-121) |
95 (100-70) |
2.4 (4-0) |
23.1 (26.3-20.3) |
3.1 (4-3) |
12.6 (13.3-11.9) |
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 |
