West central Michigan apple maturity report – September 13, 2023
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EmailGrowers began picking early Gala varieties this week. Honeycrisp is rapidly maturing, and Empire is still immature.
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 beginning harvest of early Gala and Honeycrisp this week. Some growers have also harvested September Wonder Fuji. McIntosh strains such as Jonamac, RubyMac and standard McIntosh are at a similar stage of maturity and could be picked for mid-term storage. Empire was tested for the first time this week, and fruit are still immature. Honeycrisp are maturing faster than expected this season. Growers may need to apply Harvista to help slow down maturity.
Weather update
Weather over the past week has been cool with a mix of rain and sun. Daytime temperatures have ranged from the 60s to 70s, and nighttime temperatures have been in the mid-40s to upper 60s. Ideal temperatures for red color development are highs in the upper 70s and lows in the upper 50s. 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 Sept. 12, the MSU Enviroweather station for Hart has reported an accumulation of 3,311 growing degree days (GDD) base 42 and 2,178 GDD50. Scattered rainfall occurred on Monday, Sept. 11, across the region. The Hart Enviroweather station reported a total of 0.30 inches of rainfall on Sept.11 and 12. This is much needed rain as soil moisture levels continue to be dry this season in the west central region.
As a reminder, rainfall over 2 inches can wash off fungicide residues on fruit. Growers should maintain fungicide coverage to minimize late season rots, particularly for fruit that will be in long-term storage. Excessive rain may also have an impact on fruit by temporarily diluting flavor and brix (sugars).
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 samples of Brookfield Gala and Pacific Gala were collected at three locations on Sept. 11 in Oceana County. Generally, fruit is ready for harvest, and some growers have started harvesting Gala this week. Fruit size is improving and will increase with recent rain events. Red color was enhanced since last week, and some blocks are highly colored depending on the Gala strain. Background color is changing to yellow. Fruit are still firm with an average of 19.5 pounds. Sugars are increasing, and fruit starch is still low at 1.9. Starch is being converted to sugar at the core. Fruit are ready for harvest for long-term controlled atmosphere storage.
|
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) |
Honeycrisp
Fruit were sampled from three locations on Sept. 11 in Oceana County. Fruit are sizing well. Red color development is at 71% which has improved from last week. Background color is light green, and fruit firmness is 13.2 pounds. Starch clearing is at an average of 6.3. Sugar levels are similar to last week and are considered good according to the Brix table below. Honeycrisp are maturing faster than expected. Consider spraying Harvista to slow maturity to manage risk of overripe fruit.
Bitter pit has been observed in some locations. Fruit that are high risk or are more susceptible to bitter pit development may be in blocks with younger trees, high-risk rootstocks or high-vigor trees. Large fruit are also more susceptible to bitter pit development than small fruit. Fruit with high risk of bitter pit should be cooled quickly to the recommended 38 degrees Fahrenheit storage temperature, as conditioning will exacerbate bitter pit. High risk fruit should be marketed as soon as possible. Fruit intended for longer-term storage should be pre-conditioned, with recommended conditions of 50-60 F for five to seven days. MSU Extension has more recommendations for Honeycrisp conditioning and storage.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 5 |
203.1 (187-226) |
64.8 (40-85) |
4.0 (5-3) |
15.6 (12-18) |
5.0 (2-8) |
13.0 (11.2-14.4) |
|
Sept. 11 |
219 (221-217) |
71 (90-45) |
3.0 (4-2) |
13.2 (14.75-12.05) |
6.3 (7-4) |
12.7 (14.4-11.0) |
McIntosh
Fruit were sampled from three locations on Sept. 11 in Oceana County. McIntosh strains included this week are Jonamac, Ruby Mac and the standard McIntosh. Red color is increasing, and background color has changed slightly and is light green. Fruit firmness has decreased from last week. On average, starch clearing is moderate, and sugars levels are similar to last week. Fruit are ready for harvest for mid-term controlled atmosophere storage.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Aug. 28 |
157 (153-161) |
61.5 (95-40) |
5 (4-5) |
15.9 (14-18) |
2.5 (2-4) |
12.0 |
|
Sept. 5 |
137 (113-155) |
86.0 (55-98) |
4.4 (5-3) |
16.0 (13-20) |
3.4 (2-5) |
13.2 (13.1-13.7) |
|
Sept. 11 |
151.6 (168.5-127) |
83.1 (100-40) |
3.86 (5-3) |
15.02 (18.65-13.05) |
4.03 (6-2) |
12.9 |
Empire
Fruit were sampled at two locations on Sept. 11 in Oceana County. Fruit are still immature, and red color 73.5%. Background color is green, and starch is clearing in the core. Sugar levels are fair at 11.6 Brix.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 11 |
143 (166-120) |
73.5 (90-50) |
3.95 (4-3) |
17.135 (18.5-15.75) |
2.15 (3-1) |
11.6 |
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 |
